Appearance
Rhamnus cathartica is a deciduous shrub or small tree that can grow to 25 ft. (7.6 m) in height. The bark is dark gray and the inner bark is orange (easily seen when the tree is cut). Twigs are usually tipped with a sharp spine.

Foliage
The leaf arrangement is usually sub-opposite, but examples of opposite and/or alternate arrangements are commonly found. Leaves are dark green, oval, 1.5-3 in. (3.8-7.6 cm) long, slightly serrate with 3 to 4 pairs of curving veins and a somewhat folded tip.

Flowers
Flowering occurs in the spring, with fragrant, yellow-green, 4-petaled flowers developing in clusters of 2 to 6 near the base of the petioles. Plants are dioecious (male and female flowers occur on separate plants).

Fruit
Appearing in the fall, the small, purple to black fruit are 0.25 in. (0.6 cm) in diameter. The fruit contains 3-4 seeds. Birds and other wildlife eat the fruit and disperse the seeds.

Ecological Threat
Rhamnus cathartica invades forests, prairies, and savannas in the Midwestern United States and can form dense thickets crowding out native shrubs and understory plants. It is difficult to remove and can regenerate after cutting or burning. It is a native of Europe and was introduced into the United States as an ornamental shrub.

Resources

• Element Stewardship Abstract - The Nature Conservancy
• Nonnative Plants of Wisconsin - Wisconsin Department of Natural Resources
• Weeds Gone Wild: Alien Plant Invaders of Natural Areas - Plant Conservation Alliance
• Weed of the Week - USDA Forest Service
• Fact Sheet - Ontarios Invading Species Awareness Program
• Best Management Practices - Ontarios Invading Species Awareness Program

Selected Images

Maps

Invasive Listing Sources

• Alberta Weed Control Act
• City of Ann Arbor Michigan Parks and Recreation
• Commonwealth of Pennsylvania, Department of Conservation and Natural Resources, 1994.
• Connecticut Invasive Plant List
• Connecticut Invasive Plant Working Group
• Hoffman, R. & K. Kearns, Eds. 1997. Wisconsin manual of control recommendations for ecologically invasive plants. Wisconsin Dept. Natural Resources, Bureau of Endangered Resources. Madison, Wisconsin. 102pp.
• Illinois Exotic Weed Act
• Indiana Invasive Species Council - Invasive Plant List
• Indiana Terrestrial Plant Rule
• Invasive Plant Association of Wisconsin
• Invasive Plant Species of West Virginia
• Iowa Forest Invasive Plants
• Jil M. Swearingen, Survey of invasive plants occurring on National Park Service lands, 2000-2007
• John Randall, The Nature Conservancy, Survey of TNC Preserves, 1995.
• Kentucky Exotic Pest Plant Council - Severe Threat
• Maryland Department of Natural Resources Policy: Restriction on Planting Exotic Invasive Plants
• Maryland Invasive Species Council - Invasive Species of Concern in Maryland
• Massachusetts Invasive Plants Advisory Group List
• Massachusetts Noxious Weeds
• Massachusetts Prohibited Plant List
• Minnesota Noxious Weeds
• Montana Noxious Weeds
• National Park Service, Mid-Atlantic Exotic Plant Management Team Invasive Plant List
• National Park Service, National Capital Region Exotic Plant Management Team Invasive Plant List
• New Hampshire Invasive Species Committee. 2005. Guide to Invasive Upland Plant Species in New Hampshire. New Hampshire Department of Agriculture,  Markets and Food Plant Industry Division and New Hampshire Invasive Species Committee.
• New Hampshire Prohibited Invasive Species
• New Jersey Invasive Species Management Act
• New Jersey Invasive Species Strike Team 2017 Invasive Species List
• New York Regulated and Prohibited Invasive Species - Prohibited
• Non-Native Invasive Plants of Arlington County, Virginia
• Ohio Invasive Species Council
• Ontario’s Invading Species Awareness Program Tracked Species List
• Pennsylvania Department of Conservation and Natural Resources Invasive Plants
• Pennsylvania Noxious Weeds
• Reichard, Sarah. 1994.  Assessing the potential of invasiveness in woody plants introduced in North America. University of Washington Ph.D. dissertation.
• Rhode Island Natural History Survey
• Tennessee Exotic Pest Plant Council
• Vermont Noxious Weeds
• WeedUS - Database of Plants Invading Natural Areas in the United States
• West Virginia Invasive Species Strategic Plan and Volunteer Guidelines 2014
• West Virginia Native Plant Society, Flora West Virginia Project, and West Virginia Curatorial Database System, September 3, 1999
• Wisconsin Noxious Weeds
• Wisconsin's Invasive species rule – NR 40

References