Asteraceae: Symphyotrichum sericeum
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Family Name
Asteraceae
Common Name
Silky aster, western silvery aster
Description
Symphyotrichum sericeum is a perennial, herbaceous plant with a fibrous root system and short, thick rhizomes or a branched caudex, forming small, upright clumps. Mature plants typically reach 30–60 cm in height. Stems are erect, unbranched or sparsely branched, and densely covered with fine, silky, silvery hairs that give the plant a distinctive sheen. Leaves are alternate, simple, and narrowly lanceolate to linear, 4–12 cm long and 3–10 mm wide, with entire margins and pointed tips; both surfaces are densely covered with silky, silvery hairs, giving a soft texture and pale blue-green appearance. Basal leaves generally have short petioles and are often withered by flowering time; stem leaves are sessile and become smaller toward the top. Flowering occurs from August to October, with inflorescences forming small, open clusters (panicles or racemes) of showy, daisy-like flower heads, each 2–4 cm across. Each involucre is cylindric, 7–10 mm long, with several overlapping rows of green to purplish lanceolate phyllaries with translucent margins. Each head contains 15–30 bright lavender to purple ray florets, each 10–18 mm long and about 2 mm wide. The disc florets are numerous (15–30 per head), tubular, 5–7 mm long, yellow at anthesis, turning purplish with age, with five small lobes at the tip. Each disc floret has five stamens with yellow anthers about 1.5 mm long, forming a tube around the style, and a single compound ovary with a slender style about 3 mm long and a bifid stigma. The fruit is a small, dry, ribbed cypsela (achene), 2–2.5 mm long, brown when mature, each topped with a pale brown to white, hair-like pappus 4–6 mm long; fruits mature from September to November. Silky aster is native to South Dakota and occurs primarily in dry prairies, open hillsides, rocky outcrops, and sandy or gravelly soils under full sun, often in association with other drought-tolerant prairie species.
Synonym: Aster sericeus
Horticulture Notes
Seed collection: Seeds mature and are collected from October to November as flower heads dry.
Germination: Seeds require light for germination; sow on the soil surface. Cold, moist stratification (30–60 days) improves germination rates.
Vegetative Propagation: Propagated by division of clumps or rhizomes in spring or fall.
Soils: Prefers well-drained loamy to sandy soils.
Light: Full sun to partial shade.
Water: Prefers moderate moisture but tolerates dry conditions.
Additional Notes
Silky aster provides nectar and pollen for pollinators like bees and butterflies late into the growing season. Its attractive, soft foliage and flowers make it a favored choice for native wildflower gardens and prairie restorations. It offers habitat and seeds for small wildlife and is drought tolerant once established.