Aster divaricatus

Description

Aster divaricatus – white wood aster

Botanical name: Aster divaricatus (syn. Eurybia divaricata)
Common names: White wood aster
Family: Asteraceae (daisy family)
Plant type: Herbaceous perennial
Habit: Upright, clump-forming
Pot size: 2–3 litre pot
Eventual size: Approx. 45–60cm tall × 45cm spread
Foliage: Lance-shaped green leaves on distinctive wiry, near-black, zig-zagging stems; deciduous
Flowers: Airy clouds of small white daisy flowers with dark centres, ageing to pinkish, late summer into autumn (August–October)
Scent: Not notably scented
Aspect / light: Partial to full shade; tolerates some sun
Soil: Well-drained; tolerates dry shade; humus-rich; any pH
Hardiness: RHS H7 (very hardy, below −20°C); USDA zones 4–8
Exposure: Open, sunny; good air circulation
Native range: Garden form; the parent species are native to North America
Toxicity / pet & child safety: Generally considered non-toxic to people and pets

Aster divaricatus, white wood aster, produces airy clouds of small white dark-centred daisies on wiry near-black stems, and — unusually — thrives in dry shade. A superb, graceful aster for difficult shady spots.

GardenAdvice notes

One of the finest of all late-season perennials, this aster (Michaelmas daisy) smothers itself in cheerful daisy flowers from late summer well into autumn, bringing invaluable colour just as the garden fades — and a crucial late source of nectar for bees and butterflies. Unusually for an aster, it tolerates dry shade well and rarely troubled by mildew.

Growing & planting

Plant in spring or autumn in moist but well-drained, fertile soil, with good air circulation — asters dislike drying out, which stresses them and encourages mildew, so reliable moisture matters. It is unusually shade-tolerant. Space appropriately for its size. Water in dry spells.

Care & maintenance

Low-maintenance. Keep the soil from drying out. Taller sorts may need support, or can be given the ‘Chelsea chop’ (cutting back by a third in late spring) for bushier, self-supporting growth. Cut down old growth in late winter, leaving seed heads for winter interest if wished. Lift and divide every two to three years in spring to keep it vigorous and healthy — the key to good, mildew-free plants.

Propagation

• Division: Lift and divide established clumps in spring, as growth begins.

Pests & diseases

Michaelmas daisies can be prone to powdery mildew, especially if they dry out or lack air movement. Keeping them moist, dividing regularly and ensuring good air circulation are the best defences. Unusually for an aster, it tolerates dry shade well and rarely troubled by mildew.

Uses in the garden

Superb for the front to middle of shady and woodland borders, under shrubs and in dry shade, where few other asters will grow, its airy white daisies and dark stems weaving beautifully through other planting.

Wildlife value

One of the very best plants for late-season pollinators: the daisy flowers are a crucial source of nectar for bees and butterflies in autumn, when little else is in bloom.

Toxicity & safety

Michaelmas daisy is generally regarded as non-toxic to people and pets.

GardenAdvice tip

The white wood aster is the aster to grow in shade — it actually thrives in dry shade under trees and shrubs, where most asters would sulk, weaving its airy white daisies and dark wiry stems through other plants. Its lax, relaxed habit is part of its charm; let it flop gently among neighbours, and enjoy that it’s rarely troubled by the mildew that affects the sun-lovers.

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