Acroptilon repens, Russian Knapweed

Gardens & Landscapes, Invasive Species, Extension Master Gardener December 16, 2015 Print Friendly and PDF

Invasive Species: Acroptilon repens, Russian Knapweed

Russian knapweed is an invasive 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 to 4 in. (5 to 10 cm) long. Stem leaves are oblong, pinnately lobed to entire, and up to 6 in. (15.2 cm) in length at the base of the stem; they become smaller and less lobed toward the top. In summer to fall, Russian knapweed 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. Fruits (achenes) are ivory-colored with a tuft of hair that falls off at maturity. Russian knapweed is native to Eurasia and was introduced into the United States in the early 1900s. This species can cause chewing disease in horses.

What are invasive species and why should we be concerned about them? 


Taxonomy: Scientific and Common Names for This Species

Asterales > Asteraceae > Acroptilon repens (L.) DC.

Synonym(s): Rhaponticum repens, hardheads

Acroptilon repens - USDA PLANTS Profile

Distribution Maps

Russian knapweed - The reported distribution of this invasive species across the United States. (Source: Invasive Plant Atlas of the United States)

Up-to-the-minute distribution maps and why they are important

Reporting This Invasive Species

What is the best way and place to report the occurrence of an invasive species? 

 How to report an invasive species sighting to EDDMapS - Early Detection & Distribution Mapping System

EDDMapS - Report an invasive species to EDDMapS

Cooperative Extension Offices - Find your local Cooperative Extension office on this map provided by USDA

How to Identify

This invasive species can be identified by looking for the characteristics described in the paragraphs that follow.

Plant

An invasive perennial forb that can grow to 3 ft. (1 m) in height. Stems originate from a basal rosette of leaves.

Russian knapweed Russian knapweed
Eric Coombs, Oregon Department of Agriculture, bugwood.org Eric Coombs, Oregon Department of Agriculture, bugwood.org

Foliage

The rosette leaves can be unlobed to very lobed and are 2 to 4 in. (5 to 10 cm) long. Stem leaves are oblong, pinnately lobed to entire, and up to 6 in. (15.2 cm) in length at the base of the stem; they become smaller and less lobed toward the top.

Russian knapweed Russian knapweed
Bonnie Million, National Park Service, bugwood.org Bonnie Million, National Park Service, bugwood.org

Flower

In summer to fall, Russian knapweed 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.

Russian knapweed

Russian knapweed
Steve Dewey, Utah State University, bugwood.org

Steve Dewey, Utah State University,
bugwood.org

Fruit

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

Russian knapweed Russian knapweed
John M. Randall, The Nature Conservancy, bugwood.org Julia Scher, USDA APHIS PPQ, bugwood.org

Native Species That Resemble Russian Knapweed

Centaurea americana, American star-thistle - Images at invasive.org

American star-thistle (Centaurea americana) American star-thistle (Centaurea americana)
Karan A. Rawlins, University of Georgia,  bugwood.org Karan A. Rawlins, University of Georgia,  bugwood.org

 

Vernonia gigantea, tall ironweed - Images at invasive.org

tall ironweed tall ironweed

Bruce Ackley, The Ohio State University,
bugwood.org

Karan A. Rawlins, University of Georgia,
bugwood.org

 

Additional Images for Russian Knapweed

Russian knapweed - Images at Invasive.org

 

Learning Resources for Russian Knapweed

 

Additional Information, Biology, Control and Management Resources

Control and management recommendations vary according to individual circumstances. Location, habitat, weather, and a variety of other conditions are factors that help determine the best treatment choice. To find the safest and most effective treatment for your situation, consult your state's land-grant institution. If you will use chemicals as part of the control process, always refer to the product label.

United States Land-Grant University System - Find your land-grant university's College of Agriculture, Cooperative Extension Service, or other related partner on this map provided by USDA.

Invasives Database - Texas Invasives

Element Stewardship Abstract - The Nature Conservancy

Federal Noxious Weed Disseminules of the U.S. - USDA-APHIS

Fire Effects Information System - USDA Forest Service

Plant Factsheet - Colorado State University

Jepson Herbarium - University of California

Plant Profile - Cal-IPC


 

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.