Distribution: Introduced in much of the northern part of the United States; common east of the Cascades in Washington and Oregon
Habitat: A weed of moist soil in fields, roadsides and other disturbed areas, mostly east of the Cascades.
Flowers: May - July
Origin: Introduced from Europe
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.