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GREATjU RIVERlRIPW GREENING Common Buckthorn (Rhamnus cathartica), Glossy Buckthorn (Frangula alnus) Description Both common buckthorn and glossy buckthorn were introduced to North America as ornamental shrubs for use in fence rows, and as wildlife habitat. Both buckthorns were valued for their hardiness and ability to thrive in a variety of soil and light conditions. They also have a dense habit making them ideal for use as privacy hedges in densely populated urban areas. As an invasive in native habitats, common buckthorn tends to form dense, even -aged thickets, crowding and shading out native shrubs and herbs. Dense buckthorn invasions also prevent native tree and shrub regeneration. Common buckthorn is a shrub or small tree that can grow to 22 feet in height with as much as a 10" diameter trunk, although stems are typically more in the range of 2"-5" diameter. The crown of mature plants is spreading and irregular. The bark is gray to brown, rough textured when mature and may be confused with that of plum trees in the genus Prunus. When cut, the inner bark is yellow. Twigs are often tipped with a spine. In spring, dense clusters of 2 to 6, inconspicuous yellow -green, 4-petaled flowers emerge near the bases of the leaf stalks. Male and female flowers are borne on separate plants. Small black fruits about 1/4 inch in cross-section and containing 3-4 seeds, develop after blooming. Leaves are broadly oval, with toothed margins, rounded or pointed at the tip, and with 3-4 pairs of up - curved veins. The upper and lower leaf surfaces are hairless. Leaves appear dark, glossy green on the upper surface and stay green late into fall, after the leaves of most other deciduous species have fallen. Glossy buckthorn does not have a spine at its twig tips, its leaves are not toothed, and the undersides of the leaves are hairy. The trunks and stems have lighter colored lenticels. It similarly produces dark fruit on the female plants. The fruits of both species, if not eaten by birds, typically fall directly beneath the shrubs, creating a dense understory of seedlings characteristic of common buckthorn stands. The fruit is eaten by birds and mice and is known to cause a severe laxative effect, helping distribute seeds via birds, often far from the parent plant. Common buckthorn is primarily an invasive species of upland habitats, but it also occurs within wetlands. It prefers lightly shaded conditions, invading open oak woods, and wood edges; it may also be found in prairies, open fields, and wetlands. It is tolerant of many soil types; well drained sand, clay, poorly drained calcareous, neutral or alkaline, wet or dry. Common buckthorn occurs very frequently in Minnesotan forests. Management strategies vary depending on the terrain and timing of control. Glossy buckthorn prefers wetland habitats, but will grow in upland conditions as well. Initial control of glossy buckthorn should therefore occur in winter when the ground is frozen to facilitate access to all areas. Some areas will be difficult to access with equipment even in winter because of the other shrub species amongst which it grows. Mechanical On level upland areas, forestry mowing is an efficient method to remove the standing trees. If the stems are shattered close to the base and conditions after forestry mowing are very cold and dry, the wood is prone to drying out and may not be capable of resprouting. On steep slopes, brush saws can be used to cut the stems. The cut stumps should be treated immediately with herbicide. In wetland areas, brush saws will likely be needed to cut the stems. A forestry mower should be used only in areas where it will be possible to access the site for follow-up foliar treatment. Triclopyr with blue marker dye or a 50% solution of glyphosate with blue marker dye are effective for control. Areas cut by either method will require a follow-up foliar herbicide treatment, as it is likely that a percentage of the stems will resprout. Mowing repeatedly for several years, often multiple times a year, will eventually kill buckthorn. The goal is to deplete the roots of stored energy. Smaller buckthorn and seedlings will require fewer mowings.