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Sowthistles (Sonchus spp.)
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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.
Seedling
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
Flowers are yellow and mature into fluffy white seed heads.
Reproduction
Reproduces by seed.
Related or similar plants
- Annual sowthistle, Sonchus oleraceus
- Spiny sowthistle, Sonchus asper
More information
- Broadleaf ID illustration
- Calflora's distribution map
- For agriculture: UC IPM Pest Management Guidelines
