CHARLOCK

(Brassica kaber, or Sinapis arvensis), early-flowering weed of the mustard family (Brassicaceae), widespread in grainfields in Europe and North America. Charlock reaches 1 m (3 feet) and has stiff bristles on the stems and leaves. The long pod fruits that form below the yellow flowers each enclose 10 to 12 black seeds. The closely related white mustard (B. hirta) has vanilla-fragrant, yellow flowers from which develop three to six large, yellow-seeded, bristly pods, swollen around the seeds. The seeds of both species contain a clear oil that is poisonous to livestock. White mustard seeds are a source of the condiment known as mustard (q.v.).