Pollination planner

Every tree and shrub we sell is grown from seed, so no buyer can pick a male, a female or a clone. That matters for fruit and nuts. A tree that comes as separate male and female trees makes one seedling a coin toss, and a tree that cannot pollinate itself sets nothing alone. Add the trees you want and how many seedlings of each. The planner says whether that is enough for a crop, gives the odds, and takes spacing and years to the first crop from each tree's page.

Add a tree Any of the 364 trees and shrubs we grow. Add as many as you like, then set the count of each.

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Start with a tree

The verdict for each tree comes from its own page: separate male and female trees, a second unrelated tree needed, a second helpful, or one enough. When a tree is either male or female, 5 seedlings give at least a 90% chance of getting both and 6 give at least 95%, at even odds.

Every species

What each tree needs for a crop

"Plant" is the count that settles it: one for a tree that bears alone, two for one that needs or is helped by a partner unless its page asks for more, and when a tree is either male or female, the count its page asks for or the 5 that give a 90% chance of getting both. Blank where the page does not say whether one tree bears alone, and for a tree that sets little seed.

Tree	Needs	Plant	Partner within	Apart	First crop	Its page says
Alabama Azalea Rhododendron alabamense	One bears; a second improves the crop	2		5 ft		Sources disagree on whether a native azalea sets seed with its own pollen, so plant two seedlings from different parents for seed.
Alabama Croton Croton alabamensis	Not known whether one bears alone			6 ft		Each plant carries male and female flowers, so there are no male and female plants to pair.
Alabama Snow-wreath Neviusia alabamensis	Sets little seed			5 ft		Small, dry fruits form from late spring into fall, but their seeds rarely if ever ripen, and no seedling has ever been found in the wild.
Alderleaf Buckthorn Rhamnus alnifolia	Separate male and female trees	3		3 ft		Plants are mostly male or female, and only females bear fruit, so plant three or more seedlings for a male and a female.
Allegheny Chinquapin Castanea pumila	Needs a second, unrelated tree	2		12 to 15 ft	2 to 3 years (a crop in the third season)	American chinquapin does not pollinate itself, and a thicket of suckers from one root is still one plant, so plant two or more from different seed.
Allegheny Plum Prunus alleghaniensis	Needs a second, unrelated tree	2		10 ft	4 years	Plums need pollen from a second plum to set fruit, and a thicket from one root counts as one plant, so plant two or more from different seed.
Allegheny Serviceberry Amelanchier laevis	One tree bears alone	1		12 to 15 ft	2 to 3 years after planting	A single plant sets fruit, and birds will take the June crop before it fully ripens unless you net it.
American Basswood (Linden) Tilia americana	Needs a second, unrelated tree	2		30 ft	15 or more years (trees have borne at 8)	Lindens do not set seed from their own pollen, and bees and flies carry pollen between trees, so plant two or more if you want seed.
American Beautyberry Callicarpa americana	One bears; a second improves the crop	2		5 ft	2 years (first flowers)	The berries ripen in September and hold into winter unless the birds find them first. A single plant fruits on its own, and a few more of its kind nearby seem to set more fruit.
American Beech Fagus grandifolia	Needs a second, unrelated tree	2		50 ft	about 40 years (large quantities by 60)	American beech carries male and female flowers on the same tree, but a lone tree sets mostly empty nuts, so plant two trees and let the wind carry pollen between them.
American Chestnut Castanea dentata	Needs a second, unrelated tree	2	300 ft	30 ft	4 years	Viable nuts take at least two trees to cross-pollinate, so plant two or more from different seed, within 300 feet of each other.
American Crabapple Malus coronaria	One bears; a second improves the crop	2		20 ft	several years	Seedlings bloom and bear after several years, and fruit set improves with a second crabapple or apple nearby.
American Fly Honeysuckle Lonicera canadensis	Not known whether one bears alone			3 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
American Hazelnut Corylus americana	Needs a second, unrelated tree	2	50 ft	6 to 8 ft	2 to 3 years	Hazelnuts are wind-pollinated and a single bush will not set nuts, so plant two or more seedlings within 50 feet.
American Holly, select line Ilex opaca	Separate male and female trees	5 for 94%		15 ft	3 to 9 years (first flowers)	Holly is dioecious. Only females bear berries, and they need a male nearby, so plant several seedlings or add a known male.
American Hornbeam (Musclewood) Carpinus caroliniana	One tree bears alone	1		15 to 20 ft	about 15 years	Male and female catkins appear together on the same tree and the wind carries the pollen, so one tree sets seed alone.
American Mountain Ash Sorbus americana	Needs a second, unrelated tree	2		15 ft	about 15 years (the European species)	American mountain ash needs pollen from a second tree to set a good crop, and bees carry it, so plant two or more seedlings.
American Persimmon Diospyros virginiana	Separate male and female trees	5 for 94%		15 to 20 ft	4 to 9 years (heaviest crops at 25 to 50)	Most trees are male or female, so plant several seedlings for fruit. Seedlings begin bearing after about six years.
American Plum Prunus americana	Needs a second, unrelated tree	2		15 to 25 ft	3 to 5 years	Wild plum needs a second seedling nearby for good fruit set, and the crop ripens in August. Seedlings bear within three to five years.
American Smoketree Cotinus obovatus	Separate male and female trees	5 for 94%		15 ft		Most plants are male or female, though some carry both kinds of flower, and the males give the better smoke. Few fruits set, each a dry, one-seeded kernel about an eighth of an inch long.
American Snowbell Styrax americanus	Needs a second, unrelated tree	2		6 ft		American snowbell carries both male and female parts in each flower, but it may set little or no seed with its own pollen. Plant two or more from different seed, since bees carry the pollen between plants.
Arkansas Oak Quercus arkansana	Needs a second, unrelated tree	2		25 ft	17 or more years	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Arrowwood Viburnum Viburnum dentatum	Needs a second, unrelated tree	3		6 ft	3 years	Seedlings can fruit in their third year and a group crops every year after, but one plant or one cultivar alone sets little fruit, so plant three or more together.
Ashe's Magnolia Magnolia ashei	One tree bears alone	1		10 ft	3 to 4 years (first flowers)	Ashe's magnolia carries both male and female parts in each flower, and bees and beetles set seed on a lone tree.
Atlantic White Cedar Chamaecyparis thyoides	One tree bears alone	1		10 ft	3 to 5 years (first cones, in the open)	Atlantic white cedar carries male and female cones on the same tree and the wind pollinates it, so one tree bears alone.
Bald Cypress Taxodium distichum	One tree bears alone	1		20 to 30 ft		Male and female cones grow on the same tree and the wind carries the pollen, so one tree bears seed alone.
Bartram's Serviceberry Amelanchier bartramiana	One bears; a second improves the crop	2		4 ft		Some plants set seed only with pollen from another plant, so plant two or more from different seed for a crop.
Beach Plum Prunus maritima	Needs a second, unrelated tree	2		6 ft	3 to 4 years	Beach plum needs a second, unrelated seedling nearby to set fruit. Fruit ripens in late August or September. Seedlings bear within about four years.
Beaked Hazelnut Corylus cornuta	Needs a second, unrelated tree	2		6 ft		Beaked hazelnut is wind-pollinated and will not set nuts from its own pollen, so plant two or more seedlings.
Bear Huckleberry Gaylussacia ursina	One bears; a second improves the crop	2		3 ft		Its relatives box huckleberry and black huckleberry set little or no fruit with their own pollen, so plant two or more bear huckleberries from different parents for berries.
Bear Oak (Scrub Oak) Quercus ilicifolia	Needs a second, unrelated tree	2		8 to 10 ft	3 years from sprouts (in New Jersey; acorns take two seasons to ripen)	Bear oak is wind pollinated and will not set acorns from its own pollen, so plant two or more seedlings.
Bigleaf Magnolia Magnolia macrophylla	One tree bears alone	1		30 ft	12 or more years (first flowers)	Bigleaf magnolia carries both male and female parts in each flower, and bees and beetles moving between its flowers can set seed on a lone tree.
Bigleaf Snowbell Styrax grandifolius	Needs a second, unrelated tree	2		8 ft		Bigleaf snowbell carries both male and female parts in each flower, but it may set no seed with its own pollen. Plant two or more from different seed, since bees carry the pollen between plants.
Bigleaf Witch Hazel Hamamelis ovalis	Not known whether one bears alone			8 ft		Each flower carries both male and female parts, but no one has yet studied its pollinators or whether a lone plant sets seed.
Bitternut Hickory Carya cordiformis	One bears; a second improves the crop	2		40 ft	about 30 years (in quantity; about 25 by the Missouri Botanical Garden)	Male and female flowers grow on the same tree, and the male catkins usually open before the female flowers, so a second bitternut nearby improves the set.
Black Cherry Prunus serotina	Needs a second, unrelated tree	2		30 ft	5 to 10 years	Black cherry sets no seed with its own pollen, so plant two or more seedlings from different parents for a crop of cherries.
Black Chokeberry Aronia melanocarpa	One tree bears alone	1		4 ft	2 to 3 years	A single chokeberry sets fruit without a partner. Seedlings begin bearing in their second or third year, with berries ripening in late August.
Black Elderberry Sambucus canadensis	One bears; a second improves the crop	2		6 to 8 ft	2 years (first flowers, on canes in their second year)	Elderberry is partly self-fertile, but two seedlings set more fruit.
Black Gum (Tupelo) Nyssa sylvatica	Separate male and female trees	5 for 94%		20 ft		Most trees are male or female, so only some seedlings will fruit.
