Symphyotrichum laeve

Symphyotrichum laeve (formerly Aster laevis) is a flowering plant native to Canada, the United States, and Coahuila (Mexico). It has the common names of smooth blue aster, smooth aster, smooth-leaved aster, glaucous Michaelmas-daisy and glaucous aster.

Description
Smooth aster is 20 to 70 cm tall. Its leaves are arranged alternately on the stems, and their shape varies among lanceolate, oblong-ovate, oblong-obovate, and ovate. They measure from 3 to 20 cm long and from 1 to 2.5 cm wide. They are usually hairless, and the leaf edges are entire or bluntly or sharply toothed (crenate or serrate), sometimes with smaller teeth (serrulate).

Taxonomy
There are four varieties: Symphyotrichum laeve var. laeve, S. laeve var. geyeri (Geyer's aster), S. laeve var. concinnum, and S. laeve var. purpuratum.

Hybrids with this species and others of the genus have been reported, including three named as follows:
 * Symphyotrichum × gravesii between S. laeve var. laeve and S. dumosum;
 * Symphyotrichum × versicolor between S. laeve var. laeve and S. novi-belgii var. novi-belgii; and,
 * Symphyotrichum × woldenii between S. laeve var. laeve and S. praealtum, which instead may be between S. oolentangiense and S. praealtum.

Species classifications

Distribution and habitat
Symphyotrichum laeve varieties are native to Canada, the United States, and Coahuila (Mexico). The species is introduced in Québec and New Brunswick.

S. laeve grows in fields, open woods, and along roadsides in rocky or dry soil and full sun.

Ecology
Symphyotrichum laeve blooms in late summer and early fall. It is pollinated by many native bees and attracts butterflies. It is a larval host for the pearl crescent butterfly (Phyciodes tharos).