New York aster
Symphyotrichum novi-belgii · Asteraceae
📷 Benoit Renaud · CC BY 4.0
The gardener's calendar
New york aster is in full bloom: enjoy it, watch watering in hot weather and let spent flowers feed pollinators before pruning.
ID card
- Scientific name
- Symphyotrichum novi-belgii
- Family
- Asteraceae
- Plant type
- Perennial herbaceous
- Foliage
- Deciduous
- Flowering
- August to October
- Mature height
- Approximately 100 cm
- Exposure
- Full sun
- Hardiness
- Very hardy (down to -15°C)
✓ Taxonomy verifiedSource: AI estimate · hardiness: reliability high.
Expert tips
The key tip
Symphyotrichum novi-belgii densifies nicely but burns out easily: divide every autumn (after flowering, September–October) into small divisions of 5–7 cm. Replant only the periphery, discard the old center.
The common mistake
Cutting flowers but skipping yearly division: the plant becomes huge, hollow at the center, prone to powdery mildew and disease.
The pro's trick
Pinch the stems once or twice until mid-July (10 cm tall), then stop.
Seasonal watch
September–November: very prone to powdery mildew at season's end.
Care
Exposure
The smooth aster thrives in full sun, where it receives at least 6 hours of direct light daily. A well-lit exposure strengthens flowering and prevents etiolation. In partial shade, the plant grows but flowers less abundantly.
Watering
Keep the soil regularly moist during growth and flowering, especially during dry periods. Water at the base to avoid foliage moisture. Reduce watering in autumn after flowering and in winter during dormancy.
Soil and planting
Favor well-drained, fertile, and slightly moist soil. Adding compost at planting improves soil structure. Avoid compacted or waterlogged soils that encourage disease.
Fertilizing
Apply balanced fertilizer in spring when growth resumes. A second application in early summer supports flower formation. No fertilizer needed after flowering.
Pruning and maintenance
Pinch young plants in spring to promote compact growth and better branching. After flowering, cut back the plant to 15-20 cm from the ground in late autumn or early winter. Regularly remove spent flowers to prolong blooming.
Diseases and pests
Aster can be affected by powdery mildew and rust in humid or poorly ventilated conditions. Space plants for good air circulation. Also watch for aphids in spring. Good drainage and foliage hygiene reduce risks.
Did you know?
The aster takes its name from the Greek 'aster' meaning 'star', referring to the shape of its flowers. Symphyotrichum novi-belgii, imported from North America in the 17th century, conquered European gardens and remains one of autumn's stars: its delicate inflorescences extend the flowering season when many other plants fade.
Where to buy it
Plant in spring or early autumn, avoiding spells of intense heat. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, April, May, September.
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Tips generated and checked by Viridia — adapt them to your local climate.