- the large and varied plant family Compositae (or Asteraceae), typified by herbaceous plants having alternate, opposite, or whorled leaves and a whorl of bracts surrounding the flower heads, which are usually composed of a disk containing tiny petalless flowers and a ray of petals extending from the flowers at the rim of the disk, some flower heads being composed only of a disk or a ray and some plants having clusters of flower heads, and including the aster, daisy, dandelion, goldenrod, marigold, ragweed, sunflower, thistle, and zinnia.
