Petasites japonicus

RHS Plant Profile

giant butterbur

RHS

Herbaceous Perennial

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A substantial plant, producing huge suborbicular leaves to 90cm across, reaching 150cm in height, in summer. Flowers are cream to white, borne in February on stout erect stems to 30cm. The plant normally available is nearly always the male plant

Position

Full shade, Partial shade

Soil Types

Clay, Loam

Max Height

1-1.5 metres

Max Spread

4-8 metres

Size

Time to Maturity: 2–5 years
Max Spread: 4-8 metres
Max Height: 1-1.5 metres

Growing Conditions

Clay Loam

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

Position

Full shade Partial shade

Aspect: North–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): 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
Genus: Petasites are perennial plants, usually large, with thick rhizomes or stems. Leaves are often very large and either heart-shaped or kidney-shaded. Scapes or stems many-headed, with any leaves usually reduced to scales. Flowers dioecious in usually rayless heads, purple or white, rarely yellowish, borne in panicles or racemes at the ends of the scapes
Name Status: Correct
Plant Range: Korea China Japan

How to Grow

Cultivation

Grow in deep, humus-rich, fertile soil that is permanently moist but not stagnant, in partial or full shade. A large, vigorous, spreading plant that has the potential to become a nuisance if not managed well

Propagation

Divide in spring

Suggested planting locations and garden types

Wildlife gardens
Low Maintenance

Pruning

Remove the old foliage before the onset of new growth in late winter

Pests

Generally pest-free

Diseases

Generally disease-free