Indigo-bush amorpha is a native, perennial shrub found in Texas and throughout the western United States and Mexico. It grows in calcareous [chalky] limestone soils and is strongly associated with riparian areas, as it is usually found on a stream bank or on the waters’ edge.
Shrub-like with many stems that form large clumps.
Grows 3 to 9 feet tall.
Has smooth gray to brown bark on younger plants that can become rough and scaly on older plants.
Has leaves that are odd-pinnately compound, 3 to 10 inches long with 9 to 27 leaflets. The dull green leaflets vary from oval to oblong with pointed or rounded tips.
Produces a small legume pod that will have one to two brown, shiny seeds 1/8-inch in length.
The flowers of this shrub grow on erect spikes that are 2 to 6 inches long, clustered in two or more with dark blue to reddish-purple color. Each flower has only one petal. The name “amorpha” means without form, referring to the solitary petal of the flower.
Indigo-bush amorpha has been reported to be very poisonous to cattle but plants are rarely utilized by livestock. It is fair browse for whitetail deer and many birds use the small seeds as a food source.
Indigo-bush amorpha is a highly desirable riparian shrub because it is one of the best species for stabilization of stream banks.
Editor’s note: Kent Ferguson, retired rangeland management specialist from USDA Natural Resources Conservation Service (NRCS), is providing us with plant identification photo stories to help ranchers identify those forbs, forages and species growing in the pastures. Additional photos provided by USDA NRCS.