Sonchus oleraceus (Common Sowthistle)
|Also known as:||Annual Sowthistle|
|Life cycle:||annual, biennial|
|Habitat:||sun; roadsides, disturbed sites, waste places, fields|
|Bloom season:||July - October|
|Plant height:||2 to 10 feet|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Tight clusters (corymbiform) of yellow dandelion type flowers, ¾ to 1¼ inch across, at the top of the stem and arising from leaf axils. Closed flower heads of bracts, receptacle and ray flowers (petals) is thick, barrel to vase shaped, sometimes finely hairy on the stalk below the cluster, and with several small attending leaves at the base of cluster.
Leaves are mostly deeply divided with triangular lobes, though upper leaves may be merely toothed or shallowly lobed. The lobe at the leaf tip is typically broadly spade shaped or triangular. Lower leaves are long stalked, up to 10 inches long and 2½ inches wide. Upper leaves are smaller and clasping, with angled lobes at the base of the leaf that extend past the stem. All leaves are coarsely toothed with small, soft prickles. Stems and leaf surfaces have a dull waxy sheen, stems crisp but brittle, very leafy,
Notes:Common Sowthistle has become widely cosmopolitan throughout the Americas and Asia due to human activity. A sporadic weed of cultivated gardens and disturbed areas, it does not encroach readily into high grade habitats and is likely under reported within Minnesota. It is distinguished from other sowthistles primarily by the triangular lobes on the leaves and the angled lobes at the leaf base. It is less prickly than Sonchus asper (Spiny Sowthistle) and has smaller flowers than Sonchus arvensis (Perennial Sowthistle).
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Photos courtesy Peter M. Dziuk, taken in a private vegetable garden in Anoka county.
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