This species is infrequent but locally common along roadsides and railroads in the southern and western counties, becoming rare or absent in the northeastern counties. It prefers a moist, sandy soil and, from its abundance in the prairies of our western counties, I believe it is essentially a prairie plant. Almost all of my plants are from roadsides, railroads, and fallow fields, and only a few grew along creeks and in open woodland where the seed could have come from roadsides. I believe this plant has been introduced throughout the state except in a few of our western counties where there are prairie habitats. The preceding statement is based upon the fact that complete stands of this species may be found in suitable habitats along roadsides where the ground has been made bare recently. The dense stands show the viability of the seed and that the most important factor in reproduction is bare, sandy soil.

[Specimens with long spreading hairs on the stem, pedicels, and pods have been called variety robusta]. One of my specimens [of var. robusta] was found along a low roadside in Spencer County and another in a fallow field along Otter Creek in Warrick County. Probably native. Paul Weatherwax collected it in Greene County along the Illinois Central Railroad near Bloomfield.