Black Hickory Carya texana	One bears; a second improves the crop	2		30 ft		Male and female flowers grow on the same tree. Hickories are mostly cross-pollinated, and a tree's own pollen sets fewer and poorer nuts, so plant two or set it near other hickories.
Black Huckleberry Gaylussacia baccata	Needs a second, unrelated tree	2		2 to 3 ft	a few years after planting	Black huckleberry appears to need pollen from another plant to set fruit, so plant two or more seedlings from different parents.
Black Locust Robinia pseudoacacia	One bears; a second improves the crop	2		20 ft	about 6 years	Bees carry the pollen, and a lone black locust can set seed with its own, but more of those seeds abort. A second tree nearby improves the crop.
Black Maple Acer nigrum	One bears; a second improves the crop	2		50 ft	about 30 years	Male and female flowers grow on the same tree, and wind and bees carry the pollen. A tree sheds its pollen either before or after its own female flowers are ready, so a second black maple nearby improves the seed crop.
Black Oak Quercus velutina	Needs a second, unrelated tree	2		50 ft	about 20 years (best at 40 to 75; good crops every 2 to 3 years)	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Black Walnut Juglans nigra	One bears; a second improves the crop	2		30 to 60 ft	about 10 years (a few nuts at 4 to 6; large crops from 20 to 30)	A lone black walnut can set nuts from its own pollen, but its catkins usually shed when its own flowers are not ready. A second walnut nearby improves the crop.
Blackhaw Viburnum Viburnum prunifolium	One bears; a second improves the crop	2		10 ft	8 to 10 years	Fruit set is heavier with a second, unrelated plant nearby, so put in two if you want the sweet blue-black fruit.
Blackjack Oak Quercus marilandica	Needs a second, unrelated tree	2		20 ft	3 to 4 years from sprouts (on burned ground; it bears younger than many oaks)	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Bladdernut Staphylea trifolia	Needs a second, unrelated tree	2				Bladdernut will not set seed with its own pollen, and a suckering patch is still one plant, so plant two or more seedlings from different parents.
Blue Ash Fraxinus quadrangulata	Not known whether one bears alone			50 ft	about 25 years	Unlike most ashes, blue ash usually carries male and female parts in each flower, and few trees are only male or female. The wind carries the pollen.
Blue Ridge St. John's-wort Hypericum buckleyi	Not known whether one bears alone			2 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Blueberry Hawthorn Crataegus brachyacantha	One bears; a second improves the crop	2		20 ft		Some blueberry hawthorns carry two sets of chromosomes and need another tree's pollen, while others carry three and can set seed alone. Plant two or more for a reliable crop.
Bluejack Oak Quercus incana	Needs a second, unrelated tree	2		25 ft		The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Bluff Oak Quercus austrina	Needs a second, unrelated tree	2		30 ft		Oaks are wind pollinated, and an acorn crop wants another oak nearby.
Bog Spicebush Lindera subcoriacea	Separate male and female trees	3 to 5		5 ft		Male and female flowers grow on separate plants and only females carry berries, so plant three to five seedlings to get both.
Bottlebrush Buckeye Aesculus parviflora	One tree bears alone	1		5 ft	about 3 years (first flowers)	Bottlebrush buckeye sets seed with its own pollen, so one plant can bear alone; bees and butterflies carry pollen from its many male flowers to the few with both parts.
Box Huckleberry Gaylussacia brachycera	Needs a second, unrelated tree	2		2 ft		Box huckleberry cannot set seed with its own pollen, and most wild patches are one plant, so plant two or more seedlings from different parents for berries.
Boynton Oak Quercus boyntonii	Needs a second, unrelated tree	2		10 ft		The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Bracted Arrowwood Viburnum bracteatum	Needs a second, unrelated tree	2		6 ft		Its close relative, our arrowwood viburnum, needs pollen from another plant to set fruit, so plant two or more seedlings from different parents.
Bristly Locust (Rose Locust) Robinia hispida	Sets little seed			5 to 15 ft	about 2 years	It seldom sets seed, spreading instead by root suckers, which holds a bank and overruns a border.
Broom Crowberry Corema conradii	Separate male and female trees	3		2 ft		Plants are male or female, and only females bear fruit, so plant three or more seedlings for a male and a female.
Buckthorn Bully Sideroxylon lycioides	One tree bears alone	1		20 ft		Each flower carries both male and female parts, and most buckthorns can pollinate themselves, so a single tree can set fruit.
Buckwheat Tree Cliftonia monophylla	Not known whether one bears alone			8 ft		Each flower carries both male and female parts, so there are no male and female trees to pair.
Bur Oak Quercus macrocarpa	Needs a second, unrelated tree	2		60 ft	about 35 years (good crops every 2 to 3 years)	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Butternut Juglans cinerea	One bears; a second improves the crop	2		40 ft	about 20 years (best from 30 to 60)	Male and female flowers grow on the same tree but seldom open together, and a lone tree with no other butternut nearby may set few nuts. Plant two or more for a crop.
Buttonbush Cephalanthus occidentalis	One bears; a second improves the crop	2		4 ft		Each flower carries both male and female parts. Buttonbush sets little seed with its own pollen and far more with pollen from another plant, so plant two or more seedlings from different parents for seed.
Canada Buffaloberry Shepherdia canadensis	Separate male and female trees	3		5 ft	4 to 6 years	Plants are male or female, and only females bear fruit, so plant three or more seedlings for a male and a female.
Canada Plum Prunus nigra	Needs a second, unrelated tree	2		15 ft	4 to 6 years	Plums need pollen from a second plum to set fruit, and a thicket from one root counts as one tree, so plant two or more from different seed.
Canada Yew Taxus canadensis	One bears; a second improves the crop	2		4 ft		Canada yew usually carries male and female cones on the same plant and the wind pollinates it, so one plant can bear alone, though plants set more seed with neighbors close by.
Carolina Bog Laurel Kalmia carolina	One tree bears alone	1		3 ft		Carolina bog laurel sets fruit with its own pollen as well as a neighbor's, so one plant bears seed alone.
Carolina Buckthorn Frangula caroliniana	One tree bears alone	1				One plant will fruit on its own. Birds strip the berries as they blacken, and the fruit is not for eating.
Carolina Hemlock Tsuga caroliniana	One tree bears alone	1		15 ft	about 20 years (good crops at 25 to 30)	Carolina hemlock carries male and female cones on the same tree and sets seed with its own wind-borne pollen, so one tree bears alone.
Carolina Laurelcherry Prunus caroliniana	One tree bears alone	1		10 ft		A single tree sets fruit without a partner.
Carolina Silverbell Halesia tetraptera	Not known whether one bears alone			25 to 35 ft	a few years (first flowers; heavy flower crops from 20 to 25)	Each flower carries both male and female parts, so there are no male and female trees to pair.
Carolina St. John's-wort Hypericum nitidum	Not known whether one bears alone			5 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Catawba Rhododendron Rhododendron catawbiense	Not known whether one bears alone			8 ft		Each flower carries both male and female parts, and bees, butterflies and hummingbirds come to the flowers.
Catberry Ilex mucronata	Separate male and female trees	3		5 ft		Most plants are male or female, and only females bear the berries, so plant three or more seedlings for a male and a female.
Cedar Elm Ulmus crassifolia	Needs a second, unrelated tree	2		40 ft		Each cedar elm flower carries both male and female parts, but elms seldom set seed with their own pollen. The wind carries pollen between trees, so plant two or more if you want seed.
Chalk Maple Acer leucoderme	One bears; a second improves the crop	2		20 ft		Chalk maple is a close relative of sugar maple, whose own pollen sets few good seeds, so a second tree nearby improves the crop.
Chapman Oak Quercus chapmanii	Needs a second, unrelated tree	2		15 ft		The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Chapman's St. John's-wort Hypericum chapmanii	Not known whether one bears alone			4 ft	3 to 5 years	Each flower carries both male and female parts, so there are no male and female plants to pair.
Cherrybark Oak, Wye Island line Quercus pagoda	Needs a second, unrelated tree	2		30 ft	about 25 years	Like other oaks, cherrybark oak is wind pollinated and needs pollen from another tree to set acorns, so plant two or more seedlings.
Chestnut Oak Quercus montana	Needs a second, unrelated tree	2		50 ft	about 20 years (stump sprouts have borne at 3)	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Chickasaw Plum Prunus angustifolia	Needs a second, unrelated tree	2		15 to 25 ft	2 years	Plums need pollen from a second plum to set fruit, and a thicket from one root counts as one tree, so plant two or more from different seed.
Chinese Chestnut Castanea mollissima	Needs a second, unrelated tree	2	200 ft	35 ft	4 to 7 years	A chestnut will not pollinate itself, and a lone tree drops empty burs. Nearly every chestnut rejects its own pollen, so plant a second seedling within 200 feet.
Chinquapin Oak Quercus muehlenbergii	Needs a second, unrelated tree	2		50 ft	under 30 years	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Chokecherry Prunus virginiana	One tree bears alone	1		15 ft	3 to 4 years (first good crop)	A single tree sets fruit without a partner.
Cinnamon Clethra Clethra acuminata	Not known whether one bears alone			5 ft		Each flower carries both male and female parts, and bees are its likely pollinators, so there are no male and female plants to pair.
Clammy Locust Robinia viscosa	One bears; a second improves the crop	2		15 ft		Each flower carries both male and female parts, and bees carry the pollen. Its close relative black locust sets about half as much seed with its own pollen as with another tree's, so a second clammy locust nearby should improve the crop.
