Red oaks and white oaks, and where each belongs

Every eastern oak belongs to one of two groups, and the group tells you more about how a tree will behave in your yard than the species name does. It sets when the acorns sprout, how fast the tree grows, how it handles the worst oak disease, how long it lives and what its wood is good for. Learn the groups first, then match the species to the ground.

Telling the two groups apart

The red oak group. Leaf lobes end in a fine bristle; on the unlobed species (willow, shingle and laurel oak) a single bristle sits at the leaf tip. Acorns take two seasons to ripen, so a red oak carries tiny first-year acorns on its twigs through winter; they are bitter with tannin, and the inside of the shell is woolly. The bark is dark and furrowed. The wood has open pores, so a short length of red oak can be blown through like a straw, and it will not hold liquid.

The white oak group. Lobes are rounded or the edges toothed, with no bristles. Acorns ripen in one season, are sweeter, and have a smooth inner shell. The bark is paler and often flaky or plated. The pores are plugged with growths called tyloses, which is why white oak makes watertight barrels and once made ship hulls, and why it lasts longer on the ground.

The bristle is the reliable test, and it sorts every species below.

What the split means for a planter

• Acorns. White-group acorns sprout as soon as they hit the ground in fall, root before winter and shoot in spring, so they cannot be stored dry and should be planted the week they drop. Red-group acorns need a cold, damp winter first, and can be kept moist in a refrigerator and planted in spring. Squirrels know the difference: they eat white oak acorns on the spot and bury red oak acorns for later.
• Oak wilt. The fungus kills red-group trees within weeks or months of infection; white-group trees usually lose a limb at a time over years, and some recover. Where oak wilt is present, favor the white group, and do not prune any oak in spring or early summer, when the beetles that carry the spores are drawn to fresh cuts. Prune in the dormant season, at the collar.
• Speed and lifespan. Red oaks grow faster when young. White oaks tend to live longer; the oldest dated eastern oaks belong to the white group, and one planted well can outlast every building around it.
• Wildlife. Both groups feed everything with a mouth, but white acorns go in fall and red acorns last into winter. Plant both and the table stays set for months.

Bottomland and wet flats

Ground that floods in winter, clay that stays wet into spring, rich floodplain soil. The oaks we grow for it:

• Cherrybark oak (red group): the tallest and fastest of the southern red oaks, a straight-trunked giant for moist, fertile ground in full sun. Our line comes from a parent tree in Maryland, at the northern edge of the range. Not for a small lot.
• Swamp chestnut oak (white group): moist bottoms by preference, ordinary yard soil by tolerance, with some of the largest and sweetest acorns of any eastern oak and good fall color. Hardy to zone 5.
• Delta post oak (white group): a post oak that stands seasonal flooding on clay flats that bake in summer. For warm climates.
• Oglethorpe oak (white group): one of the rarest oaks in North America, at home on heavy, seasonally wet clay, with narrow unlobed leaves. It has grown well far north of its native stands.

Among common natives, swamp white oak and overcup oak take the wettest ground.

Dry sand and ridges

Sandhills, gravel, thin soil over rock, hilltops the hose does not reach. The trick is to accept a smaller tree that will not die.

• Sand post oak (white group): a compact post oak of the driest coastal-plain sands, gnarled and built for heat. Hardiness north of zone 6 is untested.
• Bear oak (red group): the scrub oak of pine barrens and ridge tops, a shrub or small tree that resprouts after fire and feeds an outsized number of caterpillars. Full sun and poor ground.
• Dwarf chinquapin oak (white group): a true shrub oak for dry sandy or rocky slopes that bears sweet, low-tannin acorns within a few years of planting and suckers into a low colony. The oak for a small yard.

Among common natives, post oak and blackjack oak take the poorest dry clay.

The oaks everyone knows, and what each wants

• Northern red oak (red group): deep, well-drained loam on slopes and uplands; tolerant of city conditions; fast and eventually enormous.
• White oak (white group): deep, well-drained upland soil, acidic to neutral; resents compaction, fill and root cutting, so protect it during construction.
• Bur oak (white group): the most adaptable eastern oak, from bottomland to prairie, and one of the few that shrugs off alkaline soil and drought together.
• Willow oak (red group): moist, deep, acidic to neutral soil; a bottomland tree that accepts an average lawn but not a dry ridge.
• Pin oak (red group): wet, acidic soil and little else; it turns yellow on alkaline ground.
• Scarlet oak (red group): dry, sandy, acidic uplands; the best fall color among the common oaks.
• Chestnut oak (white group): dry rocky ridges and thin soil; slow, tough and long-lived.

Common mistakes

• Pin oak on alkaline soil. The leaves yellow between the veins, the tree declines for decades, and iron treatments never fix it for long. Plant bur, chinquapin or swamp white oak instead.
• Willow oak on a dry hilltop. It is sold as tough because it tolerates average soil, but it is a bottomland tree, and on a droughty ridge it stalls and thins.
• A red oak in a small yard. A northern red or cherrybark oak wants a crown as wide as a house and becomes a problem tree within twenty years. Dwarf chinquapin, bear oak or sand post oak give you an oak that fits.
• Seed from far away. An acorn from the deep South grown in the North leafs out early and is likelier to be caught by frost; choose seed from a climate like yours.