Aconitum japonicum

RHS Plant Profile
Japanese monk's hood

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Japanese monk's hood RHS
Herbaceous Perennial
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A clump-forming, upright perennial to around 1m tall with deeply divided, glossy dark green leaves to 16cm long. Panicles of hooded, deep blue flowers are borne in 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
pH
Acid or Alkaline or Neutral

Position

Full sun Partial shade
Aspect
West–facing or East–facing or North–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
Ranunculaceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Clump forming
Potentially harmful
TOXIC if eatenavoid skin contact. Wear gloves and other protective equipment when handling. Pets: TOXIC if eatenavoid skin contact - see the HTA guide to potentially harmful plants for further information and useful contact numbers
Genus
Aconitum can be herbaceous perennials or biennials with lobed leaves and racemes or panicles of showy, hooded flowers
Name Status
Correct
Plant Range
Japan

How to Grow

Cultivation

Best grown in moisture-retentive fertile soil in partial shade but sun and most soils are tolerated

Propagation

Propagate by division in autumn or late winter to maintain vigour, although plants can be slow to re-establish. Use gloves when handling plants

Suggested planting locations and garden types

  • Cottage and informal garden
  • Wildlife gardens
  • Flower borders and beds

Pruning

No pruning required except cutting back dead stems; use protective gloves

Pests

May be susceptible to aphids

Diseases

May be susceptible to fungal stem rot, powdery mildews, and Verticillium wilt