Symphyotrichum oolentangiense

RHS Plant Profile

sky blue aster

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Other common names

blue devils

Synonyms

Aster oolentangiensis
Aster azureus

Herbaceous Perennial

Clump-forming perennial with slender flowering stems about 90cm in height with lance to heart-shaped rough-hairy, mid-green leaves. From late summer to autumn bears spreading clusters of daisy-like pale lavender blue flowerheads to 2.5cm across, with yellow centres

Position

Full sun, Partial shade

Soil Types

Chalk, Clay, Loam, Sand

Max Height

0.5-1 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity: 2–5 years
Max Spread: 0.1-0.5 metres
Max Height: 0.5-1 metres

Growing Conditions

Chalk Clay Loam Sand

Moisture: Moist but well–drained or Well–drained
pH: Acid or Alkaline or Neutral

Position

Full sun Partial shade

Aspect: East–facing or South–facing or West–facing
Exposure: Exposed or Sheltered
Hardiness

Hardiness Ratings

All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

H1A: under glass all year (>15C)
H1B: can be grown outside in the summer (10 - 15)
H1C: can be grown outside in the summer (5 - 10)
H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
H4: hardy through most of the UK (-10 to -5)
H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
H6: hardy in all of UK and northern Europe (-20 to -15)
H7: hardy in the severest European continental climates (< -20): H7

Colour & Scent

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

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

How to Grow

Cultivation

Grow in moderately fertile, moist but well-drained soil in full sun or light shade. Stake tall plants in early spring, see staking perennials. See aster cultivation for further advice

Propagation

Propagate by division in spring or root softwood basal cuttings in spring; division can be carried out every third year to maintain vigour

Suggested planting locations and garden types

Coastal
Cottage and informal garden
Gravel garden
Prairie planting
Wildflower meadow
Wildlife gardens
Cut flowers
Flower borders and beds

Pruning

Cut stems close to the ground in late autumn

Pests

May be susceptible to leaf and bud eelworms, slugs and snails

Diseases

May be susceptible to Verticillium wilt, Powdery mildews and grey moulds