Culture
Easily grown in moist, well-drained soils in full sun to part shade. Best growth typically occurs in moist, semi-shaded woodland areas. Tolerates full sun in cool summer climates, but appreciates some part shade in climates where summer temperatures consistently exceed 90 degrees F. Tolerates periodic flooding. Stems may be pinched back in late spring to early summer if shorter plants are desired. Plants can spread aggressively by self-seeding. This plant is considered weedy in some areas of the U.S.
Noteworthy Characteristics
Symphyotrichum pilosum, commonly known as frost aster (hairy stems appear to be covered with thick frost) or hairy white old-field aster (hairy white-flowered plants often found growing in old fields) or awl aster (awl-like appearance of narrow pointed involucral bracts), is an herbaceous perennial in the aster family that typically grows to 4’ tall and as wide on one or more leafy, sometimes-branching stems. It is native to upland prairies, weedy meadows, pastures, open woodlands, limestone glades, abandoned/old fields, railroad right of ways, roadsides and waste ground from Quebec and Ontario south to Texas and Florida. It is commonly found throughout most of Missouri.
Frost aster is particularly noted for its extremely hairy stems and hairy leaves, except for S. pilosum var. pringlei which has glabrous stems and leaves. Leaves (1-4” long) are alternate, simple, lance-elliptic to lance-linear with toothless or shallowly-toothed margins and pointed tips. Basal leaves are spatulate and rounded at the tip with winged sheathing stalks. Leaves significantly decrease in size as they ascend the stems.
Flowers (each to 3/4” across) in branching clusters rising from the stem tops and upper leaf axils bloom from summer to fall (August to October). Each flower features 15-35 white rays which surround a center disc of 20-40 pale yellow disc flowers. Disc flowers turn reddish-purple with age. Flowers are followed by a fruit (dry seed with a tuft of white hairs). With the help of the white hairs, seeds are distributed to new locations by wind.
This species is very similar to S. ericoides which inhabits the same kinds of open, prairie-like habitats.
Aster pilosus is a synonym of the within plant. A number of different species of aster which were originally assigned to the genus Aster, including the within species, have now been reclassified to the genus Symphyotrichum, but with retention of their original aster common names.
Genus name comes from the Greek symph meaning coming together and trich meaning hair in possible reference to the flower anthers.
Specific epithet means covered with long soft hairs.
Problems
No serious insect or disease problem. Taller plants may need some support.
Uses
Borders. Open woodland areas. Prairies. Cottage gardens. Mass or group.