Synurus excelsus

RHS Plant Profile
large deltoid synurus

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large deltoid synurus RHS
large deltoid synurus RHS
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Herbaceous Perennial

A deciduous, clump-forming perennial with triangular, shallowly-lobed leaves and stout stems to 1.8m tall bearingnodding flowerheads to 6cm across made up of deep reddish-purple florets in autumn

Position

Full sun

Soil Types

Chalk, Clay, Loam, Sand

Max Height

1.5-2.5 metres

Max Spread

0.5-1 metres

Size

Time to Maturity
1–2 years
Max Spread
0.5-1 metres
Max Height
1.5-2.5 metres

Growing Conditions

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

Position

Full sun
Aspect
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)
H4

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Asteraceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Columnar upright
Genus
Synurus have a thick stem and can reach heights of 1.8m. They produce large, nodding flowers with purple florets up to 6cm wide.
Name Status
Correct

How to Grow

Cultivation

Grows best in a sunny position in a moist but well-drained soil

Propagation

Propagate by seed or by division

Suggested planting locations and garden types

  • Wildlife gardens
  • Architectural
  • Cut flowers
  • Flower borders and beds

Pruning

Cut back in late winter or early spring

Pests

Generally pest-free

Diseases

Generally disease-free