Climbing Fetterbush Pieris phillyreifolia	One tree bears alone	1		3 ft		Its relative Japanese pieris sets seed with its own pollen, so one plant should bear seed alone.
Climbing Prairie Rose Rosa setigera	Separate male and female trees	3		12 ft		Each plant is male or female, and only females bear hips, so plant three or more seedlings for a male and a female.
Clusterspike Indigobush Amorpha herbacea	One bears; a second improves the crop	2		3 ft		A lone plant sets some seed with its own pollen and more with pollen from another plant, so plant two or more seedlings from different parents.
Coastal Azalea Rhododendron atlanticum	One bears; a second improves the crop	2		3 ft	about 3 years (first flowers, in one trial)	Sources disagree on whether a native azalea sets seed with its own pollen, so plant two seedlings from different parents for seed.
Cockspur Hawthorn Crataegus crus-galli	One tree bears alone	1		20 to 35 ft	5 to 8 years (as other hawthorns)	Most cockspur hawthorns set seed with their own pollen, so one tree usually bears alone. Midges drawn by the fishy scent carry the pollen.
Common Hackberry Celtis occidentalis	One tree bears alone	1		40 to 60 ft	about 15 years	One tree carries both male and female flowers, so it fruits alone and bears most years.
Common Hoptree (Wafer Ash) Ptelea trifoliata	Separate male and female trees	3 to 5		8 to 10 ft		Most plants are male or female, and males outnumber females, so plant three to five seedlings if you want the wafers, which follow the flowers the same summer and hang until spring. Flies, wasps and small bees pollinate it, not wind.
Common Prickly Ash (Toothache Tree) Zanthoxylum americanum	Separate male and female trees	3 to 5		6 ft		Only female plants carry the red capsules, so plant three to five seedlings to be sure of a male among the females; bees work the flowers.
Conjurer's-nut Nestronia umbellula	Separate male and female trees	3		3 ft		Plants are male or female, and only females bear fruit, so plant three or more seedlings for a male and a female.
Corkwood Leitneria floridana	Separate male and female trees	3		6 ft		Most plants are male or female, and only females bear fruit, so plant three or more seedlings for a male and a female.
Creeping Blueberry Vaccinium crassifolium	One bears; a second improves the crop	2		2 ft		A mat from one plant is a single clone, and blueberries set more fruit with pollen from another plant, so plant two or more seedlings from different parents.
Creeping Juniper Juniperus horizontalis	Separate male and female trees	3		6 ft		Plants are male or female, and only females bear the berrylike cones, so plant three or more seedlings for a male and a female.
Cucumber Magnolia Magnolia acuminata	One bears; a second improves the crop	2		35 ft	about 30 years (a seedling may bloom at 12 or more)	A lone cucumber magnolia sets less seed than trees that can cross with a neighbor, so plant two or more seedlings if you want seed.
Cumberland Azalea Rhododendron cumberlandense	One bears; a second improves the crop	2		5 ft		Sources disagree on whether a native azalea sets seed with its own pollen, so plant two seedlings from different parents for seed.
Cumberland Rosemary Conradina verticillata	One bears; a second improves the crop	2		2 ft		Each flower carries both male and female parts, and bumblebees, honey bees and other large bees carry the pollen. Its own pollen sets far fewer good seeds than pollen from another plant.
Dahoon Ilex cassine	Separate male and female trees	3		8 ft		Trees are male or female, and only females bear the red berries, so plant three or more seedlings for a male and a female.
Dangleberry Gaylussacia frondosa	One bears; a second improves the crop	2		3 ft		Its flowers cannot pollinate themselves and depend on bumblebees and small bees. Its relatives set more fruit with pollen from another plant, so plant two or more seedlings from different parents.
Deerberry Vaccinium stamineum	Needs a second, unrelated tree	2		6 ft	3 to 5 years after planting (first flowers, in full sun)	Deerberry appears to need pollen from another plant to set a full crop, so plant two or more within a few yards and let the bees work. The berries ripen from August into September and hang until the birds and deer take them.
Delta Post Oak Quercus similis	Needs a second, unrelated tree	2		40 ft	about 25 years (as post oak)	The female flowers of delta post oak open about a week after its male catkins shed pollen, and only pollen from another tree sets acorns. Plant two or more seedlings.
Devil's Walking Stick Aralia spinosa	One tree bears alone	1		6 to 10 ft	3 to 4 years (first flowers)	Growth is fast, and a stem flowers first at three to four years old. The flowers are mostly perfect, so a single plant sets fruit.
Devilwood Cartrema americana	Separate male and female trees	3		10 ft		Trees are male or female, and only females bear the dark blue fruit, so plant three or more seedlings for a male and a female.
Downy Arrowwood Viburnum rafinesqueanum	Not known whether one bears alone			5 ft		Each flower carries both male and female parts, and insects carry the pollen.
Downy Hawthorn Crataegus mollis	Needs a second, unrelated tree	2		20 to 40 ft	5 to 8 years (as other hawthorns)	Downy hawthorn needs pollen from another tree to set fruit, so plant two or more from different seed. Midges drawn by the scent carry the pollen.
Downy Serviceberry Amelanchier arborea	One tree bears alone	1		10 ft	2 to 3 years after planting	Bees carry the pollen, and a single downy serviceberry sets fruit without a second tree.
Durand Oak Quercus sinuata	Needs a second, unrelated tree	2		30 ft		The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Dwarf Chinquapin Oak Quercus prinoides	One bears; a second improves the crop	2		12 ft	3 to 5 years	A lone shrub sets a light crop, so plant two or three seedlings together.
Dwarf Hackberry Celtis tenuifolia	One tree bears alone	1		15 ft		Male and female flowers grow on the same tree and can pollinate each other, so a single tree sets fruit.
Dwarf Live Oak Quercus minima	Needs a second, unrelated tree	2		3 ft	3 years	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Dwarf Pawpaw Asimina parviflora	Needs a second, unrelated tree	2		6 ft	4 to 7 years	One plant will not set fruit alone, so plant two or more from different seed.
Dwarf Tupelo Nyssa ursina	One bears; a second improves the crop	2		6 ft		Tupelo flowers are male, female or both, and sources disagree on whether one plant bears both kinds. Plant several seedlings if you want fruit.
Dwarf Witch Alder Fothergilla gardenii	Not known whether one bears alone			3 ft		Its flowers carry both male and female parts, so there are no male and female plants to pair.
Eastern Leatherwood Dirca palustris	One tree bears alone	1		4 ft		A single leatherwood sets fruit without a partner, even in a cold spring when few insects fly.
Eastern Red Cedar Juniperus virginiana	Separate male and female trees	3		12 to 24 ft	about 10 years	Trees are male or female, and only females bear the berrylike cones, so plant three or more seedlings for a male and a female.
Eastern Redbud Cercis canadensis	Needs a second, unrelated tree	2		15 to 20 ft	under 7 years (first flowers; no pods in the first year of bloom)	Redbud needs pollen from a different tree to set pods, and bees carry it, so plant two or more seedlings.
Eastern Wahoo Euonymus atropurpureus	Not known whether one bears alone			12 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Elliott's Blueberry Vaccinium elliottii	Needs a second, unrelated tree	2		6 ft		Elliott's blueberry sets little or no fruit with its own pollen, so plant two or more seedlings from different parents and let the bees carry pollen between them.
Farkleberry Vaccinium arboreum	Needs a second, unrelated tree	2		10 ft		Farkleberry sets almost no seed with its own pollen, so plant two or more seedlings from different parents for fruit.
Fevertree Pinckneya bracteata	Needs a second, unrelated tree	2		10 ft		Fevertree will not set seed with its own pollen, so plant two or more from different seed. Bumblebees and hummingbirds carry the pollen from tree to tree.
Flag Pawpaw Asimina obovata	Needs a second, unrelated tree	2		8 ft		Other pawpaws studied cannot pollinate their own flowers, so plant two or more from different seed for fruit.
Flame Azalea Rhododendron calendulaceum	One bears; a second improves the crop	2		6 ft		Sources disagree on whether a native azalea sets seed with its own pollen, so plant two seedlings from different parents for seed.
Flatwoods Plum Prunus umbellata	Needs a second, unrelated tree	2		15 ft	3 years	Plums need pollen from a second plum to set fruit, so plant two or more from different seed.
Florida Anise Illicium floridanum	Needs a second, unrelated tree	2		5 ft		Each flower carries both male and female parts, but a plant sets little or no seed with its own pollen. A thicket grown from one root counts as one plant.
Florida Bully Sideroxylon reclinatum	One tree bears alone	1		8 ft		Each flower carries both male and female parts, and most buckthorns can pollinate themselves, so a single plant can set fruit.
Florida Flame Azalea Rhododendron austrinum	One bears; a second improves the crop	2		6 ft		Sources disagree on whether a native azalea sets seed with its own pollen, so plant two seedlings from different parents for seed.
Florida Leucothoe Agarista populifolia	One bears; a second improves the crop	2		5 ft		Florida leucothoe carries both male and female parts in each flower, and bees and butterflies visit the fragrant bells. In a close relative, some plants set seed with their own pollen and others do not, so plant two or more seedlings from different parents for seed.
Florida Maple Acer floridanum	Separate male and female trees	5 for 94%		30 ft		Most trees carry only male or only female flowers, so plant several if you want seed.
Florida Swamp Privet Forestiera segregata	Separate male and female trees	3		5 ft		Plants are male or female, and only females bear fruit, so plant three or more seedlings for a male and a female.
