Time of bloom: Late June to July.
Seed-time: July to August.
Range: Ontario and Manitoba, Minnesota and the Dakotas.
Habitat: Grain fields and waste places.
Root-leaves tufted, forming a graceful rosette, deeply pinnatifid, the segments again cut and toothed, peti-oled, deep green, slightly glandular, hairy. Stem leaves also all pinnatifid, but smaller, more finely divided, and with short petioles. Stem two to four feet tall, erect, branching, and finely hairy. Flowers bright yellow, about an eighth of an inch broad, in elongated racemes; pods smooth, narrow, slightly curved, a little more than a half-inch long, on slender, spreading pedicels. Seeds very small, reddish brown, minutely roughened, very mucilaginous when wet, which is an aid to their distribution. (Fig. 137.)
Another nearly related plant with nearly the same range is the Gray Tansy Mustard (S. incisum, var. Hartwegianum, Watson), differing in that its much divided foliage is densely covered with soft, gray, appressed hairs. The Gray Tansy Mustard is later in flowering and in seed development, the pods being but a quarter-inch long, held nearly erect on short, ascending pedicels, making the racemes very slender.
Fig. 137. - Green Tansy Mustard (Sisymbrium incisum, var. filipes). X 1/4.
Harrow autumn rosettes from the crop in the spring, when the grain is but a few inches tall. Spray the young flowering stalks with Iron sulfate or Copper sulfate at the appearance of the first yellow blossoms. Destroy waste-land plants by deep cutting or hand-pulling.