False Indigo

Amorpha fruticosa

Invader Images

    • False Indigo Flowers
      False Indigo Flowers
    • False Indigo
      False Indigo
    • False Indigo Infestation
      False Indigo Infestation

Common Look-alikes

    • Bristly Locust- Only look like false indigo when they are young
      Bristly Locust- Only look like false indigo when they are young

Identification

Appearance

Indigobush (Amorpha fruticosa) is a shrub that can grow as tall as 20 ft. high and its width is typically twice its height. The branches are firm and woody and the twigs are green and hairy. The flowers are terminal on the branches in erect racemes. The fruit is about 1/4 inch long, curved, with resinous dots and contains two seeds each.

Foliage

Alternate, pinnately compound, to 10 inches long, 13 to 35 leaflets per leaf, each leaflet elliptical with an entire margin and on a petiole, 1 to 2 inches long, dull green above and light green below, usually glabrous, a slender stipule is present with young leaves.

Flowers

Borne on tall (up to 6 inches), slender spikes at the ends of the twigs, deep purple-blue with long bright orange or yellow anthers, appearing mid-summer, opening from base to tip.

Fruit

Best described as tiny cucumbers, bright green and drying to brown, from 1/4 to 1/2 inch long.

Biology

This is considered a watch list species.

Ecological Threat

Amorpha fruticosa can tolerate nutritionally poor soils, most notably because of its association with nitrogen fixing bacteria. It also makes a good highway shrub because of its tolerance for salt. It has the potential to crowd out native species, especially along waterways above the high water level.

Origin

Native to southwestern states

Habitat

Edge, wetland, lake or pond, open disturbed area, river or stream, roadside, yard or garden. In New England, Amorpha fruticosa is typically found along riverbanks, flood plains, tidal zones and other areas associated with water. It can occasionally be found in moist open woods. It is also found planted along highways in some sections of southern New England.

Citations

Photo Credit

5446428, 5446436, 5446432, Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

5395945, Robert Vidéki, Doronicum Kft., Bugwood.org

Information Credit 

Invasive Plant Atlas of New England

Virginia Tech 

Department of Ecology State of Washington