Epilobium ciliatum

RHS Plant Profile
American willowherb

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American willowherb RHS
Herbaceous Perennial

A fast-growing, clump-forming herbaceous perennial to 1.5m high, with narrowly ovate, finely toothed green leaves often tinged with red, and numerous small, trumpet shaped pink or white flowers

Position

Full shade, Full sun, Partial shade

Soil Types

Chalk, Clay, Loam, Sand

Max Height

1-1.5 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity
1–2 years
Max Spread
0.1-0.5 metres
Max Height
1-1.5 metres

Growing Conditions

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

Position

Full shade 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)
H4

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Onagraceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Columnar upright
Genus
Epilobium can be annuals or perennials, sometimes invasive, with erect stems bearing willowy leaves and showy, 4-petalled flowers in terminal racemes
Name Status
Unresolved

How to Grow

Cultivation

Grows best in moist soil in well-lit conditions, but will tolerate shade and a range of soil types. See willowherbs for more information

Propagation

Propagates by seed produced prolifically through the growing season and wind-dispersed. In favourable conditions, life cycle from germination to seed production can complete in ten weeks

Suggested planting locations and garden types

  • Wildlife gardens

Pruning

No pruning required

Pests

Generally pest-free

Diseases

Generally disease-free