Florida Torreya Torreya taxifolia	Separate male and female trees	3		30 ft	about 20 years	Trees are male or female, and only females bear seed, so plant three or more seedlings for a male and a female.
Florida Willow Salix floridana	Separate male and female trees	3		10 ft		Plants are male or female, and bees carry pollen from the male catkins to the female ones, so plant three or more for seed.
Florida Yew Taxus floridana	Separate male and female trees	3		12 ft		Trees are male or female, and only females bear the red fruit, so plant three or more seedlings for a male and a female.
Flowering Dogwood Cornus florida	Needs a second, unrelated tree	2		15 ft	6 years	Flowering dogwood rejects its own pollen and a lone tree's fruits often hold empty stones, so plant two or more seedlings from different parents.
Four-petal Pawpaw Asimina tetramera	Needs a second, unrelated tree	2		6 ft		Each flower is female before it turns male, so a lone plant sets little fruit, and fruit needs plants from different seed growing near each other.
Fragrant Sumac Rhus aromatica	Separate male and female trees	3		5 ft		Most plants are male or female, and only females bear the red fruit, so plant three or more seedlings for a male and a female.
Franklin Tree Franklinia alatamaha	One tree bears alone	1		12 ft	4 years (first flowers; ripe seed a year later)	A single Franklin tree sets seed, since it is self-fertile.
Fraser Fir Abies fraseri	One bears; a second improves the crop	2		15 ft	about 15 years	Each tree carries both male and female cones and the wind carries the pollen. A lone tree may bear a good crop of cones that holds little sound seed.
Fraser Magnolia Magnolia fraseri	Needs a second, unrelated tree	2		25 ft		Each flower carries both male and female parts. Even so, Fraser magnolia is among the magnolias that cannot set seed from their own pollen, so a lone tree may bear none.
Georgia Bully Sideroxylon thornei	One tree bears alone	1		8 ft		Each flower carries both male and female parts, and most buckthorns can pollinate themselves, so a single plant can set fruit.
Georgia Indigobush Amorpha georgiana	Not known whether one bears alone			3 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Georgia Oak Quercus georgiana	Needs a second, unrelated tree	2		20 ft		The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Georgia Plume Elliottia racemosa	One bears; a second improves the crop	2		10 ft		Sources disagree on whether a lone Georgia plume sets seed, since wild clones set almost none while lone garden trees have, so plant two from different parents for seed.
Godfrey's Swamp Privet Forestiera godfreyi	Separate male and female trees	3		8 ft		Plants are male or female, and only females bear fruit, so plant three or more seedlings for a male and a female.
Golden Heather Hudsonia ericoides	Not known whether one bears alone			2 ft		Each flower carries both male and female parts, and bees visit the flowers.
Golden St. John's-wort Hypericum frondosum	Not known whether one bears alone			3 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Granite Gooseberry Ribes curvatum	Not known whether one bears alone			5 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Gray Birch Betula populifolia	Needs a second, unrelated tree	2		15 ft	8 years	Male and female catkins grow on the same tree, and the wind carries the pollen. Gray birch sets almost no good seed with its own pollen, so plant two or more seedlings if you want seed.
Gray Dogwood Cornus racemosa	One tree bears alone	1		4 ft	4 to 5 years	Fruit begins at 4 or 5 years and comes every year after; each flower carries both male and female parts, so a planting of a few seedlings will fruit.
Green Hawthorn Crataegus viridis	Not known whether one bears alone			20 to 35 ft	5 to 8 years (as other hawthorns)	Its flowers carry both male and female parts, and their unpleasant scent draws the midges that pollinate them.
Gum Bumelia Sideroxylon lanuginosum	Not known whether one bears alone			20 ft		Each flower carries both male and female parts, so there are no male and female trees to pair.
Hairy Blueberry Vaccinium hirsutum	One bears; a second improves the crop	2		2 ft		A colony from one plant is a single clone, and blueberries set more fruit with pollen from another plant, so plant two or more seedlings from different parents.
Hairy Laurel Kalmia hirsuta	One bears; a second improves the crop	2		2 ft		Its relative mountain laurel sets more seed with pollen from another plant, so plant two hairy laurels from different parents for seed.
Harbison's Hawthorn Crataegus harbisonii	One tree bears alone	1		20 ft		Harbison's hawthorn has four sets of chromosomes, and hawthorns like it usually set seed with their own pollen, so one tree can bear alone.
Hercules' Club Zanthoxylum clava-herculis	Separate male and female trees	3		15 ft		Trees are male or female, and only females bear the seed pods, so plant three or more seedlings for a male and a female.
Hillside Blueberry Vaccinium pallidum	One bears; a second improves the crop	2		3 ft		A colony from one plant is a single clone, and blueberries set more fruit with pollen from another plant, so plant two or more seedlings from different parents.
Hobblebush Viburnum lantanoides	One bears; a second improves the crop	2		6 ft		Hobblebush sets few fruits with its own pollen and far more with pollen from another plant, so plant two or more seedlings from different parents for fruit.
Honeycup Zenobia pulverulenta	One tree bears alone	1		4 ft		Each flower carries both male and female parts, and a lone plant sets some seed with its own pollen. Bumble bees are its main pollinators and raise the seed set.
Hop Hornbeam Ostrya virginiana	One tree bears alone	1		12 to 24 ft	about 25 years	Male and female catkins open together on the same tree in spring and the wind carries the pollen, so one tree sets seed alone.
Hortulan Plum Prunus hortulana	Needs a second, unrelated tree	2		20 ft	3 years	Plums need pollen from a second plum to set fruit, so plant two or more from different seed.
Indigobush (False Indigo) Amorpha fruticosa	Not known whether one bears alone			6 ft	1 year after planting (transplants in seed production plots)	Each flower carries both male and female parts and bees pollinate it, so there are no male and female plants to pair.
Inkberry Ilex glabra	Separate male and female trees	3		5 ft		Inkberry plants are male or female, and only females bear the black berries, so plant a group of three or more so that a male lands among the females.
Kentucky Coffeetree Gymnocladus dioicus	Separate male and female trees	5 for 94%		50 ft	20 to 30 years	Kentucky coffeetree is dioecious, and a seedling will not show which it is until it flowers, years from now. Females drop thick pods whose raw seed is poisonous, so pick them up where children or stock reach.
Lanceleaf Buckthorn Rhamnus lanceolata	One bears; a second improves the crop	2		8 ft		Its small flowers are mostly male or female, and sources disagree on whether one plant bears both kinds, so plant several seedlings if you want fruit.
Laurel Oak Quercus hemisphaerica	Needs a second, unrelated tree	2		30 ft	15 to 20 years (large crops regularly; Silvics, laurel oak in the broad sense)	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Leadplant Amorpha canescens	Needs a second, unrelated tree	2		2 ft	about 4 years	Leadplant sets seed only with pollen from another plant, so plant two or more seedlings from different parents.
Little Walnut Juglans microcarpa	One bears; a second improves the crop	2		20 ft	15 to 20 years	Male and female flowers grow on the same tree but ripen at different times, which favors cross-pollination, so a second little walnut nearby helps.
Littlehip Hawthorn Crataegus spathulata	Needs a second, unrelated tree	2		15 to 20 ft		Littlehip hawthorn carries two sets of chromosomes, and such hawthorns reject their own pollen, so plant two or more from different seed.
Littleleaf Buckbrush Ceanothus microphyllus	Not known whether one bears alone			2 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Live Oak Quercus virginiana	Needs a second, unrelated tree	2		60 ft		The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Lloyd's St. John's-wort Hypericum lloydii	Not known whether one bears alone			2 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Loblolly Bay Gordonia lasianthus	Not known whether one bears alone			15 ft		Each flower carries both male and female parts, so there are no male and female trees to pair.
Long-stalked Holly Ilex collina	Separate male and female trees	3		6 ft		Plants are male or female, and only females bear the red fruit, so plant three or more seedlings for a male and a female.
Longleaf Pine Pinus palustris	One bears; a second improves the crop	2		30 ft	20 to 30 years after the grass stage (as few as 9 to 10 on fertile old fields)	Each tree carries both male and female cones and the wind carries the pollen, but a lone tree tends to set less seed than trees in a group.
Maleberry Lyonia ligustrina	One tree bears alone	1		6 to 8 ft		Maleberry carries both male and female parts in each flower and accepts its own pollen, so bees set seed on a lone plant.
Maple-leaf Oak Quercus acerifolia	Needs a second, unrelated tree	2		20 ft	9 years (a tree in France from 2011 seed first bore in 2020)	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Mapleleaf Viburnum Viburnum acerifolium	One bears; a second improves the crop	2		3 ft	2 to 3 years	A good crop of fruit needs a second plant that is not a clone of the first, so plant two or more seedlings.
May White Azalea Rhododendron eastmanii	One bears; a second improves the crop	2		6 ft		Sources disagree on whether a native azalea sets seed with its own pollen, so plant two seedlings from different parents for seed.
Mayhaw Crataegus aestivalis	Not known whether one bears alone			15 to 20 ft		Its flowers carry both male and female parts, and bees work them in late winter.
Mexican Plum Prunus mexicana	Needs a second, unrelated tree	2		20 ft		Plums need pollen from a second plum to set fruit, so plant two or more from different seed.
Miccosukee Gooseberry Ribes echinellum	Not known whether one bears alone			3 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Michaux's Sumac Rhus michauxii	Separate male and female trees	3		3 ft		Most plants are male or female, and only females bear the red fruit, so plant three or more seedlings for a male and a female.
