Asteraceae: Symphyotrichum laeve
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Family Name
Asteraceae
Common Name
Smooth blue aster
Description
Symphyotrichum laeve is a perennial, herbaceous plant with a fibrous root system and short, creeping rhizomes, sometimes forming loose clumps or small colonies. Mature plants typically reach 40–100 cm in height. Stems are erect, slender, and mostly hairless (glabrous), often with a bluish or glaucous waxy coating. Leaves are alternate, simple, lanceolate to ovate, 4–15 cm long and 1–4 cm wide, with smooth (entire) margins and a pointed tip. Basal and lower stem leaves are larger and may have short petioles, while upper leaves are smaller, clasping the stem with an auriculate (ear-like lobe) base. Leaf surfaces are blue-green, smooth, and glabrous above and below, giving the foliage a characteristic sheen. Flowering occurs from August to October, with inflorescences forming open, branched, leafy panicles up to 30 cm long, each with numerous showy, daisy-like flower heads, subtended by a cylindric involucre, 5–7 mm long, composed of several rows of overlapping, green to purplish, lanceolate phyllaries with translucent margins. Each head contains 15–25 pale blue to lavender ray florets (petals), each 8–15 mm long and 2–3 mm wide, and 15–30 yellow disc florets. Stamens are five per disc floret, with yellow anthers about 1.5 mm long, forming a tube around the style. The pistil consists of a single compound ovary per floret, with a slender style about 3 mm long and a bifid (two-parted) stigma. The fruit is a small, dry, ribbed cypsela (achene), 2–3 mm long, brown when mature in fall; each is topped with a white or pale brown, hair-like pappus 4–6 mm long. Smooth blue aster is native to South Dakota and found throughout the state in prairies, open woodlands, roadsides, and rocky hillsides, typically in well-drained, calcareous, or sandy soils in full sun.
Synonym: Aster laevis
Horticulture Notes
Seed collection: Collect seeds from heads in late fall when achenes are mature and easily detach.
Germination: Seeds require light for germination; sow on the soil surface. Cold, moist stratification (30 days) can improve germination rates.
Vegetative propagation: Propagated by division of rhizomes or basal clumps in spring or fall.
Soils: Prefers well-drained, calcareous or sandy soils; tolerates a range of soil types, including rocky or gravelly sites.
Light: Requires full sun for best growth and flowering.
Water: Moderately drought-tolerant once established; prefers dry to moderately moist soils and does not tolerate prolonged wet conditions.
Additional Notes
Smooth blue aster attracts a wide range of pollinators including bees and butterflies, providing nectar and pollen in late summer and fall. It is popular in native plant gardens, prairie restorations, and naturalized landscapes for its showy flowers and relative ease of care. The species also provides habitat and food resources for small wildlife. It tolerates drought once established and adapts well to varied soil types.