Native. Annual or winter annual. Propagates by seeds. Time of bloom: May to November. Seed-time: June to December.
A special pest of grass and clover fields, the earlier flowers maturing and dropping seeds into the soil before the accompanying crop is ready to harvest, thus assuring a continuity of its unwelcome presence. Seed-bearing plants are transported in baled hay and the seeds are a common impurity of grass seeds.
Stem two to five feet tall, erect, stiff, somewhat ridged, sparsely covered with spreading hairs, much branched at the top. Leaves thin, coarsely and sharply toothed, the lower ones long-ovate, tapering into margined petioles, the upper ones lance-shaped, acute, toothed only along the sides, sessile or with very short petioles, those on the branches still smaller and usually entire. Heads very numerous, in many corymbose clusters, on short pedicels, about a half-inch broad, the many narrow rays white or faintly tinged with purple; bracts of the involucre bristly-hairy and nearly linear. Achenes very small, light-colored, flattened, slightly hairy. Pappus double, the inner row of fine bristly hairs, the outer row of short slender scales. (Fig. 304.)
If the infestation is new and the weed not so abundant as to make the task impracticable, it will pay to hand-pull and remove the plants at the appearance of its first bloom, rather than that the ground should be fouled for as long as it is kept in clover or grass. Sheep prefer White-top to good hay. After the crop is harvested, turn in the flock and they will graze down the tufts of winter crown-leaves. Fields rankly infested are best treated by plowing under for winter wheat or a cultivated crop, to be followed by a clean reseeding.
Fig. 304. - White-top (Erigeron an-nuus). X 1/6.