Time of bloom: June to July.
Seed-time: First seed ripe in July. Plants dry and ready for tumbling in September. Range: All states of the Middle West as far south as Missouri and
Fig. 135. - Hedge Mustard (Sisymbrium officinale). X 1/3.
Kansas, northwestward to Washington; all the Canadian provinces from Quebec to Vancouver Island. Habitat: Grain fields and grasslands, waste places.
A native of Central Europe brought to this country in impure commercial seeds; by this agency it still travels, and no doubt journeys farther in this way than when wind-driven about the country.
Stem two to four feet high, slender, smooth, and exceedingly branched and bushy. Leaves deeply pinnatifid, the segments nearly linear, toothed or entire, the upper ones reduced to thread-like thinness; when the plant is young the lower leaves are downy and the basal ones lie on the ground in rosette form, but these wither away and the later leaves are smooth. Flowers pale yellow, about a third of an inch across, on elongating racemes that leave behind alternating rows of stiff, diverging, needle-like pods, two to four inches long but hardly thicker than their short pedicels. Each pod usually contains more than a hundred seeds - the fecundity of the weed is almost incredible. When mature the stems become very brittle, breaking away at the surface of the ground, and the plants are afterward the sport of the winds; on the prairies they often roll for miles, but in fenced and uneven ground they are battered to and fro, seeding the soil the more thickly for such restriction. (Fig. 136.)
Sow clean seed. Harrow seedlings out of grain fields in the spring. Harvest infested meadows before the first seeds ripen. Burn over stubbles for the purpose of killing the seeds on the ground. The plant gives no trouble in cultivated ground, for there the stroke of a hoe destroys it when young. The smooth foliage is unharmed by sprays.
Fig. 136. - Tumbling Mustard (.Sisymbrium altissimum). X 1/4.