Centaurea biebersteinii (Spotted Knapweed): purple Minnesota wildflowers

Centaurea biebersteinii (Spotted Knapweed)

Plant Info
Also known as:
Genus:	Centaurea
Family:	Asteraceae (Aster)
Life cycle:	biennial, short-lived perenn
Origin:	Europe
Status:	Noxious Weed
Habitat:	sun; dry fields, roadsides, waste areas
Bloom season:	summer, fall
Plant height:	2 to 3 feet
USDA PLANTS database:	Minnesota county distribution map
Spotted in Ramsey County at:	Battle Creek Regional Park Long Lake Regional Park Rice Creek Trail Corridor Vadnais/Snail Lake Regional Park

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Detailed Information

Flower:: Pink to purple, occasionally white, thistle-like flower heads 1 inch across at the end of branching stems. Each head is made up of many tubular flowers with 5 narrow lobes that fan out.
The bracts under the flower head also resemble those of a thistle and are green or brown tipped with brownish black, with coarse hairs all around the edge of the tip. A mature plant has 25 to 100 flower heads.
Leaves and stem:: Grayish blue-green, somewhat hairy leaves are deeply lobed into narrow segments. Near the base of the plant leaves may be up to 8 inches long and 2 inches wide, becoming progressively smaller as they ascend the stem. Leaves near the flowers are typically small, narrow and unlobed. The main stem is ridged and roughly hairy. One plant has up to 15 stems, each heavily branched.
Notes:: The stems and bracts are stiff and scratchy, making walking through a patch of this an uncomfortable experience. Spotted Knapweed is on the noxious weed list for Minnesota. It contains chemicals that poison the soil and inhibit native plants. The hundreds of seeds produced by one plant mostly stay within a few feet of the parent plant, thus it tends to form large, monoculture colonies. The first year it sprouts there is just a rosette of leaves, with flowers appearing the second year. Spotted Knapweed is one of 3 targeted plant species in Minnesota with an active bio-control program. The other 2 species are leafy spurge and purple loosestrife.

More photos

Photos taken at Long Lake Regional Park, New Brighton, MN, Rice Creek Trail Corridor, Shoreview, MN, Vadnais/Snail Lake Regional Park, Shoreview, MN July 2007 and 2008, August-September 2009

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Jess in Duluth
on: 2009-06-22 17:47:30

Found this beautiful flower along the hiking/ski trail at Chester Bowl Park in Duluth MN. Flowering on June 22nd.

Posted by: K Chayka
on: 2009-06-22 18:58:05

Beauty is in the eye of the beholder, I think. :) I loathe this plant, myself. It is weedy and invasive and has started taking over the prairie at my favorite park. I look forward to the day when they get a bio agent in there to wipe it out.

Posted by: JB in Randall, Morrison County
on: 2010-07-09 15:49:41

Why is it suggested in the bio-control program to use gloves to hand pull this? Is it poisonous to touch? I pulled some to ID it today and now I'm worrying... We don't have too much, it's just starting to bloom and I plan to hand pull it.

Posted by: JB in Randall, Morrison County
on: 2010-07-09 15:54:16

Nevermind, they must recommend gloves because of the scratchy stems. :) Thanks!

Posted by: K. Chayka
on: 2010-07-09 20:14:51

JB, besides the scratchy stems, I think some people may have a reaction (rash?) to the chemicals in the plant.

Posted by: Anna in Brown County
on: 2010-07-20 10:50:19

We located a thriving population of Spotted Knapweed on 270th avenue in Brown County along the abandoned portion of the road that dips down into the creek valley. (map)

Beautiful Flower. Too bad it's so invasive.

Posted by: Tom in Grand Marais
on: 2010-08-05 23:44:02

I found this plant growing at the edge of our gravel driveway. I agree that the flowers are beautiful--too bad it's a noxious weed! I haven't noticed them before in this area, so I'm wondering where it came from.