Houndstongue
Cynoglossum officinale L.
Biennial1 to 4 ft
Burred seeds that cling to animals and clothing, and a plant that is toxic to cattle and horses.
Centaurea maculosa Lam.
Spotted Knapweed
Identification
Spotted Knapweed
Centaurea maculosa Lam.
- Life cycle
- Biennial or short lived perennial
- Height
- 1 to 3 ft
Spotted knapweed is a biennial or short lived perennial with a large taproot, 1 to 3 feet tall. The main stem leaves are pinnately divided. Flowering heads have stiff bracts tipped with a dark fringe, and the flowers are usually pinkish purple.
It was introduced from Eurasia as a contaminant in alfalfa and clover seed. It establishes quickly on disturbed ground and appears to inhibit the growth of surrounding vegetation.
Control
Controlling spotted knapweed
- Best timing
- Act as soon as plants are found. Follow up treatment is necessary, because many control attempts have failed without it.
- Mowing and pulling
- Pull visible plants by hand and destroy them by burning or mulching, then treat the area to stop seedlings. Treat 10 to 15 feet beyond the edge of a patch.
- Herbicide
- Aminopyralid (Milestone), picloram (Tordon) and dicamba.
- Biological control
- Hand removal and herbicide are the most cost effective options in North Dakota. Ask NDDA or NDSU about biological agents.
Always follow the product label, and check rates in the North Dakota Weed Control Guide from NDSU. Your county weed control officer can tell you what fits your land. Source: NDSU Extension W1411 (December 2025).
Keep Looking
Other weeds on the state list
Palmer Amaranth
Amaranthus palmeri S. Watson
Summer annual6 to 8 ft
A fast growing pigweed that has cut corn and soybean yields sharply.
Absinth Wormwood
Artemisia absinthium L.
PerennialUp to 4 ft
Silvery gray, finely cut leaves, small yellow flowers and a very distinctive smell.
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