Symphyotrichum novi-belgii

RHS Plant Profile

Michaelmas daisy

Other common names

confused Michaelmas daisy, New York aster

Synonyms

Aster novi-belgii

Herbaceous Perennial

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A clump-forming, herbaceous perennial with narrow, lance-shaped mid-green to purple foliage and masses of daisy-like flowers in shades of purple, lavender-purple or white with yellow centres, which generally appear in the autumn. Heights can vary between 30cm and 180cm with many cultivars having a good resistance to powdery mildews

Position

Full sun, Partial shade

Soil Types

Chalk, Clay, Loam, Sand

Max Height

1-1.5 metres

Max Spread

0.5-1 metres

Size

Time to Maturity: 2–5 years
Max Spread: 0.5-1 metres
Max Height: 1-1.5 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 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): 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, 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

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
Prairie planting
Wildlife gardens
Coastal
Gravel garden
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 but good resistance to powdery mildews