Brassica juncea, Cosson
Time of bloom: May to July.
Seed-time: June to August.
Range: Ontario to Manitoba, southward to Georgia and Kansas.
Habitat: Grain fields, roadsides, and waste places.
Fig. 128. - Charlock (Brassica arven-sis). X1/4.
A special pest in grain fields, as its early season of bloom enables it to foul the ground with its seeds before the grain is ready to harvest and the smooth, glaucous foliage renders it impervious to injury from sprays that would not also kill the accompanying crop.
Stem one to four feet tall, erect, rather stout, with few branches. Lower leaves pinnatifid, with terminal lobe very large, coarsely toothed, and with long petioles; upper leaves oblong, nearly entire, tapering to the base, all light green, rather thick, smooth, and glaucous. Flowers bright yellow, more than a half-inch broad, clustered at the top of racemes, which, before the pods are all formed, often become more than a foot long. Siliques one to two inches long, nearly a third of their length taken by a slim, awl-shaped, empty beak. Seeds globular and brown. (Fig. 129.)
Harrow young seedlings from grain fields with a weeding harrow. Plants that survive the treatment should be hand-pulled while in early bloom. If seeds have matured and fallen, stubbles should be burned over for the purpose of destroying them. Plants of roadsides and waste places should also be pulled or cut before seed is formed.