spotted knapweed

(Centaurea stoebe ssp. micranthos)

               
Conservation Status

IUCN Red List

not yet assessed

spotted knapweed

NatureServe

NNA - Not applicable

SNA - Not applicable

Minnesota

not listed

Weed Status

SN – State noxious weed

Invasive

Nativity

Native to Europe. Introduced and widely naturalized in North America

Occurrence

 

 
Habitat

Dry. Roadsides, railroads, abandoned fields, ditches, disturbed sites. Full sun.

 
Flowering

June to September

     
Flower Color

Pink to purple

     
Height

12 to 48

     

Identification

This is a 12 to 48 tall, erect, biennial or short-lived perennial forb that rises on 1 to 20 stems from a stout taproot.

In the first year it produces a rosette of basal leaves. In the second year it sends up 1 to 20 leafy flowering stems.

The stems are erect or ascending, somewhat 4-angled but not winged, and branched at or above the middle. They are whitish- or grayish-green and rough to the touch due to a sparse covering of minute, short, stiff hairs. When young, they are also covered with short, soft, matted, woolly hairs, but these disappear quickly.

Basal leaves are inversely lance-shaped to elliptic in outline, up to 6 long, and up to 2¾ wide. They whitish- or grayish-green and are usually deeply pinnately divided into 2 to 4 pairs of lobes. The outermost leaves of the rosette may be undivided or have a few teeth.

Stem leaves are alternate. Lower stem leaves are stalkless or on short stalks and similar to basal leaves. Middle and upper stem leaves are mostly stalkless. The leaf blade either does not or only slightly extends down the stem. Middle stem leaves are deeply pinnately divided into several pairs of linear lobes, the lobes often again divided. The leaves become much smaller and less divided as they ascend the stem. Uppermost leaves are mostly unlobed, especially within the inflorescence. The upper surface and lower surfaces are rough to the touch due to a sparse covering of minute, short, stiff hairs. The margins are untoothed.

The inflorescence is a single ¾ to 1 in diameter flower head at the end of the stem and each branch. At the base of the flower head is an egg-shaped, to ½ long, ¼ to 5 16 in diameter whorl of bracts (involucre). The bracts of the involucre are pressed closely together. They do not have sharp spines at the tip. They are green with dark brown to black tips and have a fringe of stiff, spreading or upward curved bristles. The bristles eventually turn black and have the appearance of eyelashes. The “eyelashes” are short, no more than half as long as the bract to which they are attached is wide.

There are numerous disk florets and no ray florets. The outermost disk florets are enlarged, sterile, and light purple to pinkish-purple. They may appear ray-like but closer examination shows them to be short tubes with 5 long lobes. The inner florets are white to pink and fertile.

The fruit is a brown or blackish-brown achene with a tuft of white, 1 32 to long bristles at the tip.

 
Similar
Species

Bachelor’s button (Centaurea cyanus) stem leaves are lance-shaped and unlobed. The leaf underside is woolly, even at maturity. It has blue to purple flowers. The tips of the involucral bracts are not dark, though the “eyelashes” are.


Distribution Distribution Map   Sources: 2, 3, 4, 5, 7, 22, 28.

Comments

 


Taxonomy

Family:

Asteraceae (aster)

 

Subfamily:

Carduoideae

 

Tribe:

Cynareae

 

Subtribe:

Centaureinae

 
Synonyms

Acosta maculosa

Centaurea biebersteinii

Centaurea maculosa

 
Common
Names

spotted knapweed


 

 

 

 

 

 

 

 

 

Glossary

achene

A dry, one-chambered, single-seeded fruit, formed from a single carpel, with the seed attached to the membranous outer layer (wall) only by the seed stalk; the wall, formed entirely from the wall of the superior ovary, does not split open at maturity, but relies on decay or predation to release the contents.

 

bract

Modified leaf at the base of a flower stalk or flower cluster.

 

involucre

A whorl of bracts beneath or surrounding a flower or flower cluster.

