Aster thomsonii

RHS Plant Profile
Thomson's aster

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Thomson's aster RHS
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Herbaceous Perennial
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A clump-forming perennial, to 1m tall, with oval, toothed leaves, up to 10cm long, on hairy stems. Flowerheads, up to 5cm across, comprising lavender-blue rays and a central yellow disk, are held on slender branches from late summer into autumn

Position

Full sun

Soil Types

Chalk, 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 Loam Sand
Moisture
Moist but well–drained or Well–drained
pH
Alkaline or Neutral

Position

Full sun
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
Bushy
Genus
Aster can be perennials, annuals or subshrubs, mostly with narrow leaves, and solitary or clustered, daisy-like flowers
Name Status
Correct

How to Grow

Cultivation

Grows best in full sun in a well-drained, alkaline soil with moisture in the spring and summer

Propagation

Propagate by division

Suggested planting locations and garden types

  • Cottage and informal garden
  • City and courtyard gardens
  • Coastal
  • Wildlife gardens
  • Flower borders and beds

Pruning

Cut back in late autumn

Pests

May be susceptible to Tarsonemid mite

Diseases

May be susceptible to Verticillium wilt and grey moulds