Composite Flowers

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Composite Flowers, common name for one of the largest families of flowering plants, with more than 20,000 species. The common name refers to the clustering of the flowers into compact heads so that an entire cluster resembles a single flower, as in the familiar aster or dandelion.

The composite family is worldwide in distribution except for Antarctica, where two species of grasses are the only flowering plants known. Composites are particularly well adapted to semiarid parts of tropical and subtropical regions, to arctic and alpine tundra, and to temperate regions. They are poorly represented only in tropical rain forests.

Although the composite family contains nearly 10 percent of all the flowering plants, its direct economic importance is relatively small. Lettuce is the most important crop; other notable food plants are artichoke, endive, salsify, chicory, and tarragon. Sunflower and safflower are important sources of vegetable oils, and some members such as guayule have been studied as potential sources of rubber. Weedy members of the family include dandelion, thistle, cocklebur, and ragweed, which is a major source of the airborne pollen that affects hay fever sufferers. Horticulturally important members of the composite family include marigold, dahlia, zinnia, daisy, cosmos, chrysanthemum, tansy, and aster.

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