Native. Annual. Propagates by seeds.
Time of bloom: May to July.
Seed-time: June to August.
Range: Pacific Coast.
An unpleasant, hairy weed, with sticky, bristly burs which make it a pest to California wool-growers. Stem erect, clothed with stiff white bristles, one to three feet high, with spreading branches. Leaves rather thick, lance-shaped to linear, entire, and thickly covered with fine, bristly hairs much shorter than those on the stem. Flowers in crowded, terminal, leafy-bracted racemes which lengthen as the succession of bloom approaches the summit; when developed, the racemes may be five to ten inches long, peduncled, and have usually matured seeds at the base before the latest buds are unfolded. Corolla orange-yellow, about a quarter-inch broad, its five lobes spread salver-form, and the tube enclosed for about half its length in a bristly calyx with very narrow, pointed lobes. The stiff bristles on the calyx enable it to cling to clothing and the coats of animals, particularly sheep, and the seeds which it encloses are largely so distributed. These are four incurved nutlets, keeled on the back, rough, wrinkled, and about a tenth of an inch long. (Fig. 233.)
Fig. 233.- Yellow Burweed (Amsinckia intermedia). X 1/4.
When grain is but a few inches high and the soil is moist, the weed-seedlings should be raked out of it with a weeding harrow. Badly infested meadows should be cleansed by a short rotation containing a well-tilled hoed crop.