Common Name: False Indigo

General Information

Amorpha fruticosa is a deciduous shrub that produces a clump of branched stems up to 4 metres tall from a rhizomatous rootstock[, ].
The plant is harvested from the wild for local use as a dye and insecticide. It is used in shelterbelts and soil stabilization projects and is also grown as an ornamental.
The plant has escaped from cultivation in some areas and is known to be invasive in southern and eastern Europe, possibly also in other areas. It can form extensive stands due to its dense growth habit, altering the vegetation structure and replacing native species[].

Known Hazards

The plant is said to contain alkaloids and be poisonous to livestock[].

Botanical References

, ,

Range

N. America - Manitoba to Quebec, south through central and eastern N. America to northern Mexico, Texas and Florida. Naturalized further west.

Habitat

River banks, rich moist thickets, floodplain forests etc[, , ]. Grows chiefly in limestone soils[].

Properties

Weed Potential	Yes
Edibility Rating
Other Uses Rating
Habit	Deciduous Shrub
Height	2.50 m
Growth Rate	Medium
Pollinators	Insects
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Amorpha fruticosa is a very hardy plant, tolerating temperatures down to about -25°c when fully dormant. It is also very adaptable, being found from the cold continental climate of northern USA to the semi-arid subtropics of northern Mexico[, , ].
Prefers a light well-drained sandy soil in sun or light shade[, ]. Plants are fairly wind-resistant[].
A polymorphic species, there are many named forms[]. The flowers have a vanilla perfume[].
Plants resent root disturbance, they should be planted out into their final positions whilst small[].
Trees only ripen their seed in fine autumns[].
Plants are said to be immune to insect pests[].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[].

Edible Uses

The crushed fruit is used as a condiment[, , ].

Medicinal

None known

Agroforestry Uses:

Plants have an extensive root system and are also fairly wind tolerant, they can be planted as a windbreak and also to prevent soil erosion[, ].
Amorpha fruticosa is a fast-growing plant, able to grow on poor soils, that can fix atmospheric nitrogen and build up humus levels and fertility in the soil. When growing in areas polluted by heavy metals it has been shown to concentrate several of these metals in its tissues. It has a high potential for use in phytoremediation projects, either as a means of removing these metals or as a means of locking them up and helping to restore the fertility of the soil[].

Other Uses

Resinous pustules on the plant contain 'amorpha', a contact and stomachic insecticide that also acts as an insect repellent[, , ].

The stems are used as bedding[].

The plant contains some indigo pigment and can be used to make a blue dye[, ]. Unfortunately, the pigment is only present in very small quantities, there is not enough to harvest commercially[].

Propagation

Seed - pre-soak for 12 hours in warm water and then sow early spring in a greenhouse[, ]. The seed usually germinates in 1 - 2 months at 20°c[]. When large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse for their first winter. Plant them out in late spring or early summer, after the last expected frosts.
Cuttings of half-ripe wood, early summer/July in a frame. High percentage[].
Cuttings of mature wood of the current seasons growth, autumn, in a sheltered position outdoors. Takes 12 months[].
Suckers in spring just before new growth begins[].
Layering in spring .