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ASTER
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Asters, genus Aster, are any of several large PLANTS, commonly called asters, starworts, Michaelmas daisies, or frost flowers. The genus, which belongs to the composite, or sunflower, family, Compositae, includes approximately 250 to 500 species. Asters are found chiefly in North America, with some species extending into South America; others are distributed throughout Europe and Asia. Asters reach their greatest complexity in the northeastern United States and adjacent Canada, where more than 65 species are found.
The asters are mostly coarse-growing, leafy-stemmed plants that are occasionally somewhat woody at the base. Although most are perennials, a few are annuals and biennials. All have alternate, simple leaves that are untoothed or toothed but rarely lobed. In late summer and autumn the asters produce large clusters of flowering heads, although a few species have single heads. Each head contains a central disk of small yellow (sometimes orange, purple, or white), tubular flowers surrounded by numerous showy, ray flowers ranging from blue or violet shades of purple, to red, pink, or white. The ray flowers are never yellow. The tubular flowers are bisexual, having both a pistil and stamens; the ray flowers usually are sterile.
The asters are a striking, common component of the flora of late summer and fall. They grow profusely along roadsides and in vacant lots, as well as in prairies and forests. Common forest species of the eastern United States are the arrow-leaved aster, Aster sagittifolius; blue wood aster, A. cordifolius; and Short's aster, A. shortii. Well-known species of open areas include the hairy aster, A. pilosus; New England aster, A. novae-angliae; and heath aster, A. ericoides. Other species such as the spiny aster, A. spinosus, grow in desert areas. The asters are excellent garden ornamentals, and many species, hybrids, and cultivars (horticultural varieties) are grown.
The China aster, Callistephus cinensis, also a Compositae, is related to the true asters. Native to China, it is a handsome annual herb often grown for its late-summer blooms. Its showy, flowering heads grow to 13 cm (5 in) across.
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