06-26-2001 Agenda Packet - Laserfiche WebLink

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!' Minnesota Department of Agricuiture 90 West Plato Boulevard St. Paul. MN s-107-2094 Agronomy & Plant Protection Division Telephone: 612/296-8328 Fax: 612!296-7386 An MDA Pest Alert _ Buckthorn. and its Control Introduction Common buckthorn grows to a There are three buckthorn (Rhamnus) species height of 20 feet with a spreading, found growing in Minnesota: R. alnifolia or irregular crown. The bark is dwarf alder. R. cathartica called common or rough gray/brown, similar in European buckthorn and R.frangula also appearance to Prunus sp. The known by the common names glossy, fen or 3/8 inch glossy black fruit is alder buckthorn. bome in dense clusters at twig axils. Twigs have sub-opposite Of the three species, only glossy buckthorn has buds and a notable spine at tip. cultivars in the nursery trade. Cultivars noted: Leaves are elliptic. finely toothed. 'Asplenifolia' the fernleaf buckthorn, 'Colum- pointed and glossy dark green. naris' or columnar buckthorn. and 'Tallcole' Two strong diagnostic character- Rhamnus called tallhedae buckthorn. istics of buckthorn are the prolific cathartica berry clusters and leaves that stay mig"P. Species dark green on the tree well into winter. long after Dwarf alder (R. alnifolia) natives have turned color and shed their leaves. . is native to the northern half of Minnesota as far Glossy buckthorn (R.frangula) is from Europe. south as the Twin Cities. While drought tolerant its bad reputation comes It is a small shrub, four from its tendency to aggressively invade wetlands by four feet, found and moist woodlands. In height and width it is typically in tamarack Rh�am7n7us similar to common buckthorn. While leaves are alnifolia swamps and wet mead- similar in size and shape venation is pinnately ows. It is not considered invasive within its netted and buds are alternate. There is no spine at natural range. There are no selections of dwarf twig tips. The red fruit turns black at maturity and alder in the nursery trade. is consumed by birds which can Common or European buckthorn (R. cathartica) \ deposit seed great is native to Europe and was brought to Minnesota \ distances. in the mid-1800's as a hedging material. In Minnesota. it is the most problematic buckthorn. Columnar forms Readily invading woodland understories and in the nursery field/prairie edges trade are narrow Rhamnus Rhamnus.+anguia cathartica it is both drought upright to 12 feet, and shade tolerant. 'Asplenifolia' is This species is fine textured. height to 12 feet and spreading. rapidly spread by birds feeding on its fruit. It has not Rhamnus rranguia'Asolenitolia' r / /J been sold in the t nursery trade since the 19.) S. Page 1