 

linear

Long, straight, and narrow, with more or less parallel sides, like a blade of grass.

       

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MinnesotaSeasons.com Photos

   

Plant

  spotted knapweed    
       

Inflorescence

  spotted knapweed   spotted knapweed
       

Flower Head

  spotted knapweed    
       
       

 

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Slideshows

   
  Centaurea maculosa
Matt Lavin
 
  Centaurea maculosa  
 
About

Introduced perennial with stems upwards of 1 m tall, the fringed-tipped involucral bracts (phyllaries) often have a dark patch (hence the common name), corolla usually rose-purple, rarely white, dry disturbed sites or on well-drained substrates (e.g., river and stream gravel) from low elevations to mountain meadows and mountain big sagebrush steppe.

 
     
  Spotted Knapweed (Centaurea maculosa)
Andree Reno Sanborn
 
  Spotted Knapweed (Centaurea maculosa)  
     
  Spotted Knapweed (Centaurea stoebe)
Bill Keim
 
  Spotted Knapweed (Centaurea stoebe)  
     
  Centaurea stoebe (Spotted Knapweed)
Allen Chartier
 
  Centaurea stoebe (Spotted Knapweed)  

 

slideshow

     

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Other Videos

 
  Spotted Knapweed, identification of the Wisconsin Invasive Species Centaurea stoebe
uwcoopextension
 
   
 
About

Uploaded on Jan 31, 2011

This is part of a series of videos providing key characteristics for the identification of invasive plants listed in Wisconsin's invasive species administrative rule NR 40. These videos are produced by Dr. Mark Renz of the University of Wisconsin-Madison. For more information on invasive plants and invasive plant management in Wisconsin visit http://fyi.uwex.edu/weedsci or http://ipcm.wisc.edu/Publications/WeedSciencepublications/tabid/116/Default.aspx

 
     
  Spotted Knapweed - Centaurea maculosa
adamitshelanu
 
   
 
About

Published on Jun 17, 2014

Spotted Knapweed - Centaurea maculosa

Uncle Steve examines this beautiful blossom "somewhere" in Randolph County, North Carolina: Spotted Knapweed

Centaurea maculosa

Date: 13 JUNE 2014

 
     
  LITTLE THINGS big problems-- Spotted Knapweed
Gr8LakesRestoration
 
   
 
About

Uploaded on Oct 3, 2011

The Apostle Islands National Lakeshore is a collection of isolated islands in Lake Superior. Its natural beauty brings thousands of people to kayak, bird watch, sight see, camp, fish, and hike. With these recreationist also comes the potential to introduce non native plants and animals to new places. One plant of major concern is spotted knapweed. It is a beautiful purple flower, but prevents other plants from growing nearby. It is moved accidently from one island to another by seeds stuck to people and their gear. The National Park Service works hard to control its spread, but needs your help. Keep your gear clean, especially when moving from one trail to another or from island to island.

 
     
  Spotted Knapweed ~ Invasive Species
Wandering Sole TV
 
   
 
About

Published on May 24, 2014

Spotted Knapweed (Centaurea maculosa), native to Eastern Europe, is an invasive species on the North American continent. It has infested around 40,000 hectares of land in British Columbia and there are fears this could spread to over one million hectares. Over 7 million acres (28,000 km^2) have been affected in the United States. While causing many problems, including soil erosion and the squeezing out of native species of plants, it does produce a lot of nectar and is a favourite with bees.

Lacking natural predators and diseases, invasive plant species grow and spread rapidly throughout native ecosystems. Once established, invasive plants are very difficult to control and they choke out native species. This greatly affects wildlife habitat and rangeland. On a global scale, invasive pant and animal species are considered to be the second largest contributor to the loss of biodiversity, next to the loss of habitat.

 
     
  Environmental Laboratory - U.S. Army Corps of Engineers
Environmental Laboratory USACE
 
   
 
About

Published on Feb 15, 2013

Centaurea biebersteinii - Spotted Knapweed

 
     

 

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