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Bastard Indigo Amorpha fruticosa


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Bastard Indigo - flower and leaf
credit: Dalgial/CCSA

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Alternate name: Indigo-bush, False Indigo-bush

Family: Fabaceae, Pea view all from this family

Description This glandular, thornless shrub is distinguished by its leaves with 11-27 leaflets, its dense spikes of small, deep purple flowers, and its curved, glandular pods about 1/3 inch long.
Habit: native and introduced, perennial shrub; deciduous; airy, spreading, leggy; erect, much-branched stems; may form dense colonies.
Height: 3-17 ft (0.9-5.1 m).
Leaf: alternate, dull green, pinnately compound, 4-12 in (10-30 cm) long; 9-27 leaflets, oblong to elliptic, spine-tipped, to 2 in (5 cm) long and 1 in (2.5 cm) wide.
Flower: purple to dark blue, with one petal, 0.25 in (6 mm) long, and 10 protruding yellow stamens; held in crowded terminal spike, 3-8 in (7.5-20 cm) long.
Fruit: small pod, curved, 0.3 in (8 mm) long.

Flower April to July.

Flower May (in south); June - July (in north)

Habitat Moist: wet meadows, stream banks, shore lines, ditches, floodplains, wet woods; also cultivated as an ornamental.

Range Native to the southeast and plains states, naturalized to the north and west; now found from Manitoba to Quebec, and throughout the lower 48 states, except for Nevada and Montana.

Discussion Also called desert false indigo, false indigo, bastard indigobush, indigobush. Considered weedy or invasive in many locations; listed as invasive or noxious in Connecticut and Washington.

Comments Pruning of lower branches results in a nicely-shaped, small tree. Nutrient-poor soil restricts legginess and enhances floral display. This very flood tolerant species is effective for erosion control along waterways. It spreads easily and can become weedy. Like other members of the pea family, this plant requires the presense of microorganisms which inhabit nodules on the plant's root system and produce nitrogen compounds necessary for the plant's survival. Soil/seed inoculum is available at most native plant nurseries.

Exposure Preference Sun to shade.

Native Distribution New Jersey to s.e. Wisconsin, Minnesota, Saskatchewan & Wyoming, s. to Florida, Texas & n. Mexico,S. California to New Mexico & adjacent Mexico

Site Preference Stream & pond edges; open woods; roadsides, canyons

Soil Preference Moist soils to dry sands. pH adaptable.