Symphyotrichum spp.; aster [Asteraceae]  Large and highly variable group of blue, purple, red or white flowered annual, biennial, and perennial herbs.  Two dozen or more species are found in Wisconsin, plus many varieties and hybrids.  Heads often in much-branched clusters with both ray and disk flowers often the same color, subtended by two or more rows of bracts.  Many of our native asters grow in woodland understories or edges.  Most flower in late summer and fall.  [136]