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Invasive Alien of Virginia Spotted knapweed (Centaurea maculosa Lam.)

Description pasture, and has spread Spotted knapweed is a biennial herb throughout Canada, where it is in the aster family. It grows in tufted found from Nova Scotia to Brit- clumps, one plant giving rise to 1 to ish Columbia. It is found state- 20 slender, upright stems 1 to 3 feet wide in Virginia. in height with most branching oc- curring in the upper half. Seedlings Threats form a rosette of pinnately to bipin- Spotted knapweed shares with nately dissected leaves 4 to 8 inches many other the long. Stem leaves are pinnate low ability to colonize disturbed ar- on the stem, and become small, lin- eas. Once established it may in- ear-shaped farther up the stem. fest neighboring that White to pink or purple flowers are are relatively undisturbed or in at the end of the stems in -like good condition. Infestation heads. This species closely re- generally leads to a decline in sembles another less widespread , because the inva- invasive, short-fringed knapweed sive plant chokes out native (). Spotted vegetation. Grazing animals knapweed has been renamed by pass over it in favor of more plant taxonomists and is now known palatable native grasses and as Centaurea bierbersteinii DC. herbs. The system of this plant does not hold as well as native vegetation. Studies Spotted knapweed grows in dry ster- have monitored a significant ile, gravelly, or sandy openings such Spotted knapweed (Centaurea maculosa loss of soil on sites infested as pastures, old fields, and road- Lam.) with this species compared to sides. sites with native vegetation. though more labor intensive, hand- Distribution cutting will ensure that all flower Introduced accidentally into the Control buds are destroyed. For more infor- from Europe late last Hand-pulling, grubbing or clipping mation, contact the Virginia Depart- century, possibly mixed in with al- may provide some control of light ment of Conservation and Recreation falfa or in the ballast of ships, infestations. On sites where feasible, or the Virginia Native Plant Society spotted knapweed has spread mowing or hand-cutting early in the at the addresses listed below. throughout the Northeast and Mid- flower stage may control spotted Atlantic states, and westward to knapweed. This process must be re- Illustration from New Britton & Brown Illustrated Flora of the Northeast U.S. and Kansas and Nebraska. It has also peated over several years. are Adjacent Canada, by H.H. Gleason, New become established in the North- less likely to sprout or regrow if al- York Botanical Scientific west, where it infests overgrazed lowed to bolt before cutting. Al- Publications. Used with permission.

For more information, contact the Department of Conservation and Recreation or the Virginia Native Plant Society. Virginia Native Plant Society Blandy Experimental Farm 400 Blandy Farm Lane, Unit 2 Boyce, VA 22620 (540) 837-1600 217 Governor Street, Richmond, VA 23219 (804) 786-7951; http://www.state.va.us/~dcr/vaher.html http://www.vnps.org Jim Gilmore, Governor • John Paul Woodley, Jr., Secretary of Natural Resources • David G. Brickley, Director, Department of Conservation and Recreation Invasive Alien Plant Species of Virginia Spotted knapweed (Centaurea maculosa Lam.)

References Mission Biological Control Laboratory, and Inspection Service, Washington, D.C. Mauer, T., and M. Russo. 1985. Element Bozman Biological Control Facility. 1991. Radford, A.E., H.E. Ahles, and C.R. Bell. stewardship abstract: Centaurea maculosa, Biological control of diffuse and spotted 1968. Manual of the vascular flora of the spotted knapweed. The Nature knapweed. United States Department of carolinas. University of North Carolina Conservancy, Arlington, Virginia. , Animal and Plant Health Press, Chapel Hill.

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For more information, contact the Department of Conservation and Recreation or the Virginia Native Plant Society. Virginia Native Plant Society Blandy Experimental Farm 400 Blandy Farm Lane, Unit 2 Boyce, VA 22620 (540) 837-1600 217 Governor Street, Richmond, VA 23219 (804) 786-7951; http://www.dcr.state.va.us/dnh/ http://www.vnps.org Mark R. Warner, Governor • W. Tayloe Murphy, Jr., Secretary of Natural Resources • Joseph H. Maroon, Director, Department of Conservation and Recreation