Minnie-bush Rhododendron pilosum	Not known whether one bears alone			4 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Mockernut Hickory Carya tomentosa	One bears; a second improves the crop	2		40 to 60 ft	about 25 years	The first nuts come at about 25 years and then a good crop every two or three years; a tree still bears at 200. Male and female flowers share a tree but often open at different times, so plant two or set it near other hickories.
Mountain Bush-honeysuckle Diervilla rivularis	Not known whether one bears alone			4 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Mountain Camellia (Mountain Stewartia) Stewartia ovata	One tree bears alone	1				Mountain camellia carries both male and female parts in each flower, and bees carry the pollen. Most stewartias set seed with their own pollen, and even a lone tree can bear viable seed.
Mountain Doghobble Leucothoe fontanesiana	One tree bears alone	1		4 ft		Mountain doghobble carries both male and female parts in each flower, and bees and butterflies visit it. A plant sets seed with its own pollen, so one shrub bears alone.
Mountain Fetterbush Pieris floribunda	One tree bears alone	1		4 ft		Mountain fetterbush carries both male and female parts in each flower, and small bees pollinate it. Its close relative Japanese pieris sets seed with its own pollen, so one plant should bear alone.
Mountain Indigobush Amorpha glabra	Not known whether one bears alone			3 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Mountain Laurel Kalmia latifolia	One bears; a second improves the crop	2		5 ft		Mountain laurel sets some seed with its own pollen, but less than when bees bring pollen from another plant, so plant two or more if you want seed.
Mountain Maple Acer spicatum	One tree bears alone	1		15 ft		Bees carry mountain maple pollen from tree to tree, and a lone tree still sets seed, since its seeds can form without fertilization.
Mountain Sweetbells Eubotrys recurva	Not known whether one bears alone			5 ft		Each flower carries both male and female parts, and bees and butterflies visit the flowers.
Mountain Winterberry Ilex montana	Separate male and female trees	3		12 ft		Trees are male or female, and only females bear the red fruit, so plant three or more seedlings for a male and a female.
Mountain Witch Alder Fothergilla major	Not known whether one bears alone			6 ft		Its flowers carry both male and female parts, so there are no male and female plants to pair.
Myrtle Dahoon Ilex myrtifolia	Separate male and female trees	3		8 ft		Trees are male or female, and only females bear the berries, so plant three or more seedlings for a male and a female.
Myrtle Oak Quercus myrtifolia	Needs a second, unrelated tree	2		10 ft	about 9 years	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Nannyberry Viburnum lentago	One bears; a second improves the crop	2		6 to 8 ft	8 years	For fruit, plant more than one seedling, since viburnums set far better with a second, unrelated plant nearby.
Nantucket Serviceberry Amelanchier nantucketensis	One tree bears alone	1		4 ft		A single plant sets fruit, since the species can set seed without pollination.
Netted Pawpaw Asimina reticulata	Needs a second, unrelated tree	2		3 ft		Each flower is female before it turns male and cannot pollinate itself, so plant two or more from different seed for fruit.
New Jersey Tea Ceanothus americanus	Not known whether one bears alone			3 ft	5 to 10 years	Each flower carries both male and female parts, so there are no male and female plants to pair.
Ninebark Physocarpus opulifolius	Needs a second, unrelated tree	2		6 ft	about 3 years (first flowers)	Ninebark appears to need pollen from another plant to set seed, so plant two or more seedlings from different parents if you want seed.
Northern Bayberry Morella pensylvanica	Separate male and female trees	5 to 7		4 ft	3 to 4 years	Only females carry fruit, and the pollen travels on the wind, so a male must grow nearby. One plant in five should be male, and a group of five to seven seedlings will almost always include one.
Northern Catalpa Catalpa speciosa	Needs a second, unrelated tree	2		20 ft	about 20 years	Northern catalpa sets pods only with pollen from another tree, so plant two or more seedlings for seed.
Northern Pecan Carya illinoinensis	One bears; a second improves the crop	2	250 ft	40 ft	about 10 years (10 to 20 in natural stands)	Pecans set nuts best with a second, unrelated tree nearby, because the male and female flowers on one tree open at different times. Seedling trees bear in roughly ten years.
Northern Pin Oak Quercus ellipsoidalis	Needs a second, unrelated tree	2		40 ft	about 20 years (good crops not every year; 2 to 4 years between large crops)	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Northern Red Oak Quercus rubra	Needs a second, unrelated tree	2		50 ft	20 to 25 years (heavy from 40 to 50; good crops every 2 to 5 years)	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Northern White Cedar Thuja occidentalis	One tree bears alone	1		10 ft	about 6 years (large crops after 20 to 30)	Each tree carries both male and female cones and the wind carries the pollen. It sets seed readily with its own pollen, so one tree bears alone.
Nutmeg Hickory Carya myristiciformis	One bears; a second improves the crop	2		40 ft	about 30 years (good crops every 2 to 3 years)	Nutmeg hickory carries male and female flowers on the same tree. Like other hickories, it sheds its pollen on the wind, often before or after its own female flowers are ready, so a second hickory nearby improves the crop.
Nuttall Oak Quercus texana	Needs a second, unrelated tree	2		40 ft	about 5 years (good crops from about 20, every 3 to 4 years)	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Oconee Azalea Rhododendron flammeum	One bears; a second improves the crop	2		6 ft		Sources disagree on whether a native azalea sets seed with its own pollen, so plant two seedlings from different parents for seed.
Odorless Bayberry Morella inodora	Separate male and female trees	3		8 ft		Most plants are male or female, and only females bear fruit, so plant three or more seedlings for a male and a female.
Ogeechee Tupelo Nyssa ogeche	Separate male and female trees	3		25 ft	about 5 years (seedlings on a Florida lake shore bore a good crop at 3)	Trees are male or female, and only females bear the red fruit, so plant three or more seedlings for a male and a female.
Oglethorpe Oak Quercus oglethorpensis	Needs a second, unrelated tree	2		30 to 40 ft		Oaks are wind pollinated and need pollen from another tree to set acorns, and an isolated Oglethorpe oak sets fewer. Plant two or more seedlings.
Ohio Buckeye Aesculus glabra	One tree bears alone	1		30 ft	8 years	Each flower cluster carries male flowers and flowers with both male and female parts. Its close relatives set seed as well with their own pollen as with another tree's, so one tree should bear alone.
Ouachita Indigobush Amorpha ouachitensis	Not known whether one bears alone			3 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Overcup Oak Quercus lyrata	Needs a second, unrelated tree	2		40 ft	about 25 years	Like other oaks, overcup oak is wind pollinated and needs pollen from another tree to set acorns, so plant two or more seedlings.
Ozark Chinquapin Castanea ozarkensis	Needs a second, unrelated tree	2		15 ft	3 to 5 years	Chinquapins do not set nuts from their own pollen, so plant two or more from different seed.
Ozark Witch Hazel Hamamelis vernalis	Not known whether one bears alone			8 ft	about 4 years after planting (first flowers)	Each flower carries both male and female parts, so there are no male and female plants to pair.
Pagoda Dogwood Cornus alternifolia	Not known whether one bears alone			20 ft	2 to 6 years	Each flower carries both male and female parts, so there are no male and female trees to pair.
Painted Buckeye Aesculus sylvatica	One bears; a second improves the crop	2		10 ft	8 years	Bees pollinate painted buckeye flowers. In related horse chestnuts most seed comes from crosses between trees, though a tree's own pollen sets some, so a second tree nearby improves the crop.
Parsley Hawthorn Crataegus marshallii	Needs a second, unrelated tree	2		12 to 24 ft	5 to 8 years (as other hawthorns)	Parsley hawthorn needs pollen from another tree to set fruit, so plant two or more from different seed. Native bees work the flowers.
Pawpaw Asimina triloba	Needs a second, unrelated tree	2		8 to 10 ft	5 to 8 years	Pawpaw will not pollinate itself, so plant at least two seedlings from different parents. Flies and beetles carry the pollen, and a paintbrush moved between trees sets more fruit. Seedlings bear in five to eight years.
Pear Hawthorn Crataegus calpodendron	Needs a second, unrelated tree	2		15 ft		Most pear hawthorns reproduce sexually, and such hawthorns reject their own pollen, so plant two or more from different seed.
Piedmont Azalea Rhododendron canescens	One bears; a second improves the crop	2		5 ft		Sources disagree on whether a native azalea sets seed with its own pollen, so plant two seedlings from different parents for seed.
Piedmont Rhododendron Rhododendron minus	One bears; a second improves the crop	2		5 ft		Piedmont rhododendron carries both male and female parts in each flower, but each flower sheds its pollen days before it is ready to receive pollen, so bees must carry it. Plant two or more seedlings from different parents for a fuller set of seed.
Pignut Hickory Carya glabra	One bears; a second improves the crop	2		25 to 40 ft	about 30 years (in quantity)	Seedling trees bear in quantity at about 30 years, a good crop every year or two. Male catkins and female flowers share a tree, the catkins usually shedding first, so a second hickory nearby improves the set.
Pin Cherry Prunus pensylvanica	One tree bears alone	1		15 ft	2 years	A single tree sets fruit without a partner. Trees can bear from their second year.
Pin Oak Quercus palustris	Needs a second, unrelated tree	2		40 ft	15 to 20 years (open-grown trees first)	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Pinkshell Azalea Rhododendron vaseyi	One bears; a second improves the crop	2		6 ft		Sources disagree on whether a native azalea sets seed with its own pollen, so plant two seedlings from different parents for seed.
