Narrowleaf Bittercress - Cardamine impatiens

Description: Easily dispersed due to its seed shooting ability; can form dense stands, outcompeting native species.

Habit: Herbaceous annual or biennial with spreading leaves; grows up to 60 cm (2 ft) tall.

Leaves: Pinnately divided with numerous (6-20), sharply toothed leaflets; membrane-like, narrow, pointed auricles at the leaf base; basal leaves are arranged in a rosette and pinnately divided, 3-11 leaflets with rounded lobes.

Stems: Erect; glabrous.

Flowers: Small, white in color, up to 2.5 mm (0.1 in.) long, petals lacking or shorter than the sepals; bloom May through August.

Fruit and seeds: Slender seedpods (siliques) on spreading-ascending to erect pedicels, 1.5-2 cm (0.6-0.8 in.) long, 10-24 seeds, ripen from May to September.

Habitat: Established in Michigan; found on banks, along thicket margins, shady woods and on moist limestone rocks and cliffs.

Reproduction: By seeds expelled from siliques.

Similar species: Native sand bitter-cress (C. parviflora), Pennsylvania bitter-cress (C. pensylvanica), tansy-mustard (Descurainia pinnata) and common yellow-cress (Rorippa palustris) lack narrow-leaved bittercress? characteristic narrow, pointed auricle at the leaf base.

Monitoring and rapid response: Monitor moist forested sites in spring and summer; can be identified by its sagittate-auriculate leaf bases. Hand pull and remove all plants before seed dispersal. As this species has a limited distribution in Michigan, it is important to document new occurrences. Please obtain flowering or fruiting specimens with the diagnostic leaf bases and submit to: Anton Reznicek, Curator (Vascular Plants), University of Michigan Herbarium, 3600 Varsity Drive, Ann Arbor, MI 48108-2287.