Carduus acanthoides L.
Plumeless thistle is a native of Eurasia with a wide variety of growth potential—it can be an annual or biennial from 1-6 feet tall. The stems have spiny ridges running up to the flower. The flowers are bright pink and relatively small.
Plumeless thistle reproduces mainly by wind seed dispersal. Because the plant is generally a biennial, it produces a rosette the first year followed by a flowering plant capable of producing many viable seeds the second year. Plumeless thistle closely resembles musk thistle; however, the flowers are smaller and don’t nod, and the leaves are more deeply serrated with hairy undersides. Timing, as with other biennials, is very important in control. Plumeless thistle is best controlled as a rosette or at the bolt stage of second-year plants. Once this plant has had time to successfully produce viable seed, it is too late for herbicide application and should be mechanically removed.
Currently, there are very few infestations found in Teton County. However, we do know that this weed species is found in Wyoming and neighboring states. Although this particular thistle is only moderately invasive, Teton County Weed and Pest classifies it as a top priority due to the likeliness of eradication.
If you find this weed on your property or around Teton County, please report it immediately at 733-8419