Perennial sowthistle

Sonchus arvensis L.

Life cycle

Erect, patch-forming perennial.

Perennial Sowthistle Rosette
Perennial sowthistle plant.

Leaves

Seedling leaves initially develop from a basal rosette from a deep taproot. Lower leaves are alternate, bluegreen, 4 to 12 inches long with two to five lobes with prickly teeth on each side, gradually becoming smaller towards the top with a clasping base. Leaves have a thickened midvein and exude a milky sap when damaged. Leaf midvein is not prickly underneath.

Perennial Sowthistle Lower Leaf Perennial Sowthistle milky sap
Lower leaf of perennial sowthistle (left). Milky sap of perennial sowthistle (right).

Stems

Erect, herbaceous stem up to 5 feet tall that branches only near the flowers. Stems are hollow and smooth with ridges and exude a milky sap when damaged. Upper stems may have gland-tipped hairs.

Perennial Sowthistle Upper Leaf
Clasping leaf base of perennial sowthistle. 

Flowers and fruit

Bright yellow ray flowers are 1 to 2 inches wide and found in clustered heads. The seed is enclosed in a single-seeded, narrow, oval, reddish brown, ribbed, wind-disseminated fruit.

Perennial Sowthistle Flower
Perennial sowthistle flower.

Reproduction

Seeds and extensive creeping roots.

Similar weeds

Annual sowthistle (S. oleraceus L.) Differs by having an annual life cycle and short taproot, less prickly leaf margins, and pale yellow, 0.5- to 1-inch-wide flower heads. Leaf midvein is not prickly underneath.

Prickly lettuce (Lactuca serriola L.) Differs by having an annual or biennial life cycle; fine prickles on leaf margins and sharp prickles on the underside of the leaf midvein; and a many branched, spreading panicle with numerous, pale yellow flower heads less than 0.5 inch wide.

Prickly lettuce leaf midvein
Sharp prickles on the underside of the leaf midvein of prickly lettuce.

Spiny sowthistle [S. asper (L.) Hill] Differs by having an annual life cycle and short taproot, leaf margins with many sharp prickles, earlike lobes where the leaf attaches to the stem, and flower heads 0.5 to 1 inch wide. Leaf midvein is not prickly underneath.

spiny sowthistle leaf
Spiny sowthistle leaf.

Print a PDF of this page: Perennial sowthistle.

Back to Identifying weeds in Christmas trees.

The MSU IPM Program maintains this site as an access point to pest management information at MSU. The IPM Program is administered within the Department of Entomology, fueled by research from the AgBioResearch, delivered to citizens through MSU Extension, and proud to be a part of Project GREEEN.