spotted knapweed
(Centaurea stoebe ssp. micranthos)
Overview
Appearance
Centaurea stoebe ssp. micranthos is an herbaceous biennial or perennial plant that readily invades open areas. Its name is derived from the black margins of the flower bract tips which give the flower heads a spotted look.
Foliage
A basal rosette of deeply lobed leaves is produced the first year. Rosette leaves are deeply lobed, petiolate, and approximately 8 in. (20 cm) long. Flowering stems are 1-4 ft. (0.3-1.2 m) tall and branched. Stem leaves are alternate and may be slightly lobed or linear. Leaves become smaller and less lobed toward the apex.
Flowers
The small purple to pink flowers bloom in the early summer.
Fruit
Reproduction of spotted knapweed occurs solely by seed. Hundreds and/or thousands of seeds are produced. Seeds are easily distributed by wind, animals, and contaminated hay. Seeds can remain viable in the soil for up to 8 years.
Ecological Threat
Centaurea stoebe ssp. micranthos invades a wide variety of habitats including pastures, open forests, prairies, meadows, old fields, and disturbed areas. It displaces native vegetation and reduces the forage potential for wildlife and livestock. It is native to Europe and western Asia. It was accidentally introduced into North America in contaminated alfalfa and clover seed in the late 1800s.
Resources
- Program Aid - USDA APHIS PPQ
- Biology and Biological Control of Knapweed - USDA Forest Service
- Biological Control of Invasive Plants in the Eastern United States - USDA Forest Service
- Weeds Gone Wild: Alien Plant Invaders of Natural Areas - Plant Conservation Alliance
- Element Stewardship Abstract - The Nature Conservancy
- Fire Effects Information System - USDA Forest Service
- Know Your Knapweeds - North Dakota State University
- Weed of the Week - USDA Forest Service
- Weed Field Guide - USDA Forest Service
- Plant Invaders of Mid-Atlantic Natural Areas - National Park Service and U.S. Fish and Wildlife Service
Selected Images
Maps
EDDMapS Distribution - This map is incomplete and is based only on current site and county level reports made by experts, herbaria, and literature. For more information, visit www.eddmaps.org
State List - This map identifies those states that list this species on their invasive species list or law. For more information, visit Invasive.org
Invasive Listing Sources
- Alberta Weed Control Act
- Arizona Noxious Weeds
- California Invasive Plant Council
- California Noxious Weeds
- City of Ann Arbor Michigan Parks and Recreation
- Colorado Noxious Weeds
- Connecticut Invasive Plant List
- Connecticut Invasive Plant Working Group
- Connecticut Noxious Weeds
- Delaware Invasive Species Council
- Delaware Invasive Species Council Invasive Species List
- 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.
- Invasive Plant Association of Wisconsin
- Invasive Plant Species of West Virginia
- 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 - Significant Threat
- Maryland Cooperative Extension Service. 2003. Invasive Plant Control in Maryland. Home and Garden Information Center, Home and Garden Mimeo HG88. 4 pp.
- Maryland Invasive Species Council - Invasive Species of Concern in Maryland
- Massachusetts Noxious Weeds
- Massachusetts Prohibited Plant List
- Michigan Noxious Weeds
- Minnesota Noxious Weeds
- Missouri Noxious Weeds
- Missouri SRISP Species List
- Nebraska Noxious Weeds
- Nevada Noxious Weeds
- New Jersey Invasive Species Strike Team 2017 Invasive Species List
- New Mexico Noxious Weeds
- Nonnative Invasive Species in Southern Forest and Grassland Ecosystems
- North Dakota Noxious Weeds
- Ohio Invasive Species Council
- Ontario’s Invading Species Awareness Program Tracked Species List
- Oregon Noxious Weeds
- Pacific Northwest Exotic Pest Plant Council, 1998
- Plant Invaders of Mid-Atlantic Natural Areas
- South Carolina Exotic Pest Plant Council
- Tennessee Exotic Pest Plant Council
- Utah Noxious Weeds - Control
- Virginia Invasive Plant Species List
- Washington 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
- Wyoming Noxious Weeds
Taxonomic Rank
| Kingdom: Plantae |
| Phylum: Magnoliophyta |
| Class: Magnoliopsida |
| Subclass: Asteridae |
| Order: Asterales |
| Family: Asteraceae |
| Genus: Centaurea |
| Subject: Centaurea stoebe ssp. micranthos (Gugler) Hayek |
Synonyms and Other Names
Other Common Names:
bushy knapweed
Related Scientific Names:
Acosta maculosa auct. non (Lam.) Holub (Synonym)
Centaurea biebersteinii (Gugler) Hayek (Synonym)