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.
Carduus nutans L.
Musk Thistle
Identification
Musk Thistle
Carduus nutans L.
- Life cycle
- Biennial or winter annual
- Height
- Up to 7 ft
Musk thistle is a biennial or winter annual growing up to 7 feet tall. A rosette forms the first year, with a flowering, elongating stem the second year.
Leaves are dark green with a light midrib, hairless on both sides, with long, sharp spines. The stems are hairless.
Flowers are solitary, terminal, nodding heads, 1.5 to 3 inches across, deep rose to purple. It has a fleshy taproot that is hollow near the surface.
Reproduction is by seed only, 20,000 or more per plant. Seeds stay viable for at least 10 years.
Control
Controlling musk thistle
- Best timing
- Fall is the preferred time to spray. Metsulfuron applied in spring, from bolting to bud stage, prevents seed production.
- Mowing and pulling
- Mow repeatedly at the early bud stage, cutting below the terminal bud before stems elongate.
- Herbicide
- Aminopyralid (Milestone), clopyralid, picloram (Tordon), aminocyclopyrachlor (Method), dicamba or metsulfuron (Escort, Cimarron Max).
- Biological control
- The seed head weevil Rhinocyllus conicus can cut seed production by nearly 80 percent, but it takes five to 10 years to build up.
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
Russian Knapweed
Acroptilon repens L.
PerennialUp to 3 ft
Grayish clumps with lavender, thistle like flowers and very dark roots.
Saltcedar
Tamarix ramosissima Ledeb.
Shrub or small tree5 to 20 ft
A shrub with scale like leaves and pink to white flowers. Also called tamarisk.
Think You Found It?