Pinxterbloom Azalea Rhododendron periclymenoides	One bears; a second improves the crop	2		5 ft		Sources disagree on whether a native azalea sets seed with its own pollen, so plant two seedlings from different parents for seed.
Piratebush Buckleya distichophylla	Separate male and female trees	3		6 ft		Plants are male or female, and only females bear fruit, so plant three or more seedlings for a male and a female.
Plateau Live Oak Quercus fusiformis	Needs a second, unrelated tree	2		30 ft		The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Plumleaf Azalea Rhododendron prunifolium	One bears; a second improves the crop	2		6 ft		Sources disagree on whether a native azalea sets seed with its own pollen, so plant two seedlings from different parents for seed.
Pond Cypress Taxodium ascendens	Not known whether one bears alone			15 ft		Each tree carries both male and female cones.
Pond Pine Pinus serotina	One bears; a second improves the crop	2		20 ft	4 to 10 years (cone production usually from about 10)	Each tree carries both male and female cones and the wind carries the pollen, but a lone tree tends to set less seed than trees in a group.
Pondberry Lindera melissifolia	Separate male and female trees	3 to 5		4 ft	2 to 4 years (first flowers)	Male and female flowers grow on separate plants and only females carry berries, so plant three to five seedlings to get both.
Pondspice Litsea aestivalis	Separate male and female trees	3 to 5		6 ft		Male and female flowers grow on separate plants and only females carry fruit, so plant three to five seedlings to get both.
Possumhaw Ilex decidua	Separate male and female trees	3		6 ft	2 to 4 years (first flowers)	Most plants are male or female, and only females bear the red fruit, so plant three or more seedlings for a male and a female.
Possumhaw Viburnum Viburnum nudum	One bears; a second improves the crop	2		6 ft		More than one shrub gives the best crop of berries, so plant two or more together.
Post Oak Quercus stellata	Needs a second, unrelated tree	2		35 ft	about 25 years (good crops every 2 to 3 years)	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Prairie Crabapple Malus ioensis	One tree bears alone	1		20 to 30 ft		Its flowers are self-fertile, so a lone tree can set fruit.
Prairie Redroot Ceanothus herbaceus	Not known whether one bears alone			2 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Pygmy Fringetree Chionanthus pygmaeus	Separate male and female trees	5 for 94%		5 ft		Most plants are male or female, and in the wild only about one plant in seven is female, so plant several seedlings if you want fruit.
Pyramid Magnolia Magnolia pyramidata	Needs a second, unrelated tree	2		15 ft		Each flower carries both male and female parts. Even so, pyramid magnolia is among the magnolias that cannot set seed from their own pollen, so a lone tree may bear none.
Rabbiteye Blueberry Vaccinium virgatum	Needs a second, unrelated tree	2		6 ft	3 to 4 years after planting	Rabbiteyes set little fruit with their own pollen, so plant two or more seedlings from different parents for a crop.
Red Buckeye Aesculus pavia	One bears; a second improves the crop	2		10 ft	2 to 3 years (first flowers)	Each flower cluster carries male flowers and a few with both male and female parts, and hummingbirds and bees carry the pollen. A lone tree sets seed with its own pollen. In hand pollinations, though, another tree's pollen set about three times as much fruit, so a second tree nearby improves the crop.
Red Chokeberry Aronia arbutifolia	One tree bears alone	1		3 to 6 ft	2 years	One red chokeberry bears alone, because most of its seed forms without fertilization and grows into a near copy of the mother shrub.
Red Elderberry Sambucus racemosa	Needs a second, unrelated tree	2		6 ft	2 years from sprouts (first flowers)	Red elderberry sets little or no fruit with its own pollen, so plant two or more seedlings from different parents. Bees and flies carry the pollen between shrubs.
Red Hickory Carya ovalis	One bears; a second improves the crop	2		40 ft	about 30 years (in quantity)	Male and female flowers grow on the same tree, and the catkins usually open before the female flowers, so a second hickory nearby improves the crop.
Red Hills Azalea Rhododendron colemanii	One bears; a second improves the crop	2		6 ft		Sources disagree on whether a native azalea sets seed with its own pollen, so plant two seedlings from different parents for seed.
Red Mulberry Morus rubra	Separate male and female trees	3		35 ft	about 10 years (planted trees in an open field have fruited at 4)	Most red mulberries are male or female, so plant three or more seedlings for a fair chance of fruit. Fruit usually starts at about ten years, though planted trees in an open field have fruited at four.
Red Osier Dogwood Cornus sericea	Needs a second, unrelated tree	2		5 ft	3 to 4 years	Red osier dogwood sets no fruit with its own pollen, so plant two or more seedlings from different parents for a crop of berries.
Red Spruce Picea rubens	One bears; a second improves the crop	2		12 ft	15 to 20 years (once the crown reaches full light; good crops after about 30)	Each tree carries both male and female cones, and the wind carries the pollen. Much of the seed a lone tree sets with its own pollen is empty, so trees in a group bear better.
Redbay Persea borbonia	Needs a second, unrelated tree	2		25 ft		Redbay carries both male and female parts in each flower, but a tree usually needs pollen from another redbay to set seed, and bees carry most of it.
Rhodora Rhododendron canadense	One bears; a second improves the crop	2		3 ft		Sources disagree on whether a native azalea sets seed with its own pollen, so plant two seedlings from different parents for seed.
River Birch Betula nigra	Needs a second, unrelated tree	2		40 ft		Male and female catkins grow on the same tree, and the wind carries the pollen. River birch sets almost no good seed with its own pollen, so plant two or more seedlings if you want seed.
Rock Elm Ulmus thomasii	One tree bears alone	1		30 ft	about 20 years	Each flower carries both male and female parts, and rock elm is self-fertile, so a lone tree can set seed.
Rosebay Rhododendron Rhododendron maximum	One bears; a second improves the crop	2		8 ft		Rosebay rhododendron carries both male and female parts in each flower, and bees carry the pollen. A lone shrub can set seed with its own pollen, but a second shrub from a different parent sets more.
Roughleaf Dogwood Cornus drummondii	Not known whether one bears alone			6 ft	2 to 6 years	Each flower carries both male and female parts, so there are no male and female plants to pair.
Roundleaf Dogwood Cornus rugosa	Not known whether one bears alone			5 ft	2 to 6 years	Each flower carries both male and female parts, so there are no male and female plants to pair.
Roundleaf Serviceberry Amelanchier sanguinea	One bears; a second improves the crop	2		8 ft		Some plants set seed with their own pollen and others only with pollen from another plant, so plant two or more from different seed for a crop.
Runner Oak Quercus pumila	Needs a second, unrelated tree	2		6 ft		The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Rusty Blackhaw Viburnum rufidulum	One bears; a second improves the crop	2		10 ft	5 years	A good crop of fruit needs a second tree nearby, so plant two or more.
Sand Cherry Prunus pumila	One tree bears alone	1		4 ft	2 to 3 years	Sand cherry sets fruit with its own pollen, so one plant bears alone.
Sand Hickory Carya pallida	One bears; a second improves the crop	2		40 ft		Male and female flowers grow on the same tree. Hickories are mostly cross-pollinated, and a tree's own pollen sets fewer and poorer nuts, so plant two or set it near other hickories.
Sand Myrtle Kalmia buxifolia	One tree bears alone	1		4 ft		Its close relative Carolina bog laurel sets fruit with its own pollen, so one plant should bear seed alone.
Sand Pine Pinus clausa	One bears; a second improves the crop	2		15 ft	5 years	Each tree carries both male and female cones and the wind carries the pollen, but a lone tree tends to set less seed than trees in a group.
Sand Post Oak Quercus margaretta	Needs a second, unrelated tree	2			20 to 30 years	Like other oaks, sand post oak is wind pollinated and needs pollen from another tree to set acorns, so plant two or more seedlings.
Sandhill Oak Quercus inopina	Needs a second, unrelated tree	2		10 ft		The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Sarvis Holly Ilex amelanchier	Separate male and female trees	3		10 ft		Trees are male or female, and only females bear the red fruit, so plant three or more seedlings for a male and a female.
Sassafras Sassafras albidum	Separate male and female trees	3 to 5		25 to 40 ft	4 to 10 years (first flowers, usually nearer 10)	Only females fruit, and a seedling shows which it is only when it flowers, at four years in the open at the earliest and usually nearer ten, so plant three to five.
Scentless Mock Orange Philadelphus inodorus	Not known whether one bears alone			6 ft		Each flower carries both male and female parts, and bees visit the flowers, so there are no male and female plants to pair.
Schwerin's Indigobush Amorpha schwerinii	Not known whether one bears alone			5 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Scrub Hickory Carya floridana	One bears; a second improves the crop	2		20 ft		Male and female flowers grow on the same tree. Hickories can set nuts with their own pollen, but a tree's catkins and flowers often open at different times, so a second hickory nearby helps.
Scrub Plum Prunus geniculata	One bears; a second improves the crop	2		4 ft		Scrub plum sets little good seed with its own pollen, so plant two or more from different seed for fruit.
Seaside Alder Alnus maritima	One tree bears alone	1		10 ft	about 2 years (first flowers)	Seaside alder carries male and female flowers on the same shrub and the wind pollinates it, so one shrub sets seed alone.
September Elm Ulmus serotina	Needs a second, unrelated tree	2		40 ft		September elm carries both male and female parts in each flower, but elms seldom set seed with their own pollen, so plant two or more seedlings from different parents for seed.
