MARSH SOWTHISTLE - Sonchus arvensis L. ssp. uliginosus (Bieh.) Nyman

Asteraceae - (Sunflower family)

This perennial arising from an extensive creeping root system is commonly 1 to 6 feet tall, glabrous, at least below the inflorescence and often covered with a waxy film which can be rubbed off. Herbage has a milky juice. Leaves are prickly-margined, the lower and middle ones are usually pinnately lobed to pinnatifid, mostly 4 to 10 inches long and 1 to 1 1/2 inches wide. Upper leaves are progressively less lobed and become clasping, uppermost leaves bractlike. Flowering heads, 1 to 1 1/2 inches across at anthesis, grow in a terminal flat to a domelike cluster. It has yellow ray flowers, which are fertile. Achenes are flattened, ribbed and rugose, with pappus of capillary bristles.

Marsh sowthistle was introduced from Europe and is a creeping perennial. Marsh sowthistle (listed by various authors as S. uliginosus or S. glabrescens) lacks gland-tipped hairs.

(Courtesy of Weeds of the West)

Sowthistle can be treated with 2,4-D, Transline, Clarity, and Milestone with equal effectiveness. It is fairly competitive and can invade wet pastures and barrow ditches even which good grass cover. Fortunately it responds well to herbicide treatments.

NOTE: All Pesticide application recommendations are based on label directions and experience with these products in Fremont County Wyoming. However, labels change from time to time. Ultimately it is the responsibility of the applicator to insure the pesticide application is made within the directions on the current product label. If you are unsure of, or have questions concerning treatment method or a chemical usage please consult your local Weed & Pest office, or a licensed professional.