Sonchus oleraceus (Common Sowthistle)

Plant Info
Also known as: Annual Sowthistle
Genus:Sonchus
Family:Asteraceae (Aster)
Life cycle:annual, biennial
Origin:Europe
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):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: 7+petals Cluster type: panicle

[photo of flowers] 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: Leaf attachment: alternate Leaf type: lobed Leaf type: simple

[photo of leaves] 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,

Fruit:

[photo of fruit] Fruit is a dark brown seed, slightly flattened and somewhat spindle shaped, with textured, wrinkly ribs and a tuft of bright white hairs to carry it off in the wind.

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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More photos

Photos courtesy Peter M. Dziuk, taken in a private vegetable garden in Anoka county.

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