Common buckthorn and glossy buckthorn were introduced to the United States in the 1800s as tough, hardy shrubs for the landscape. That toughness has made buckthorn aggressively invasive to the point where it is crowding out native flowers in woodland areas, forming an impenetrable understory layer, destroying wildlife habitat and causing long-term decline of forests by preventing the growth of native tree seedlings.
Buckthorn also spreads easily into savannas, prairies, abandoned fields and roadsides, forming dense thickets. In your yard, you many find buckthorn spouting up within the branches of other multi-stemmed shrubs or in a neglected corner.
Buckthorn is easiest to identify in late fall; it is the only tree or shrub still holding onto its green leaves. Common buckthorn leaves are rounded to egg-shaped with finely toothed margins. The leaves are very dark, dull to glossy green. Glossy buckthorn has dark green, glossy, oval-shaped leaves. A good way to make a positive identification of either species is to scratch the surface of a trunk or stem. If you find orange inner bark it is buckthorn.
Both species grow 10 to 25 feet tall and may be either trees or shrubs. There are separate male and female plants with only the female producing berries. In fall the berries turn black and are much loved by birds throughout the winter. Each berry contains 2-4 seeds that are poisonous to humans. The berries have a laxative effect on birds which ensures the spread of the seeds throughout the habitat. Thousands of buckthorn seedlings can sprout within the area of one mature tree.
Buckthorn is best controlled by pulling the seedlings when they are less than a half inch in diameter. It is easiest to do when the ground is moist after a good rain.
Larger trees and shrubs must be cut and immediately brushed or sprayed with an herbicide containing triclopyr such as Garlon 4 or Ortho Brush-B-Gone. Cutting the trees or shrubs without the herbicide follow-up is worse than not cutting them at all since they will re-sprout heavily with more branches than before.
Smaller trees, with less than a 6-inch diameter may be treated using the basal bark method. They need not be cut before herbicide is applied. Apply the herbicide at the base of the plant, wetting the bark from the soil-line up to about 12-15 inches. Spray so that the trunk becomes thoroughly wet, but not to the point of runoff. Each stem of the plant must be treated.
The best time of year to treat buckthorn with herbicide is late fall when the sap is flowing toward the roots.
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