The common buckthorn is a small tree to large shrub, introduced to America from its native Europe and Asia to provide wildlife with suitable cover and habitat and as an ornamental. The common buckthorn displays an ability to grow in light or shade and in many soil types, a fact that helped the species become a naturalized plant in many portions of eastern North America. The common buckthorn has distinguishing features that you can use to recognize it.
Some buckthorns in the open can grow to heights of 22 to 25 feet, with a width of about 20 feet. Most, however, are considerably smaller and grow in bunches, growing to maximum heights of around 15 feet with a spread equal to their height. The trunk is usually no wider than 10 inches. This fast-growing plant has a rounded crown when mature.
The foliage on the common buckthorn is as long as three inches, and leaves are about an inch and a half in width, with an oval shape. The tips can be round or pointy on the ends. The edges have rough teeth along them, and the buckthorn leaves contain from three to four pairs of veins that run parallel to the margins of the leaf. Upon close inspection of these veins, you can see that they branch out from the midrib of the leaf in an alternate fashion. Buckthorn leaves are dark green, and they remain that way well into autumn before finally changing to a dull green-yellow mix.
Flowers and Fruit
The Ohio Department of Natural Resources website notes that the common buckthorn produces tiny greenish-yellow flowers of the male and female variety on separate trees. This means that only the female buckthorns will produce fruit. The flowers grow in clusters and bloom by May, after which they change on the female specimens into bunches of round green fruit. These ripen into a dark glossy black drupe that is a quarter inch across. If you examine one closely, you can see that it contains three or four tiny seeds.
The terminal buds of a large number of the twigs on common buckthorn help give the tree its name, as the buds are actually sharp spiny thorns. While the bark on the immature buckthorn tree is smooth and appears to shine in the sunlight, the bark on older trees is quite rough and scaly, although still holding onto its sheen. The bark is gray to brownish in color, with horizontal lines (lenticels) covering it. The National Park Service website reports that buckthorn's inner bark is yellowish, but that the heartwood of the tree is orange-pink.
Common buckthorn often grows in thickets, as the fruit that the trees produce typically winds up beneath the tree, germinating in the spring and creating new shoots. Buckthorn also suckers from its roots, sending up new growth in the area of the original plant. The roots are black, not deep in the ground and fibrous in nature during the first two years that a buckthorn grows. You should have little trouble pulling them out by hand.