Distribution: Occurring east of the Cascades crest in Washington; Alaska to California, east to the Great Plains, also in eastern North America.
Habitat: Roadsides, fields, irrigation ditches, and other disturbed open areas where moist.
Origin: Introduced from Eurasia
Conservation Status: Not of concern
Annual herb with weak scrambling stems bearing minute backwards pointing prickles.
Simple, spoon-shaped, lightly hairy.
Small, blue to violet ,with 5 lobes at tip.
4 tiny nutlets.
The strongly toothed calyx that encloses the fruits like a clam shell is distinctive; look also for the small blue flowers and backward pointing prickles on the stems.