Spotted Knapweed
Centaurea maculosa Lam.
Biennial or short lived perennial1 to 3 ft
Pinkish purple flowers with dark fringed bracts. Takes hold fast on disturbed ground.
Linaria vulgaris
Yellow Toadflax
Identification
Yellow Toadflax
Linaria vulgaris
- Life cycle
- Perennial
- Height
- 12 to 24 in
Yellow toadflax is a creeping perennial, 12 to 24 inches tall. Leaves are pale green, narrow, about 2.5 inches long and pointed at both ends.
Flowers are about an inch long with a bearded orange throat, similar to snapdragons or butter and eggs, which are common garden flowers.
It was introduced into the US as an ornamental in the mid 1800s. An extensive root system makes it an aggressive invader of rights of way, rangeland, waste places and cultivated fields. It is difficult to control once established.
Control
Controlling yellow toadflax
- Best timing
- In research, treatments from mid June through mid September reduced infestations for at least two years.
- Mowing and pulling
- Keep competitive forage at the right stocking rate. Burning is not effective.
- Herbicide
- No herbicide is labeled for yellow toadflax. Research found picloram (Tordon) with Overdrive worked. Check the North Dakota Weed Control Guide for rates.
- Biological control
- The weevil that works on Dalmatian toadflax failed on yellow toadflax in North Dakota. Other agents are still being tested.
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
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.
Palmer Amaranth
Amaranthus palmeri S. Watson
Summer annual6 to 8 ft
A fast growing pigweed that has cut corn and soybean yields sharply.
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