spotted knapweed
(Centaurea stoebe)
This species is Introduced in the United States
Appearance
Centaurea stoebe is a bushy, winter-hardy, upright perennial forb living 3 - 5 years or sometimes longer, with a deep taproot.
Foliage
Rosette leaves bluish-green, hairy, and covered with shiny specks interspersed with translucent dots, 4-8 in. (10-20 cm) long. The size of the leaves decreases in size above the middle of the stem. They are alternate, spiraling, and jutting out and upward. Basal leaves deeply divided into elliptic or linear lobes. Lobes become more slender and fewer on upper leaves.
Flowers
Flowers from June-November. Each branch topped by an egg-shaped flower bud covered with overlapping rows of dry, fringed green bracts with black tips. Bracts eventually part at the top to allow a constricted pinkish-to-lavender thistle plume to radiate out and up, 0.75-1 in. (2-2.5 cm) wide and overall about 1 in. (2.5 cm) long.
Fruit
Fruits appear from June-February. Tightly packed seed heads of oblong, brownish, hairy nutlets (achenes), 0.1 in. (3 mm) long, topped by short stubby bristles. A thousand seeds can be produced per plant.
Ecological Threat
Centaurea stoebe rapidly colonizes roadsides and disturbed lands, especially dry sites. It can invade adjacent undisturbed prairies and open forests. A severe invasive species spreading into the South by seeds equipped for dispersal by wind, water, livestock, wildlife, and human activity, with viability in the soil for many years.
Citation
Winston, R.L., C.B. Randall, De Clerck-Floate, R., McClay, A., Andreas, J. and M. Schwarzländer. 2016. Field Guide for the Biological Control of Weeds in the Northwest. USDA Forest Service, Forest Health Technology Enterprise Team, Morgantown, West Virginia. FHTET-2014-08. Retrieved from https://bugwoodcloud.org/resource/pdf/Field_Guides_Series/Weeds_of_the_Northwest.pdf
Winston, R.L., C.B. Randall, B. Blossey, P.W. Tipping, E.C. Lake, and J. Hough-Goldstein. 2017. Field Guide for the Biological Control of Weeds in Eastern North America. USDA Forest Service, Forest Health Technology Enterprise Team, Morgantown, West Virginia. FHTET-2016-04. Retrieved from http://bugwoodcloud.org/resource/pdf/FHTET-2016-04_Biocontrol_Field_Guide.pdf
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 Lists - This map identifies those states that have this species on their invasive species list or law.
Invasive Listing Sources
- Indiana Invasive Species Council - Invasive Plant List
- Indiana Terrestrial Plant Rule
- Iowa Forest Invasive Plants
- Maryland Department of Natural Resources Policy: Restriction on Planting Exotic Invasive Plants
- Massachusetts Invasive Plants Advisory Group List
- Missouri Noxious Weeds
- Montana Noxious Weeds
- National Park Service, Mid-Atlantic Exotic Plant Management Team Invasive Plant List
- New Hampshire Prohibited Invasive Species
- New York Regulated and Prohibited Invasive Species - Prohibited
- Pacific Northwest Exotic Pest Plant Council, 1998
- Pennsylvania Department of Conservation and Natural Resources Invasive Plants
- Rhode Island Natural History Survey
Taxonomic Rank
| Domain: Eukarya |
| Kingdom: Plantae |
| Phylum: Magnoliophyta |
| Class: Magnoliopsida |
| Superorder: Asteranae |
| Order: Asterales |
| Family: Asteraceae |
| Subfamily: Carduoideae |
| Tribe: Cardueae |
| Genus: Centaurea |
| Centaurea stoebe |
References
Common Name Reference: USDA, NRCS. 2010. The PLANTS Database. National Plant Data Center, Baton Rouge, LA, USA.
Scientific Name Reference: USDA, NRCS. 2010. The PLANTS Database. National Plant Data Center, Baton Rouge, LA, USA.