PERENNIAL SOWTHISTLE

(Sonchus arvensis)

COMMON NAMES:

Corn sow thistle, creeping sow thistle, field milk thistle, field sow thistle, and hare’s lettuce

DESCRIPTION:

Perennial sowthistle seed germinates when the soil has warmed up in the spring. The seeds are reddish brown, ridged and wrinkled with a tuft of fine white hairs. When the plant is broken, both the leaves and stem exude milky latex. All the plant parts are filled with a bitter, milky juice. The seedling grows slowly for about 2 weeks until the leaves are about 1 inch long and then it forms a rosette. The first year the rosettes form vertical roots up to 6.5 feet deep. The root system is extensive and composed of downward and horizontally growing roots that can be 5- 10 feet deep that can produce new plants from small root pieces. Root pieces that have been cut during cultivation can produce a flowering plant within a year. Bolting usually occurs in the second year when the rosette has 12-15 leaves. Alternate, lower leaves are deeply lobed, upper leaves clasp the stem; similar to a dandelion leaf except with teeth ending in small weak prickles. Flowers are bright yellow up to 2 inches wide daisies and bloom from June through August. Perennial sowthistle spreads vegetatively, as well as through wind-born seeds. A single plant can produce up to 9,750 seeds.

KEY FEATURES OF PERENNIAL SOWTHISTLE:

The deep yellow flowers look similar to dandelions. Below the flower heads, the stem will have yellow hairs. Leaves clasp the stem and alternate with spiny toothed margins.

HABITAT:

Perennial sowthistle like to be in croplands, meadows, right-of-ways, rangeland, edges of gardens, and ditch banks.

CONTROL:

There are herbicides and other control methods that commonly control perennial sowthistle. For more information on these herbicides and other control methods contact the SCWP office.

OTHER FACTS:

Perennial sowthistle is said to be a favorite for rabbits. In dry conditions is not favorable for Perennial sowthistle and is less of a problem in the dry years. Alfalfa and perennial grasses are strong competition for this plant.