FIELD PENNYCRESS, Thlaspi
arvense L. 1, seed; 2, seed pod; 3, upper part
of plant; 4, lower part of plant. Annual or winter
annual, reproducing by seed. Stems erect, 4 to 20 inches
(10 to 50 cm) tall, simple or sometimes branched above, smooth throughout.
Leaves alternate, simple, toothed, 1/2 to 2 inches (1.3 to 5 cm)
long, clasping stem with earlike projections. Flowers white with
4 petals, in racemes which lengthen greatly at maturity. Seed pod
flat, circular, about 1/2 inch (1.3 cm) in diameter, 2 valved, broadly
winged, with a deep, blunt notch at the top. Each pod contains several
seeds. Seed dark reddish-brown to black, ovate in outline, flattened,
about 1/16 inch (1.5 mm) long with about 10 curved, granular ridges on
each side. Found in small grains, legumes, and noncultivated areas.
This weed imparts a bitter, garlicky flavor and odor to milk.