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Epilobium brachycarpum

panicled willowherb

Onagraceae Western North America

Attracts Pollinators Drought Tolerant

Native to North America

SunFull Sun

WaterLow · drought-tolerant

Overview

Epilobium brachycarpum is a summer annual in the evening primrose family (Onagraceae), reaching 1-5 feet (30-150 cm) on slender, much-branched stems that often turn reddish with age. Narrow, linear to lance-shaped leaves 0.4-2 inches (1-5 cm) long are alternate and sparse on the upper stem. The plant divides into an open, airy panicle in its upper half, the trait behind its common name. Flowers are small, 0.1-0.3 inch (3-8 mm) across, with four notched petals ranging from pale pink to white above a four-lobed stigma. Each flower yields a slender capsule 0.2-0.4 inch (5-10 mm) long that splits to release seeds tipped with white hairs for wind dispersal. E. brachycarpum germinates with autumn or spring moisture and completes its life cycle in a single season. It colonizes dry, open, disturbed ground including roadsides, burned areas, and overgrazed range, and can spread densely where it self-sows. Plants senesce by late autumn, leaving dry standing stems. As a short-lived annual, it leaves no permanent structure and dies back completely each year.

Native Range

Native to western North America, ranging from British Columbia and Alberta south to Baja California and east to the western Great Plains. It grows on dry slopes, open woodland, sagebrush flats, and disturbed sites from sea level to about 9,800 feet (3,000 m).

Suggested Uses

Used in habitat restoration and erosion control on disturbed or burned sites, where it establishes quickly from seed. It also appears in informal native and wildlife plantings. Small bees and flies visit the flowers for nectar and pollen.

How to Identify

Recognized by its tall, slender, freely branched reddish stem topped with an open panicle of small four-petaled flowers, each petal notched at the tip. The narrow linear leaves are widely spaced and often curl or drop from the lower stem by flowering time. Seed capsules are short for the genus, only 0.2-0.4 inch (5-10 mm) long, splitting into four sections to release plumed seeds. The pale pink to white flowers under 0.3 inch (8 mm) wide separate it from the larger-flowered fireweeds.

Appearance

Size & Dimensions

Height1' - 5'

Width/Spread6" - 1'6"

Colors

Flower Colors

pink

white

Foliage Colors

green

Bloom Information

Bloom Period

~14 weeks

Summer Fall

Flowering runs from July to October, peaking in late summer. Individual flowers open a few at a time across the branched panicle over several weeks. Bloom is heaviest where summer moisture persists and tapers in drought. Flowers are self-compatible and frequently self-pollinate.

Detailed Descriptions

Flower Description

pale pink to white

Foliage Description

green to reddish-green

Growing Conditions

Sun Requirements

SunFull Sun

Requires 6-12 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(Neutral)

357912

Soil Types

sand loam rocky

Drainagewell drained

Water & Climate

Water Needs

Low

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Epilobium brachycarpum grows in full sun on dry, well-drained sandy, rocky, or loamy soils of low fertility. It tolerates drought once established and needs no supplemental water in most climates. Soil pH from about 5.5 to 7.5 suits it. The species reseeds freely and can spread beyond its intended area when seed heads mature. It needs no fertilizer and establishes in poor, disturbed ground where many plants fail. Growth is fastest with spring moisture, after which the plant flowers and sets seed within one season.

Pruning

No pruning is needed for this annual. Spent plants can be pulled or cut at the end of the season to limit self-seeding. Cutting seed heads before the capsules split reduces volunteer seedlings the following year.