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Overview
A large genus of flowering perennials in the family Asteraceae, now taxonomically split with North American species largely reclassified into genera including Symphyotrichum, Eurybia, and Doellingeria. Garden plants sold under the name Aster include both the remaining Old World species and North American natives under their historical designation. Plants range from 6 inches to 6 feet (15–180 cm) tall depending on species, with erect to spreading habits. Leaves are lance-shaped to ovate, typically 1–5 inches (2.5–13 cm) long, alternately arranged, and often rough-textured. Composite flower heads are daisy-like, 0.5–2 inches (1.3–5 cm) across, with yellow central disc florets surrounded by 9–35 narrow ray florets in white, pink, lavender, or purple. Bloom occurs primarily late summer to fall, September through October in most zones. Plants spread by rhizomes and self-seed; some species can become aggressive in moist, fertile soils. Powdery mildew is common on lower foliage in summer, particularly on Symphyotrichum species in humid regions.
Native Range
The genus as broadly defined spans North America, Europe, and Asia. North American asters (now largely reclassified as Symphyotrichum and related genera) are native to prairies, open woodlands, roadsides, and moist meadows throughout Canada and the United States. Old World Aster species are native to Europe and Asia, including alpine and subalpine habitats.Suggested Uses
Commonly planted in perennial borders and meadow gardens at 18–36 inch (45–90 cm) spacing depending on species. Valuable late-season nectar source for migrating monarch butterflies and other pollinators. Aggressive spreading species require division every 2–3 years to prevent them from crowding neighboring plants.How to Identify
Appearance
Size & Dimensions
Height6" - 6'
Width/Spread1'6" - 4'
Bloom Information
Blooms August through October in zones 3–8, with peak bloom typically in September. In zones 8–9, bloom may occur earlier in August and finish by late September. Individual flower heads last 1–2 weeks; plants carry multiple successive blooms over a 4–8 week period. Pinching stems back by one-third in June delays bloom by 2–3 weeks and produces more compact plants with increased flower count.Detailed Descriptions
Flower Description
white, pink, lavender, purple with yellow centersFoliage Description
medium to dark greenGrowing Conditions
Sun Requirements
Requires 6-8 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Plant in full sun in well-drained to average soil; most species tolerate a range of soil types but perform poorly in waterlogged conditions. Water regularly during establishment; established plants tolerate moderate dry periods but flowering is reduced without consistent moisture during bud set in late summer. Pinch or cut stems back by one-third in early to midsummer (before July 4 in the northern US) to reduce height and increase branching. Divide clumps every 2–3 years in early spring when the center begins to die out; discard the center and replant outer divisions 18–24 inches (45–60 cm) apart. Powdery mildew affects foliage cosmetically but rarely causes permanent damage; improve air circulation or select mildew-resistant cultivars.Pruning
Cut stems back by one-third in June to control height and promote branching; do not cut back after mid-July as this removes developing flower buds. Cut plants to ground level in late fall after frost or in early spring before new growth emerges. Leave seedheads through winter to provide food for seed-eating birds; cut back in early spring before growth resumes.Pruning Schedule
J
F
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A
M
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early springsummer
Maintenance Level
moderateContainer Growing
✓ Suitable for container growing
Minimum container size: 5 gallons