Photo: Robert H. Mohlenbrock, Public domain · Wikimedia Commons

Alderleaf Buckthorn

Rhamnus alnifolia

Also called alder buckthorn, alder-leaved buckthorn, American alder buckthorn.

A low native buckthorn of fens, swamps and wet thickets, with alder-like leaves and black fruit for birds, at home in cold, limy wetlands.

Tolerates wet soilWildlife valueTolerates shade

Type: Shrub
Mature height: 2–5 ft
USDA zones: 3–7
Growth rate: Medium
Sun: Full, Part, Shade
Soil moisture: Average, Wet
Grows wild in: Stream banks, the forest understory, swamps and wet flats
Native range: 29 states, north to North Dakota, south to Tennessee and west to Oregon
List all 29
California, Connecticut, Idaho, Illinois, Indiana, Iowa, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Montana, New Hampshire, New Jersey, New York, North Dakota, Ohio, Oregon, Pennsylvania, South Dakota, Tennessee, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin and Wyoming
See what is native in your state

Hardiness zones Find your zone by ZIP code

Alderleaf buckthorn is a low, thornless native shrub of the buckthorn family, named for its alder-like leaves. It grows in limy fens, swamps, wet meadow edges and stream thickets across the northern states and Canada, and south in the mountains to Virginia and Tennessee. It is not one of the invasive buckthorns: its flowers have five sepals and no petals, where theirs have four of each. Illinois and Tennessee list it as endangered, and Maryland lists it as threatened. Plant it at the wet edge of a pond or in a fen garden, where its roots stay cool and damp.

Size, growth and what to expect

No source rates its growth, so our growth estimator treats it as a medium grower, like our Carolina buckthorn, about a foot and a half a year. It makes a low, thornless shrub of 2 to 5 feet. Its leaves are 2 to 4 inches long and finely toothed, with straight, evenly spaced veins like an alder's.

Small greenish flowers without petals open from May to July. The fruit ripens black in late summer and early fall, a round drupe about a quarter inch across with three stones, and birds eat it.

It grows wild in limy fens and swamps, riparian thickets, lake shores, wet meadow edges and moist woods. Its range runs from Newfoundland and Maine west to British Columbia and California, and south in the East to Virginia and Tennessee. NatureServe ranks it critically imperiled in Iowa, Maryland, Tennessee and Virginia, at the southern edge of its range.

How to grow Alderleaf Buckthorn

Alderleaf buckthorn grows in part shade or shade, and in the open sun of fens. It wants a moist to wet soil, and limy ground suits it well. Set plants 3 feet apart and keep them 3 feet from a wall. At its size it can go within 15 feet of overhead wires.

Saplings ship bare-root or potted. Plant them dormant, from leaf fall until bud swell, in a hole wider than the roots and no deeper. Set the crown at the soil line, put the native soil back in, and keep the mulch clear of the stems. Sow cleaned seed outdoors in late fall, just covered, so it gets about five months of cold before spring. Seedlings come up in spring, and in one nursery trial 75 percent of the seed sprouted.

Keep it watered through dry spells in its first two summers, since it grows wild in ground that stays wet. It needs no pruning.

Plants are mostly male or female, and only females bear fruit, so plant three or more seedlings for a male and a female. It is an alternate host of oat crown rust and a main host of the soybean aphid, so keep it away from oat and soybean fields. The berries are mildly poisonous to people.

Heights and zones are typical ranges for the species in cultivation; local conditions and seed source shift them.

Sources (12)