The CSU Extension in Gilpin County helps mountain residents improve their quality of life by offering a website, classes and programs that provide unbiased, research-based information on forestry, wildfire, wildlife, mountain gardening, noxious weeds and many other issues. Through our 4-H programs, we help youth develop life skills and to become more interested in Science, Technology, Engineering and Math (STEM) learning.
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Yellow toadflax (Linaria vulgaris)

Yellow ToadflaxState law: Toadflax must be eradicated or contained in Gilpin County.

Quick facts:

  • Perennial with stems that grow from one to three feet tall and narrow, linear leaves pointed at both ends.
  • A mature plant can produce up to 30,000 seeds annually a single stem has been reported to contain over 5,000 seeds. KEEP this plant from going to seed!
  • Seeds can remain dormant in the soil for up to ten years. In Gilpin County, the plant usually goes to seed in mid-late August.
  • Yellow toadflax can reproduce both by seeds and vegetatively. It can aggressively form colonies through adventitious buds from creeping root systems.
  • It is somewhat poisonous to livestock.

yellow toadflax rhizomeThe optimal time for herbicide application is during the flowering stage, this is when carbohydrate reserves in the root of the plants are at their lowest. Herbicides that have been somewhat effective on yellow toadflax control are picloram (Tordon 22K*), glyphosate (Roundup**), dicamba (Banvel), and chlorsulfuron (Telar DF). Repeat applications are necessary to achieve control.

Hand-pulling yellow toadflax may be effective for small infestations. This should be done before seed-set and repeated as long as there are viable seeds in the soil (up to ten years).

Caution: there is a native plant, Golden Banner (Thermopsis divaricarpa) which people sometimes confuse with toadflax. If you look at the leaves, it is impossible to mistake them.

The leaves of yellow toadflax are linear. The leaves of Golden Banner have three leaflets (like a clover).

 

Golden banner Golden banner (good/native) has leaflets like a clover
Yellow toadflax (Linaria vulgaris) Yellow toadflax (bad/noxious)has linear leaves

Additional information on yellow toadflax:

http://extension.colostate.edu/topic-areas/natural-resources/biology-and-management-of-the-toadflaxes-3-114/

www.co.silverbow.mt.us/documentcenter/view/106

http://adams.colostate.edu/ag/yellowtoadflax.htm