Astilbe 'Washington' (_japonica_ hybrid)

RHS Plant Profile

astilbe 'Washington'

Henry Noblett

Synonyms

Astilbe 'Washington' (× _arendsii_)

Bogs Herbaceous Perennial

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A clump-forming perennial to 75cm with shiny, dark green, divided foliage. Dense, spreading plumes of white flowers are produced in mid- to late summer

Position

Full sun, Partial shade

Soil Types

Clay, Loam

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

Clay Loam

Moisture: Moist but well–drained or Poorly–drained
pH: Acid or Alkaline or Neutral

Position

Full sun Partial shade

Aspect: North–facing or West–facing or East–facing
Exposure: 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: Saxifragaceae
Native to GB/Ireland: No
Foliage: Deciduous
Habit: Clump forming
Genus: Astilbe are rhizomatous herbaceous perennials with attractive, usually ternately divided leaves and erect plume-like panicles of tiny white, pink or purple flowers in summer. The old, brown flower-heads remain attractive in autumn
Name Status: Accepted

How to Grow

Cultivation

Grow in moist but well-drained or boggy soil in dappled shade, or in indirect sun where the soil remains moisture-retentive in summer. Drought intolerant, may be damaged in hot sun. Good for waterside planting. See Astilbe cultivation

Propagation

Propagate by division in late winter or early spring, pot divisions under glass and plant out in late spring

Suggested planting locations and garden types

Cottage and informal garden
Cut flowers
Flower borders and beds

Pruning

Can cut back after flowering, or delay until spring as faded flower spikes can remain attractive in autumn and winter

Pests

Generally pest-free but may be susceptible to vine weevil

Diseases

May be susceptible to powdery mildews and leaf scorch in hot sun