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Statewide IPM Program, University of California

Sowthistles  (Sonchus spp.)

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Life stages of Sowthistles top picture bottom left picture bottom right picture

Sowthistles are among the most common weeds in farms and gardens in spring. They can be seen at any time of the year in mild climates, but commonly germinate from late fall to early spring with the highest numbers of mature plants present in spring and early summer. Flowers are yellow and mature into fluffy white seed heads. Annual sowthistle, S. oleraceus, is widespread in California. There are 5 Sonchus species common in California, two of which are considered invasive, spiny sowthistle, S. asper, and prickly sow thistle, S. asper ssp. asper.


The sowthistle seedling has markedly stalked, almost egg-shaped cotyledons (seed leaves), with rounded tips. Cotyledons often have a powdery coating, but later leaves have only a few hairs. Later leaves also have prickles or teeth along the edge with a winged stalk on the third or fourth and later true leaves.

Mature plant

Stems are hollow and release a milky sap when cut open.


Flowers are yellow and mature into fluffy white seed heads.


Reproduces by seed.

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