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Petasites, Genus, albus, Species,

Genus & species

white butterbur

Asteraceae

Mountains of Europe and south-west Asia

Attracts Pollinators Deer Resistant

SunPart Shade – Full Shade

WaterHigh

HardinessZones 5–8

Overview

Petasites albus, white butterbur, is a vigorous, rhizomatous perennial in the daisy family (Asteraceae) that spreads by stout underground stems to form broad colonies. In early spring, before the leaves, thick stalks 4-12 inches (10-30 cm) tall rise carrying dense rounded heads of small whitish to cream flowers; plants are dioecious, with separate male and female clumps. After flowering the large basal leaves expand, rounded to heart-shaped and 8-16 inches (20-40 cm) across, green above and grey-felted beneath, on long stalks that can reach 24 inches (60 cm). It grows in damp, shaded ground along streams, ditches, and woodland edges on moist, fertile soil, where the spreading rhizomes can quickly cover large areas. All parts contain pyrrolizidine alkaloids, which are toxic to the liver if eaten. One limitation is its strongly invasive, colony-forming habit, which makes it difficult to remove once established. The bold foliage dies back to the rhizome each autumn and reappears the following spring.

Native Range

Petasites albus is native to the mountains and uplands of Europe and into south-west Asia, growing along streams, in damp woodland, and on shaded slopes. It has naturalised beyond its native range in parts of Britain and northern Europe.

Suggested Uses

Used as bold groundcover in large, damp, shaded sites such as stream banks, pond margins, and wild woodland gardens where its spread can be tolerated. The early flowers give nectar to emerging insects and the broad leaves suppress weeds over wide areas.

How to Identify

White butterbur is recognised in early spring by squat flower stalks 4-12 inches (10-30 cm) tall bearing crowded heads of whitish to cream flowers before any leaves show. The large rounded to heart-shaped basal leaves that follow are 8-16 inches (20-40 cm) wide, green above and grey-woolly beneath. The whitish flowers separate it from the pink-flowered common butterbur (Petasites hybridus). Its spreading rhizomes form dense, weed-smothering patches.

Appearance

Size & Dimensions

Height8" - 2'

Width/Spread2' - 4'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~4 weeks

Flowers: March–April

Spring

Flowering occurs in early spring, March to April, before the foliage emerges. Dense club-shaped heads of small whitish to cream flowers open on thick stalks, with male and female flowers on separate plants, and draw early bees and other insects. Female heads lengthen as fluffy, wind-borne seed ripens, though much of the spread is by rhizome rather than seed.

Detailed Descriptions

Flower Description

whitish to cream

Foliage Description

green above, grey-felted beneath

Growing Conditions

Sun Requirements

SunPartial Shade SunFull Shade

Tolerates up to 4 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.5 (Acidic to alkaline)

3579

Soil Types

loam clay

Drainagemoist

Water & Climate

Water Needs

High

Frost Tolerance

hardy

Care & Maintenance

Care Guide

Petasites albus grows in part to full shade on permanently moist, fertile soil beside water and in damp woodland, and is hardy in roughly USDA zones 5 to 8. It spreads aggressively by thick rhizomes and can overwhelm smaller plants, so it is confined to large, contained, or wild settings. Once established it needs no feeding or watering in suitable damp ground. All parts contain pyrrolizidine alkaloids that are toxic to the liver, so it is not used in food or herbal preparation without specialist processing. Removal requires repeated digging of the deep rhizomes over several seasons. It has few pests of concern.

Pruning

Spent flower stalks are removed in spring to limit seeding, and the large leaves are cut down as they collapse in autumn. Rhizome spread is checked by slicing around the clump or growing it within a buried barrier. Sections of rhizome left in the soil regrow, so thorough removal is needed to clear it.