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Cardamine impatiens

narrow-leaved bittercress

SunPart Shade – Full Shade

Overview

Cardamine impatiens is an annual to biennial plant in the mustard family (Brassicaceae), growing 8–24 inches (20–60 cm) tall on slender, branching stems. Its leaves are pinnately compound with many small, narrow, toothed leaflets, and the leaf bases clasp the stem with a pair of fringed, ear-like lobes. From spring into summer it bears tiny white flowers about 0.1 inch (3 mm) across, often with petals so small or absent that the flowers look green; these are followed by slender upright pods. As the pods ripen, they split explosively, flinging seeds up to several feet from the parent plant. Native to Europe and Asia, it has become an aggressive invader of shaded habitats in the northeastern and midwestern United States, spreading through moist woods, floodplains, trail edges, and ravines where it can carpet the ground and crowd out native woodland plants. It germinates in fall or spring, tolerates deep shade, and self-pollinates, so a single plant can found a new colony. It is shallow-rooted and pulls easily, but the explosive seed spread makes it hard to contain.

Native Range

Cardamine impatiens is native to Europe and temperate Asia. It has naturalized in eastern North America, where it is listed as an invasive species in several northeastern and midwestern states and spreads in shaded, moist habitats.

Suggested Uses

Cardamine impatiens has no horticultural use and is managed as an invasive weed in shaded habitats of eastern North America. Where it appears in woodland gardens and natural areas, it is removed to protect native ground-layer plants. It is listed for control in several state invasive-species programs.

How to Identify

Identify Cardamine impatiens by its pinnately compound leaves with many narrow, toothed leaflets and the fringed, ear-like lobes that clasp the stem at each leaf base. The tiny white flowers often lack visible petals and look greenish. The clasping fringed leaf bases and explosively splitting upright pods separate it from native bittercresses such as C. pensylvanica, which lack the clasping lobes.

Appearance

Size & Dimensions

Height8" - 2'

Width/Spread4" - 10"

Colors

Flower Colors

white

Foliage Colors

green

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~8 weeks

Spring Summer

Tiny white or petalless flowers open from April into June, scattered along the branch tips. Bloom continues over roughly 6–8 weeks as the plant extends and branches. Self-pollination sets most of the seed, and the ripe pods discharge it explosively through early summer.

Detailed Descriptions

Foliage Description

green

Growing Conditions

Sun Requirements

SunPartial Shade SunFull Shade

Requires 2-6 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

Drainagemoist

Water & Climate

Water Needs

Medium

Care & Maintenance

Care Guide

Cardamine impatiens grows in part to full shade on moist, fertile woodland soils and tolerates deep shade that excludes many plants. It is not planted on purpose; management focuses on pulling plants before the pods ripen, since the seed scatters explosively once mature. Hand-pulling lifts the shallow-rooted plants easily, but it is timed before seed set to keep the seed from dispersing during removal. Repeated annual pulling is needed because the seed bank carries over. Removed plants with maturing pods are bagged rather than composted on site.

Pruning

No pruning is practiced on this weed. Plants are pulled or cut at the base before the pods ripen to prevent explosive seed dispersal. Material with formed pods is bagged and removed rather than left on the ground.