ASTER Varieties and Cultivation Tips for GardenersAsters are beloved perennial and annual flowering plants prized for their late-season blooms, vibrant colors, and ability to attract pollinators. Gardeners value them for borders, cut flowers, containers, and naturalized spaces. This article covers the main aster types, popular cultivars, planting and care practices, pest and disease management, propagation methods, and design ideas to help you grow healthy, floriferous asters.
Overview: What Are Asters?
Asters belong to the family Asteraceae and historically included many species in the genus Aster. Taxonomic revisions moved many Old World species to other genera (such as Symphyotrichum, Eurybia, and Aster), but the common name “aster” still applies broadly to similar star-shaped daisy-like flowers. Most garden asters bloom from late summer into fall, providing crucial nectar for bees and butterflies as other flowers wane.
Major Types and Species
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New England Asters (Symphyotrichum novae-angliae)
- Tall, upright plants (3–6 ft) with dense, daisy-like flower heads.
- Colors: purple, pink, red, white.
- Great for back borders and cutting.
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New York Asters (Symphyotrichum novi-belgii)
- Typically shorter (1–3 ft) with large, showy blooms.
- Very popular in cottage gardens and mixed borders.
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Michaelmas Daisies
- Common name for several late-blooming asters; overlaps with New England and New York types.
- Notable for flowering around the feast of Michaelmas (late September).
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Alpine and Heath Asters (Aster alpinus and related)
- Low-growing, rock-garden types with early-to-mid-summer blooms.
- Often used in alpine beds, containers, and edges.
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Aromatic Asters (Symphyotrichum oblongifolium)
- Compact, fragrant-leafed species useful for front-of-border plantings.
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Other related genera
- Eurybia, Ionactis, Doellingeria, and Coreopsis-like genera contain species often called asters.
Popular Cultivars Worth Trying
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‘King George’ (formerly Aster novi-belgii ‘King George’)
- Large, rosy-purple flowers; prolific bloomer.
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‘Wood’s Pink’ (Symphyotrichum novae-angliae ‘Wood’s Pink’)
- Soft pink blooms; good for mixed borders.
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‘Purple Dome’ (Aster dumosus ‘Purple Dome’)
- Compact, mound-forming; excellent for edging and containers.
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‘Mönch’ (Symphyotrichum novi-belgii ‘Mönch’)
- Deep violet blooms; sturdy stems for cutting.
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‘Little Carlow’ (Aster x frikartii ‘Little Carlow’)
- Long bloom period, lilac flowers; good disease resistance.
Planting and Site Selection
- Light: Full sun (6+ hours/day) produces the best flowering; partial shade tolerated in hot climates.
- Soil: Prefer well-draining, moderately fertile soil with pH 5.8–7.0.
- Spacing: Provide 12–36 inches between plants depending on mature size to ensure airflow.
- Planting time: Best planted in spring after last frost or in early fall (allowing roots to establish before winter).
- Companion plants: Combine with ornamental grasses, sedums, rudbeckia, and late-season salvias for layered fall interest.
Watering and Fertilization
- Watering: Keep soil consistently moist during establishment. Once established, many asters tolerate short dry spells but prefer regular moisture—especially during bud set.
- Fertilizer: Apply a balanced slow-release fertilizer in spring. Avoid high-nitrogen feeds which encourage lush foliage at the expense of flowers.
Pruning, Deadheading, and Dividing
- Pinching: Pinch back stems in early summer to encourage bushiness and delay flowering for a stronger post-pinching bloom display.
- Deadheading: Remove spent blooms to extend the flowering period.
- Cutting back: After heavy frost, cut back to ground level for many perennials. Some gardeners leave stems through winter for interest and seed-eating birds, cutting back in late winter.
- Division: Divide every 2–4 years in early spring or fall to rejuvenate clumps, reduce disease, and control size.
Pests and Diseases
- Powdery mildew: Common in humid conditions—improve air circulation, avoid overhead watering, choose resistant cultivars, and apply fungicides if necessary.
- Rust and leaf spot: Remove affected foliage and maintain good sanitation.
- Aphids, thrips, and spider mites: Monitor for infestations; use insecticidal soap or strong water sprays to control.
- Crown rot/Root rot: Avoid waterlogged soils; ensure good drainage and plant on slight mounds in poorly draining areas.
Propagation Methods
- Seed: Some asters readily self-seed or can be started from seed sown indoors 6–8 weeks before last frost. Hybrids may not come true from seed.
- Division: The quickest way to propagate perennials—divide established clumps into sections with healthy roots.
- Cuttings: Softwood cuttings in late spring to early summer root well for many species.
Design Uses and Seasonal Interest
- Borders and backdrops: Tall New England asters provide late-season height and color.
- Pollinator gardens: Asters are late nectar sources for bees, butterflies, and migrating monarchs.
- Containers and edging: Compact cultivars and alpine asters suit containers and front-of-border plantings.
- Naturalizing: Some species spread and naturalize in meadows and prairie restorations.
Troubleshooting Common Problems
- Spindly growth: Ensure full sun; pinch to encourage bushiness; divide overcrowded clumps.
- Poor flowering: Check for excessive nitrogen, insufficient light, or overcrowding.
- Reoccurring mildew: Improve spacing, increase sunlight, and select mildew-resistant varieties.
Quick Care Plan (Seasonal Checklist)
- Spring: Divide if needed; apply slow-release fertilizer; mulch light layer.
- Early summer: Pinch back for bushier growth if desired.
- Mid–late summer: Monitor water; begin deadheading as blooms fade.
- Fall: Enjoy peak bloom; leave some stems for birds if desired; cut back after hard frost or in late winter.
Asters are versatile, resilient, and valuable for fall color and pollinators. With the right site, regular maintenance, and careful cultivar selection, gardeners can enjoy weeks of vibrant late-season blooms.