Asteraceae: Symphyotrichum pilosum
Files
Family Name
Asteraceae
Common Name
Hairy aster, frost aster, white oldfield aster
Description
Symphyotrichum pilosum is a perennial, herbaceous plant with a fibrous root system and slender, creeping rhizomes, forming loose colonies or clumps. Mature plants typically reach 50–120 cm in height. Stems are erect, much-branched above, slender, and densely covered with long, spreading white hairs (pilosity) that give the plant a rough texture. Leaves are alternate, simple, and lanceolate to narrowly oblanceolate, ranging from 3–10 cm long and 0.5–2 cm wide, with entire or slightly toothed margins and a pointed tip; basal leaves are larger with winged petioles up to 2 cm long, but most leaves are sessile and become smaller and narrower toward the top. Leaf surfaces are medium to dark green above, lighter below, and both surfaces are hairy, especially along the veins and margins. Flowering occurs from August to October, with inflorescences forming large, open, branched panicles up to 30 cm wide, each with numerous small daisy-like flower heads. The subtending involucres are cylindric, 3–5 mm long, with several rows of overlapping, green, lanceolate phyllaries with translucent margins. Each head contains 15–35 white, occasionally pinkish, ray florets (petals), each 4–8 mm long and 1 mm wide. The disc florets are numerous (10–25 per head), tubular, 4–5 mm long, yellow at first and turning reddish-brown as they age, with five small lobes at the apex. Each disc floret has five stamens with yellow anthers about 1 mm long, forming a tube around the style, and a single compound ovary with a slender style about 2 mm long and a bifid stigma. The fruit is a small, dry, ribbed cypsela (achene), 1.5–2 mm long, gray-brown when mature, each topped with a white, hair-like pappus 3–5 mm long for wind dispersal; fruits mature from September to November. Hairy aster is native to South Dakota and is found throughout the state in prairies, open woodlands, roadsides, old fields, and disturbed areas, especially in dry, sandy, or gravelly soils under full sun.
Synonym: Aster pilosus
Horticulture Notes
Seed collection: Seeds are collected from October to November when flower heads dry.
Germination: Seeds require light for germination; sow on the soil surface. Cold, moist stratification (30–60 days) can improve germination rates.
Propagation: Propagated by division of rhizomes or basal clumps in spring or fall.
Soils: Prefers well-drained sandy to loamy soils.
Light: Full sun to partial shade.
Water: Prefers moderate moisture but tolerates dry conditions.
Additional Notes
Hairy aster provides important late-season nectar and pollen for pollinators such as bees and butterflies. It also serves as habitat and seed source for various small wildlife. In horticulture, it is valued for naturalized landscapes, prairie restorations, and pollinator gardens, especially in areas needing soil stabilization or reclamation. Its hairy foliage distinguishes it and adds textural interest.