Symphyotrichum novi-belgii Tonga ('Dasfour') (Island Series)

RHS Plant Profile
Michaelmas daisy [Tonga]

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Synonyms

Symphyotrichum novi-belgii 'Dasfour'
Aster 'Dasfour'
Aster novi-belgii 'Tonga'
Aster 'Tonga'
Aster 'Dwarf Tonga'
Aster Tonga

Herbaceous Perennial
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A compact, clump-forming perennial with mid-green leaves and clusters of double, bright purple daisy-like flowers with a yellow centre appearing from summer until the autumn.

Position

Full sun, Partial shade

Soil Types

Chalk, Clay, Loam, Sand

Max Height

0.1-0.5 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity
2–5 years
Max Spread
0.1-0.5 metres
Max Height
0.1-0.5 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 North–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
Trade

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. For more advice see aster cultivation

Propagation

Propagate by division in spring. Sow seed in containers in a cold frame in spring or autumn

Suggested planting locations and garden types

  • City and courtyard gardens
  • Cottage and informal garden
  • Coastal
  • Patio and container plants
  • Flower borders and beds

Pruning

No pruning required. Deadhead regularly. Cut back to the ground in late autumn

Pests

May be susceptible to aphids, eelworms (leaf and bud), Michalmas daisy mite, slugs and snails

Diseases

May be susceptible to Fusarium wilt, grey mould, leaf spot and powdery mildew