3 species
3 subspecies and varieties
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Sonchus arvensisfield sow-thistle, perennial sow-thistle
Distribution: Introduced noxious weed, found across the United States and Canada.
Habitat: Usually in disturbed ground, dry to wet.
Origin: Introduced from Europe
Flowers: July - October
ssp. arvensis – field sow-thistle, corn sow thistle, perennial sow thistle
ssp. uliginosus – field sow-thistle, marsh sow thistle, wet ground sow thistle
Sonchus asperprickly sow thistle, spiny leaf sow thistle
Distribution: Cosmopolitan; common in the Pacific Northwest
Habitat: Disturbed areas, roadsides, gardens
Origin: Introduced from Europe
Flowers: July - October
Sonchus oleraceuscommon sow thistle
Distribution: Occurring on both sides of the Cascades crest in Washington, but more common on the west side; widely distributed throughout North America.
Habitat: Roadsides and waste ground.
Origin: Introduced from Europe
Flowers: July-October