Symphyotrichum novi-belgii 'White Swan'

RHS Plant Profile
Michaelmas daisy 'White Swan'

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Synonyms

Aster novi-belgii 'White Swan'

Plants for pollinators
Herbaceous Perennial

A clump-forming, herbaceous perennial to 90cm, with narrow, lance-shaped, mid-green leaves on slender, branched stems. Produces sprays of white daisies, ageing to pink, from late summer to early autumn

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
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)
H6

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
Unresolved

How to Grow

Cultivation

Thrives in fertile, moist but well drained soil in sun or partial shade. Plants will benefit from mulching in autumn, and division every few years to maintain vigour. Will not tolerate waterlogging in winter, and may need support, see staking (perennials). For more advice see aster cultivation

Propagation

Propagate by division in spring, replanting only vigorous young shoots

Suggested planting locations and garden types

  • Cottage and informal garden
  • City and courtyard gardens
  • Coastal
  • Gravel garden
  • Patio and container plants
  • Wildlife gardens
  • Cut flowers
  • Flower borders and beds

Pruning

Cut stems close to the ground in late autumn

Pests

May be susceptible to aphids, leaf and bud eelworms, slugs, snails and tarsonemid mite

Diseases

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