The Enemy: Common (European) buckthorn (Rhamnus cathartica) and glossy buckthorn (Frangula alnus [Rhamnus frangula])
Strategy: These buckthorns are non-native, deciduous, woody shrubs or small trees introduced to North America during the 1800s as ornamentals, hedgerow plantings, shelterbelts and wildlife habitat. Common and glossy buckthorn are deciduous shrubs or small trees that grow to about 25 feet tall. Common buckthorn has oval, dark green leaves with finely toothed margins. Small branches may be tipped with sharp spines. Glossy buckthorn can be distinguished from common buckthorn by the lack of thorns at the end of twigs and glossy or shiny leaves that lack toothed margins. Plants of both species reach seed-bearing age quickly, and both produce dark purple to black drupes (berries). They reproduce by seed but can also regrow from root-crown sprouts following top kill from fire or physical/mechanical damage.
Attack: They escaped cultivation and have aggressively invaded natural areas and forestland throughout much of the United States and Canada. Non-native buckthorn spreads through intentional plantings and through wildlife seed distribution, especially from birds. Invasive buckthorn shares similar distribution and habitat with the native alderleaf buckthorn. Care should be taken not to mistake the native alderleaf buckthorn for these non-natives, according to Celestine Duncan, of Techline Magazine. The trees will compete with native vegetation and damage valuable habitat for wildlife and livestock.
Defense: Intentional planting of these species should be avoided. According to Duncan, a 2.5 percent solution of Garlon 4 (an Ester- and oil-based product) should be mixed with an oil-based carrier (no water used in spray mix). Either applied as an basil to the lower trunk or as a cut-stump treatment. Applications should include great coverage of leaves and trunk of the trees or shrubs. For proper identification, contact your county weed superintendent.