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Herbaceous Perennial

Symphyotrichum cordifolium
  • RHS Plants for pollinators

blue wood aster

A clump-forming perennial, up to 1.5m high, with upright, branching stems and oval to heart-shaped green leaves. Clusters of small daisy-like flowers, in pale violet, blue or occasionally white, are produced from late summer well into autumn

Synonyms
Aster sagittifolius Wed.
Aster cordifolius
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Size
Ultimate height
1–1.5 metres
Time to ultimate height
2–5 years
Ultimate spread
0.5–1 metres
Growing conditions
Chalk
Clay
Loam
Sand
Moisture
Moist but well–drained
pH
Acid, Alkaline, Neutral
Colour & scent
StemFlowerFoliageFruit
Spring Green
Summer Blue Purple White Green
Autumn Blue Purple White Green
Winter
Position
  • Full sun
  • Partial shade
Aspect

East–facing or South–facing or West–facing

Exposure
Exposed or Sheltered
Hardiness
H7
Botanical details
Family
Asteraceae
Native to GB / Ireland
No
Foliage
Deciduous
Habit
Clump forming
Genus

Symphyotrichum includes around 90 species of annuals, biennials and perennials, mostly spread through the Americas, that were formerly included within the genus Aster. Leaves are simple, lance-shaped and entire, but it is their daisy-like flowerheads that they are grown for; central disc florets are typically yellow, surrounded by strap-shaped ray florets in shades of pink, blue, purple or white

Name status

Correct

Plant range
USA

How to grow

Cultivation

Grow in fertile, moisture-retentive soil, in sun or part shade; add mulch after cutting back in autumn. Plants may need support, see staking: perennials. Divide every third year to retain vigour and flower quality. See aster cultivation

Propagation

Propagate by seed or by division in spring, replanting only vigorous young shoots

Suggested planting locations and garden types
  • Cottage and informal garden
  • Prairie planting
  • Wildlife gardens
  • Coastal
  • Flower borders and beds
  • Cut flowers
Pruning

Cut stems close to the ground in late autumn

Pests

May be susceptible to leaf and bud eelworm, aphids, slugs and snails

Diseases

May be susceptible to Fusarium wilt, powdery mildews, leaf spots and grey moulds

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