Shadblow Serviceberry Amelanchier canadensis	One bears; a second improves the crop	2		12 to 20 ft	2 to 3 years after planting	A lone tree can set fruit with its own pollen, but a second tree from different seed raises the crop, so plant two or more.
Shagbark Hickory Carya ovata	One bears; a second improves the crop	2		50 ft	more than 10 years (in quantity at about 40)	Seedling trees bear after more than a decade, and a second tree nearby improves the crop.
Shellbark Hickory (Kingnut) Carya laciniosa	One bears; a second improves the crop	2		40 to 60 ft	about 40 years	Growth is slow; seedling trees bear at about 40 years and then a good crop about every second year, two or three bushels from a thriving tree. Male and female flowers share a tree, opening after the leaves in April and May; a second shellbark nearby gives a bigger crop of better nuts.
Shingle Oak Quercus imbricaria	Needs a second, unrelated tree	2		40 ft	about 25 years (good crops every 2 to 4 years)	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Shining Indigobush Amorpha nitens	Not known whether one bears alone			5 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Shumard Oak Quercus shumardii	Needs a second, unrelated tree	2		30 ft	about 25 years (best at about 50; good crops every 2 to 3 years)	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Silky Camellia Stewartia malacodendron	One bears; a second improves the crop	2		15 ft		Bees and butterflies visit silky camellia flowers for pollen. A related stewartia sets seed with its own pollen, so one plant can bear alone, but a second plant nearby gives a better crop.
Silky Dogwood Cornus amomum	Not known whether one bears alone			5 ft	4 to 5 years	Each flower carries both male and female parts, so there are no male and female plants to pair.
Silverleaf Hydrangea Hydrangea radiata	Needs a second, unrelated tree	2		4 ft		Silverleaf hydrangea's close relative, smooth hydrangea, sets no viable seed with its own pollen, so plant two or more seedlings from different parents if you want seed.
Slimleaf Pawpaw Asimina longifolia	Needs a second, unrelated tree	2		4 ft		Other pawpaws studied cannot pollinate their own flowers, so plant two or more from different seed for fruit.
Smooth Alder (Swamp Alder) Alnus serrulata	Needs a second, unrelated tree	2		6 ft		Smooth alder carries male and female flowers on the same shrub, but alders set little seed with their own pollen. Plant two or more from different parents so the wind can carry pollen between them.
Smooth Winterberry Ilex laevigata	Separate male and female trees	3		6 ft		Most plants are male or female, and only females bear the berries, so plant three or more seedlings for a male and a female.
Smooth-bark St. John's-wort Hypericum lissophloeus	Not known whether one bears alone			3 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Softleaf Arrowwood Viburnum molle	Not known whether one bears alone			6 ft		Each flower carries both male and female parts, and insects carry the pollen.
Sourwood Oxydendrum arboreum	Not known whether one bears alone			12 ft	4 to 5 years (first flowers)	Each flower carries both male and female parts and insects pollinate it, so there are no male and female trees to pair.
Southern Bush-honeysuckle Diervilla sessilifolia	Not known whether one bears alone			3 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Southern Catalpa Catalpa bignonioides	Not known whether one bears alone			20 ft	about 20 years	Each flower carries both male and female parts, and bees work the flowers. No study has tested whether a lone tree sets pods.
Southern Crabapple Malus angustifolia	One tree bears alone	1		12 to 24 ft	3 to 4 years	Its flowers are self-fertile, so a single tree can set fruit.
Southern Magnolia Magnolia grandiflora	One tree bears alone	1		30 ft	about 10 years (best crops from about 25)	Each flower carries both male and female parts, and beetles and bees carry the pollen. Isolated trees are known to bear cones with seed, so a lone tree can set seed.
Southern Pawpaw Asimina pygmea	Needs a second, unrelated tree	2		2 ft		Other pawpaws studied cannot pollinate their own flowers, so plant two or more from different seed for fruit.
Southern Red Oak Quercus falcata	Needs a second, unrelated tree	2		60 ft	about 25 years (heaviest at 50 to 75; good crops every 1 to 2 years)	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Southern Shagbark Hickory Carya carolinae-septentrionalis	One bears; a second improves the crop	2		40 ft	about 10 years (most from 40 to 200)	Male and female flowers grow on the same tree, and the wind carries the pollen. Shagbarks set nuts with their own pollen, but a tree's catkins and flowers often open at different times, so a second hickory nearby helps.
Spicebush Lindera benzoin	Separate male and female trees	3 to 5		6 ft	4 to 5 years	Male and female flowers grow on separate plants and only females carry berries, so plant three to five seedlings to get both.
Spruce Pine Pinus glabra	One bears; a second improves the crop	2		20 ft	about 10 years (most cones at 20 to 40)	Each tree carries both male and female cones, but a lone, poorly pollinated tree sets little viable seed.
Squashberry Viburnum edule	Not known whether one bears alone			6 ft	about 5 years	Each flower carries both male and female parts, and insects carry the pollen.
Staggerbush Lyonia mariana	One tree bears alone	1		4 ft		Its relative maleberry sets seed with its own pollen, so one plant should bear seed alone.
Staghorn Sumac Rhus typhina	Separate male and female trees	5 for 94%		6 to 12 ft	3 to 4 years	Sumac is male or female and only females carry the red fruit cones, so plant several seedlings if you want fruit.
Strawberry Bush Euonymus americanus	One tree bears alone	1		3 ft		Each flower carries both male and female parts, and a lone shrub sets seed with its own pollen. Ants carry most of its pollen.
Streambank Mock Orange Philadelphus hirsutus	Not known whether one bears alone			4 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Striped Maple Acer pensylvanicum	Separate male and female trees	5 for 94%		15 ft	11 years (first flowers)	Most striped maples carry only male or only female flowers in a given year, and a tree can switch, so plant several if you want seed.
Sugarberry Celtis laevigata	One tree bears alone	1		40 ft	about 15 years	Sugarberry carries male and female flowers on the same tree, with a few that carry both parts, and the wind pollinates it, so one tree bears alone.
Swamp Azalea Rhododendron viscosum	One tree bears alone	1		5 ft		Swamp azalea sets seed with its own pollen, so one plant bears alone, though bumblebees must carry the sticky pollen between flowers.
Swamp Chestnut Oak, select line Quercus michauxii	Needs a second, unrelated tree	2		40 ft	20 to 25 years (10 to 15 on an exceptional site)	Like other oaks, swamp chestnut oak is wind pollinated and needs pollen from another tree to set acorns, so plant two or more seedlings.
Swamp Cottonwood Populus heterophylla	Separate male and female trees	5 for 94%		40 ft	about 10 years	Trees are male or female, and only females bear the cottony seed, from about 10 years old.
Swamp Doghobble Eubotrys racemosa	Not known whether one bears alone			4 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Swamp Privet Forestiera acuminata	Separate male and female trees	3		10 ft		Trees are male or female, and only females bear fruit, so plant three or more seedlings for a male and a female.
Swamp Tupelo Nyssa biflora	Separate male and female trees	3		30 ft		Trees are male or female, and only females bear the dark blue fruit, so plant three or more seedlings for a male and a female.
Swamp White Oak Quercus bicolor	Needs a second, unrelated tree	2		50 ft	about 20 years (good crops every 3 to 5 years)	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Sweet Azalea Rhododendron arborescens	One bears; a second improves the crop	2		8 ft		Sources disagree on whether a native azalea sets seed with its own pollen, so plant two seedlings from different parents for seed.
Sweet Birch (Black Birch) Betula lenta	One bears; a second improves the crop	2		35 to 40 ft	10 to 15 years (first flowers, the catkins)	Male and female catkins share a tree and the wind carries the pollen, but the one sweet birch tested with its own pollen set no seed, so plant two or more for seed.
Sweet Pepperbush (Summersweet) Clethra alnifolia	One bears; a second improves the crop	2		4 ft		A lone sweet pepperbush sets some seed with its own pollen, but cross-pollinated flowers set more, so plant two or more seedlings if you want seed.
Sweetbay Magnolia Magnolia virginiana	One tree bears alone	1		12 to 24 ft	6 to 10 years	A single sweetbay sets seed on its own, since pollen from one of its flowers can fertilize another flower on the same tree.
Sweetleaf Symplocos tinctoria	Not known whether one bears alone			15 ft		Each flower carries both male and female parts, and how well a lone tree sets fruit is not known.
Sweetshrub Calycanthus floridus	Not known whether one bears alone			6 ft		Each flower carries both male and female parts, and beetles drawn by the fruity scent carry the pollen. Not every plant sets seed readily, and some flower heavily without fruiting.
Table Mountain Pine Pinus pungens	One bears; a second improves the crop	2		15 ft	5 to 7 years	Each tree carries both male and female cones and the wind carries the pollen, but a lone tree tends to set less seed than trees in a group.
Tamarack Larix laricina	One bears; a second improves the crop	2		20 ft	12 to 15 years (large crops from about 40)	Each tree carries both male and female cones, and the wind carries the pollen. Its own pollen yields mostly empty seed, so a lone tree bears far less sound seed than trees in a group.
Texas Red Oak Quercus buckleyi	Needs a second, unrelated tree	2		30 ft		The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Three-flower Hawthorn Crataegus triflora	One tree bears alone	1		10 ft	4 years	Most three-flower hawthorns carry three or four sets of chromosomes, and hawthorns like them usually set seed with their own pollen, so one plant can bear alone.
Titi Cyrilla racemiflora	One bears; a second improves the crop	2		8 ft		Titi carries both male and female parts in each flower and bees carry the pollen. Sources disagree on whether a lone shrub sets fertile seed, so plant two from different parents for seed.
