ASTER, a large genus of plants of the family Compositae, so named from the radiate or star-like appearance of the flowers, and known as asters or star-worts (Gr. hQT,p, a star). There are some 400 species, found chiefly in North America but scattered sparsely in Asia, Europe and South America. They are usually perennial, leafy-stemmed herbs, sometimes somewhat woody at the base, and bearing in late summer and autumn a profusion of flowering heads, mostly in clusters, but sometimes solitary. In each head numerous showy blue, red, purple or white rays sur round a central disc of minute yellow tubular flowers. Many asters are strikingly handsome, and various species are cultivated as ornamental plants, flowering throughout the autumn and sometimes even until December. The flowers recall those of the daisy, and one variety is known in England as the Michaelmas daisy. The only species (A. Tripolium) native to Great Britain, grows abundantly in saline marshes r ar the sea.
In North America there are upwards of 25o species, most numerous in the northeastern United States and adjacent Canada, with about 75 species, some 45 of which are native to the State of New York. They are generously represented in the Rocky Moun tain region, some 5o species being found in Utah and Nevada, and about 20 occur in California. In the region east of Manitoba and Kansas and north of Tennessee, the asters, together with the goldenrods, dominate the floral landscape in autumn, filling fields, woodlands and roadsides with masses of brilliant colour. Among the many conspicuous kinds the New England aster (A. novae angliae), found abundantly from Quebec to Alberta and south to South Carolina and Colorado, is the best known. It grows 3 ft. to 5 ft. high with handsome purple flowers 1 in. to 2 in. across. Other noteworthy species are the New York aster (A. novi-belgii) and the smooth blue aster (A. laevis), both of which, like the fore going, are widely cultivated. In California the common aster is A. chilensis; other noteworthy species are the somewhat woody desert aster (A. tortifolius) and the reed-like spiny aster (A. spinosus), which grows 9 f t. high in the Colorado desert and is popularly called Mexican devil-weed.
The China aster (Callistephus chinensis) is also a member of the family Compositae. It is a hardy annual, a native of China, which by cultivation has yielded a great variety of forms.