Russian knapweed
(Rhaponticum repens (L.) Hidalgo)

Overview

Appearance

Rhaponticum repens is a perennial forb that can grow to 3 ft. (1 m) in height. Stems originate from a basal rosette of leaves. The rosette leaves can be unlobed to very lobed and are 2-4 in. (5-10 cm) long.

Foliage

Stem leaves are oblong, pinnately lobed to entire and up to 6 in. (15.2 cm) in length at the base of the stem and become smaller and less lobed toward the top.

Flowers

In summer to fall Rhaponticum repens produces flowers that are pink to purple and turn straw colored as they mature. The flower heads are approximately 0.5 in (1.2 cm) in diameter and urn shaped.

Fruit

Fruits (achenes) are ivory-colored with a tuft of hair that falls off at maturity.

Ecological Threat

Rhaponticum repens is native to Eurasia and was introduced into the United States in the early 1900’s. This species can cause chewing disease in horses.

Resources

• Element Stewardship Abstract - The Nature Conservancy
• Know Your Knapweeds - North Dakota State University
• Federal Noxious Weed Disseminules of the U.S. - USDA-APHIS
• Weed Field Guide - USDA Forest Service

Selected Images

Maps

Invasive Listing Sources

• Alaska Noxious Weeds
• Alberta Weed Control Act
• Arizona Noxious Weeds
• California Invasive Plant Council
• California Noxious Weeds
• Colorado Noxious Weeds
• Hawaii Noxious Weeds
• Idaho Noxious Weeds
• Iowa Noxious Weeds
• 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.
• Kansas Noxious Weeds
• Michigan Noxious Weeds
• Montana Noxious Weeds
• Nevada Noxious Weeds
• New Mexico Noxious Weeds
• Nonnative Invasive Species in Southern Forest and Grassland Ecosystems
• North Dakota Noxious Weeds
• Ohio Noxious Weeds
• Oregon Noxious Weeds
• Pacific Northwest Exotic Pest Plant Council, 1998
• South Carolina Plant Pest List
• Tennessee Exotic Pest Plant Council
• Utah Noxious Weeds - Contain
• Washington Noxious Weeds
• WeedUS - Database of Plants Invading Natural Areas in the United States
• Wisconsin Noxious Weeds
• Wisconsin's Invasive species rule – NR 40
• Wyoming Noxious Weeds

References