Tough Bully Sideroxylon tenax	One tree bears alone	1		10 ft		Each flower carries both male and female parts, and most buckthorns can pollinate themselves, so a single tree can set fruit.
Toughleaf Dogwood Cornus asperifolia	Not known whether one bears alone			6 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Turkey Oak Quercus laevis	Needs a second, unrelated tree	2		15 ft		The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Two-wing Silverbell Halesia diptera	Not known whether one bears alone			20 ft		Each flower carries both male and female parts, so there are no male and female trees to pair.
Umbrella Magnolia Magnolia tripetala	One tree bears alone	1		20 ft		A single umbrella magnolia sets seed on its own, since beetles carry pollen from one of its flowers to another flower on the same tree.
Upland Swamp Privet Forestiera ligustrina	Separate male and female trees	3		5 ft		Plants are male or female, and only females bear fruit, so plant three or more seedlings for a male and a female.
Virginia Spiraea Spiraea virginiana	Needs a second, unrelated tree	2		6 ft		Virginia spiraea largely rejects its own pollen, and a patch is usually one clone, so good seed needs plants from different sources growing near each other.
Virginia Sweetspire Itea virginica	One tree bears alone	1		4 ft		Each flower carries both male and female parts, so a single plant sets seed.
Walter's Viburnum Viburnum obovatum	Not known whether one bears alone			6 ft		Each flower carries both male and female parts, so there are no male and female plants to pair.
Washington Hawthorn Crataegus phaenopyrum	Not known whether one bears alone			5 ft	5 to 8 years	The flowers can smell unpleasant, and the scent draws the midges that pollinate them.
Water Elm Planera aquatica	Not known whether one bears alone			25 ft		Male and female flowers grow on the same tree, with a few that carry both parts, so there are no male and female trees to pair.
Water Hickory Carya aquatica	One bears; a second improves the crop	2		40 ft	about 20 years (heavy crops most years)	Water hickory carries male and female flowers on the same tree. Like other hickories, it sheds its pollen on the wind, often before or after its own female flowers are ready, so a second hickory nearby improves the crop.
Water Locust Gleditsia aquatica	Separate male and female trees	5 for 94%		30 ft	about 10 years	Trees bear mostly male or mostly female flowers, with a few flowers carrying both parts, so plant several if you want seed.
Water Tupelo Nyssa aquatica	Separate male and female trees	3		30 ft	about 30 years (stump sprouts have borne at 2)	Trees are male or female, and only females bear the dark purple fruit, so plant three or more seedlings for a male and a female.
Weeping Hawthorn Crataegus lacrimata	Not known whether one bears alone			15 ft		Its flowers carry both male and female parts, so there are no male and female trees to pair.
Western Mayhaw Crataegus opaca	Not known whether one bears alone			15 to 20 ft	5 to 8 years (as other hawthorns)	Each flower carries both male and female parts, and native bees visit the early bloom.
White Fringetree Chionanthus virginicus	Separate male and female trees	5 for 94%		12 to 24 ft	several years (first flowers)	Most trees are male or female and only females bear fruit, so plant several seedlings; a tree shows which it is at first bloom, which can take several years.
White Oak Quercus alba	Needs a second, unrelated tree	2	650 ft	50 ft	about 20 years (open-grown trees; forest trees from about 50)	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
White Wicky Kalmia cuneata	One bears; a second improves the crop	2		3 ft		Its relative mountain laurel sets more seed with pollen from another plant, so plant two white wicky from different parents for seed.
Wild Black Currant Ribes americanum	One bears; a second improves the crop	2		5 to 6 ft	3 years	Each flower carries both male and female parts, and bees carry the pollen. Like its close relative the European black currant, a lone shrub sets fruit, but a second plant nearby gives a bigger crop.
Wild Hydrangea Hydrangea arborescens	One bears; a second improves the crop	2		3 ft	1 year (first flowers)	Sources disagree on whether wild hydrangea sets seed with its own pollen, so plant two or more seedlings from different parents for seed.
Willow Oak Quercus phellos	Needs a second, unrelated tree	2		25 ft	15 to 20 years (good crops nearly every year)	The flowers are wind pollinated, and an acorn crop wants another oak nearby.
Winged Elm Ulmus alata	Needs a second, unrelated tree	2		30 ft		Each winged elm flower carries both male and female parts, but elms seldom set seed with their own pollen. The wind carries pollen between trees, so plant two or more if you want seed.
Winterberry Holly Ilex verticillata	Separate male and female trees	5 for 94%	50 ft	5 ft	a few years (first flowers)	Winterberry is male or female and seedlings do not show which until first bloom, a few years in, so plant a group so that a male lands among the females. Small greenish-white flowers open in the leaf axils in June and July, and one male within 50 feet pollinates a group of females.
Witch Hazel Hamamelis virginiana	Needs a second, unrelated tree	2		10 ft	at least 6 years (first flowers)	Witch hazel sets little or no seed with its own pollen, so plant two or more seedlings from different parents. Even in wild stands, fewer than one flower in a hundred sets fruit.
Woolly Beach Heather Hudsonia tomentosa	Not known whether one bears alone			2 ft		Each flower carries both male and female parts, and bees visit the flowers for nectar.
Woolly Huckleberry Gaylussacia mosieri	One bears; a second improves the crop	2		3 ft		Its relatives box huckleberry and black huckleberry set little or no fruit with their own pollen, so plant two or more woolly huckleberries from different parents for berries.
Woolly Pawpaw Asimina incana	Needs a second, unrelated tree	2		5 ft		Other pawpaws studied cannot pollinate their own flowers, so plant two or more from different seed for fruit.
Yaupon Ilex vomitoria	Separate male and female trees	3		8 ft	4 to 7 years	Trees are male or female, and only females bear the red fruit, so plant three or more seedlings for a male and a female.
Yellow Anise Illicium parviflorum	One bears; a second improves the crop	2		5 ft		Each flower carries both male and female parts, and a lone plant sets some seed with its own pollen, though seed from a cross is larger.
Yellow Birch Betula alleghaniensis	One bears; a second improves the crop	2		60 ft	7 to 40 years (open-grown to forest)	Male and female catkins grow on the same tree and the wind carries the pollen. A lone tree sets some seed with its own pollen, but a second yellow birch nearby improves the crop.
Yellow Buckeye Aesculus flava	One bears; a second improves the crop	2		40 ft		Bees and hummingbirds visit yellow buckeye flowers for nectar. In related horse chestnuts most seed comes from crosses between trees, though a tree's own pollen sets some, so a second tree nearby improves the crop.
Yellowwood Cladrastis kentukea	One bears; a second improves the crop	2		40 ft	8 to 10 years (first flowers)	Yellowwood carries both male and female parts in each flower, and bees carry the pollen. Small, isolated stands often set few viable seeds, so plant two or more trees from different parents for seed.

How the verdict is made

Each tree's page gives its need. The need comes from the tree's own page, written from the Forest Service's silvics, the state extension services and the growers' guides. The page says whether the species carries male and female flowers on separate trees, whether it can pollinate itself, and whether a second tree improves the set. Spacing, a partner's distance and the years to the first crop are the page's own figures too.
Male and female trees are a matter of odds. When a tree is either male or female, each seedling is one or the other at even odds and shows which only at its first bloom, years in. So the planner gives the chance that a count includes both: two seedlings 50%, three 75%, four 88%, five 94%, six 97%, seven 98%.
A tree already there changes the odds. With a male within reach, or one tree of your own, a seedling only has to be the other kind. Then one seedling gives 50%, two give 75% and four give 94%.
Enough is the page's count, or 90%. A count is enough when it reaches the count the tree's page asks for, or a 90% chance where the page gives none. It is likely at 75%. Those two lines are the planner's own, not a source's.
A tree that cannot pollinate itself needs a second. The pollen must come from a genetically different tree, which any two of our seed-grown seedlings are. The partner counts within the distance the page gives, or in the same planting where it gives none.
Another oak, hickory, plum or crabapple can be the partner. Where a page accepts another tree of its kind, one in the plan counts. An oak counts only an oak of its own group, red or white, since the two groups do not cross.
The odds are a guide, not a promise. The share of males in a real seed lot is not always half: common hoptree's page notes that its males outnumber females. A lone female can sometimes set a little fruit from wild pollen.
Some pages do not say. Where a page does not say whether one tree bears alone, the planner says so rather than guess.

Each tree's need, count, spacing, partner distance and first crop come from its own page, written from the Forest Service's silvics and seed manual, the extension services and published studies. The even odds rest on a count of 1,930 American holly seedlings, 1.03 males to each female, in the Forest Service's silvics of the species. Our article Why a tree flowers but bears no fruit gives that count with the subject's other sources. Kentucky State University's pawpaw FAQ gives the rule for a tree that rejects its own pollen: "Pawpaws are generally self-incompatible, so you need two trees for cross-pollination." It adds: "Two grafted trees of the same cultivar will not cross-pollinate." A seed-grown seedling is never such a copy. The oak rule follows the University of Georgia's Warnell School of Forestry and Natural Resources (Kim D. Coder, Hybrid Oaks of Georgia, 2020). It finds hybrids rare between the major oak groups and frequent within them. An International Oak Society article by Jeroen Braakman (Hybridization in Quercus, 2017) knows of only one cross between oak sections, and none between the red and white oaks. The growth estimator shows how big each tree will be by its first crop, and the companion species tool what to plant between them.

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How the verdict is made