The common Michaelmas daisy is a tall (60–130 cm) herb of hybrid origin. Its inflorescence is a dense, single flower-like capitula. One plant has several capitulae, positioned at the top of the shoot in a panicle-like corymbose group. The capitula have two kinds of flowers: ray-florets, which are usually white or white–lightish purple, and disk florets, which are yellow and tubular. The common Michaelmas daisy flowers late in August-October.

The common Michaelmas daisy mainly spreads vegetatively in Finland, as the majority of its seeds are probably not viable. However, a wide variety of common Michaelmas daisy hybrids are used as ornamental plants, some of which may produce seeds that are able to germinate.The Common Michaelmas daisy has become established on eutrophic shores and the sides of ditches in particular, where it forms extensive stands in wet coastal meadows in the flood zone. It also grows in a wide range of ruderal habitats, including roadsides, wasteland, landfills and old yards and gardens, but in such locations the stands are small and probably short-lived. The common Michaelmas daisy can even spread to new habitats from small root fragments, which easily travel over long distances in flowing water.

Symphyotrichum salignum