The Genus Aster

Remark The words or terms in red (actually dark orange) in the text are defined in a glossary.

aug_08_11.gthmb can't be loaded. In Greek αστηρ (aster) means star, and the name refers then to the shape of the flower head.

Asters are usually characterized by leafy stems, and opposite, often spear-shaped (lanceolate) leaves, ranging from one to three inches in length. The small flowers are daisy-like, with yellow or orange centers that turn reddish-brown after they are fertilized and fine, often thickly growing petals. The stems are frequently much branched near the top, producing large clusters of flowers which individually range from less than one inch, to two inches across. The colors range from deep purple through lavender, blue, pink and rose to white. Most species species bloom in the late summer and fall when many other plants have finished blooming.

With 150 species in North America, 55 of which grow in the northeast, the Aster genus is arguably the largest on the continent. To further confuse botanists, asters easily hybridize. Small, white asters are especially confusing.

Traditional treatments place most asters in the genus Aster Linnaeus. However, during the last decade analyses of morphology, chloroplast DNA restriction fragment length polymorphisms and ITS sequence data, and on going karyotype studies have all demonstrated that asters are polyphyletic and members of a number of very distinct phylads within the tribe. Asters can be divided into two categories following the general phylogeny of the entire tribe:

The genus Aster is then now generally restricted to the Old World species, with Aster amellus being the type species of the genus (and of the family Asteraceae). The other species have now been reclassified in the genera Almutaster, Canadanthus, Doellingeria, Eucephalus, Eurybia, Ionactis, Oclemena, Oligoneuron, Oreostemma, Sericocarpus and Symphyotrichum.

In what follows, we will then use in the list below the new taxonomy, with the old in parenthesis.

According to the Flore Laurentienne by Frère Marie-Victorin, the following species can be found in Québec: