Leafy Spurge
Euphorbia esula L.
PerennialUp to 3 ft
Milky sap, narrow leaves and deep, spreading roots.
Centaurea diffusa Lam.
Diffuse Knapweed
Identification
Diffuse Knapweed
Centaurea diffusa Lam.
- Life cycle
- Annual or biennial
- Height
- Up to 2 ft
Diffuse knapweed is an annual or biennial up to 2 feet tall. A rosette forms the first year, with a flowering, elongating stalk the second year.
Leaves are grayish green and alternate. Basal leaves are whorled, and upper leaves are reduced and covered with fine hair. A single, erect, hairy stem grows from a taproot and is branched near the base.
Flowers are solitary, mostly white with a few pink or lavender. Seed head bracts end as sharp, rigid spines. Seeds are oblong, dark brown or gray, with lengthwise lines.
Control
Controlling diffuse 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
Musk Thistle
Carduus nutans L.
Biennial or winter annualUp to 7 ft
Nodding rose to purple flower heads. One plant can make 20,000 or more seeds.
Purple Loosestrife
Lythrum salicaria L.
PerennialUp to 8 ft
Rose purple flower spikes on wet ground, thick enough to slow water in ditches and canals.
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