TANSY MUSTARD, Descurainia
pinnata (Wait.) Britt. 1, stem; 2, upper portion of
flowering plant; 3, young plant; 4, lower stem and roots;
5, seed; 6, seed pod; 7, flower. Annual or
biennial, reproducing by seeds. Stems erect, slightly hairy,
1 to 3 feet (30 to 90 cm) high, much branched above. Leaves light
green, alternate, 2 to 4 inches (5 to10 cm) long, finely divided, almost
fernlike. Flowers small, pale yellow, produced on elongated racemes.
Seed pods narrow, smooth, slightly curved, 1/2 to 3/4 inch
(1.3 to 1.9 cm) long, 2-celled, many-seeded. Seeds small, oblong
to 3-angled with a groove on one side, dull red or light brown. Found
in cultivated fields, pastures, meadows, waste places, and roadsides. The
plant can produce a rank growth, crowding out grain and reducing crop yields.
A similar species, flixweed (Descurainia sophia), is also
found in abundance in much of the same area.