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Impatiens glandulifera

policeman's helmet

Balsaminaceae

Western Himalayas (India, Pakistan, Nepal)

Attracts Pollinators Fragrant (moderate)

SunPart Shade – Full Sun

WaterHigh

Overview

Impatiens glandulifera is a massive annual in the balsam family (Balsaminaceae) reaching 3-10 feet (0.9-3 m) tall with an 18-36 inch (45-90 cm) spread. Few annual herbaceous plants in the Pacific Northwest reach similar stature within a single growing season. Stems are erect, succulent, hollow, smooth, green to reddish-purple, up to 2 inches (5 cm) in diameter at the base, with swollen nodes. Leaves are opposite or in whorls of 3, lance-shaped to elliptic, 4-8 inches (10-20 cm) long, with sharply serrate margins and red glands (the source of the name glandulifera) at the base of each leaf. Flowers are large, 1-1.5 inches (2.5-4 cm) long, pink to purple (occasionally white), helmet-shaped with a short recurved spur, borne in racemes of 2-14 from the upper leaf axils, carrying a sweet fragrance. Fruit is a club-shaped capsule 0.6-1 inch (15-25 mm) long that explodes when ripe, projecting seeds up to 20 feet (6 m). A single plant produces 500-4,000 seeds. Seeds disperse by the explosive mechanism and by water along streams and rivers. I. glandulifera is listed as a Class B noxious weed in Washington State. Dense monoculture stands form along waterways, outcompeting native riparian vegetation.

Native Range

Impatiens glandulifera is native to the western Himalayas of India, Pakistan, and Nepal, occurring along montane stream corridors at 6,000-13,000 feet (1,800-4,000 m). Introduced to Europe in 1839 as an ornamental and to North America subsequently, the species is widely naturalized in the Pacific Northwest, northern Europe, and parts of New Zealand, primarily along rivers, streams, and wet disturbed areas.

Suggested Uses

Used in noxious weed identification training and community-organized invasive species removal along Pacific Northwest waterways. The explosive seed dispersal mechanism is used in botanical teaching alongside the native I. capensis. Studied in riparian invasion ecology, pollinator competition (the species outcompetes native flowers for bumblebee visits due to high nectar production), and seed dispersal by water (hydrochory).

How to Identify

Separated from Impatiens capensis (spotted jewelweed) by the much larger size (3-10 feet / 0.9-3 m versus 2-5 feet / 0.6-1.5 m), the pink to purple flowers (versus orange), the opposite or whorled leaves (versus alternate), and the red glands at the leaf bases. Stems are much thicker, up to 2 inches (5 cm) in diameter, hollow, and readily crushed. The large helmet-shaped flowers with a sweet fragrance are diagnostic. Both species share the explosive seed capsule mechanism.

Appearance

Size & Dimensions

Height3' - 10'

Width/Spread1'6" - 3'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~8 weeks

Summer Fall

Flowers appear July through October. Individual flowers last 2-3 days. Racemes of 2-14 flowers bloom sequentially over 6-8 weeks. In the Pacific Northwest, peak bloom occurs in August through September. The sweet fragrance attracts bumblebees, which are the primary pollinators. Capsules mature 3-4 weeks after pollination and explode at the slightest touch.

Detailed Descriptions

Flower Description

Pink to purple (occasionally white) helmet-shaped flowers 1-1.5 inches (2.5-4 cm), with short recurved spur and sweet fragrance

Foliage Description

Dark green, lance-shaped to elliptic, opposite or in whorls of 3, with sharply serrate margins and red glands at the leaf base

Growing Conditions

Sun Requirements

SunPartial Shade SunFull Sun

Requires 4-8 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

loam silt clay

Drainagemoist

Water & Climate

Water Needs

High

Frost Tolerance

tender

Care & Maintenance

Care Guide

I. glandulifera is listed as a Class B noxious weed in Washington State; management focuses on pulling before seed capsule formation. The succulent stems and shallow root system make hand-pulling straightforward — plants uproot with minimal effort from moist soil. Pulling timed before capsules mature (July in most PNW sites) prevents explosive seed dispersal. In riparian corridors, upstream populations are addressed first, since seeds disperse downstream by water. Large infestations are managed by mowing or cutting at the base before flowering. Cut stems left on moist ground can re-root at nodes. The annual life cycle means 1-3 years of consistent removal before seed set depletes the soil seed bank (seeds viable 2-3 years). Community-organized pull events along waterways are a common management approach.

Pruning

Pruning is not applicable. Plants are pulled or cut at ground level before capsules form. The hollow, succulent stems snap easily. Cut material is piled on dry ground or removed from the riparian corridor, since stem nodes on moist soil regenerate.