Coefficient of Conservatism:
Coefficient of Wetness:
R. W. Smith
Probably native originally in the Western Hemisphere and early spread from eastern North America to Europe and elsewhere. Disturbed places including dumps, vacant lots, farmyards, roadsides, and disturbed mudflats and shores (especially recently exposed ones). First collected in 1860 in Washtenaw Co.
A tall annual plant, with very long-lived seeds and appearing quite dramatically when appropriate disturbance or exposure causes long-dormant seeds to grow. The flowers may be white or purple; the name D. tatula L. was applied to the latter form, but as the difference has been shown to result from a single gene it is hardly worthy of recognition, except as f. tatula (L.) B. Boivin.