Amorpha is a genus of plants in the pea family, Fabaceae. All the species are native to North America, from southern Canada, most of the United States (US), and northern Mexico. They are commonly known as false indigo. The name Amorpha means "deformed" or "without form" in Greek and was given because flowers of this genus only have one petal, unlike the usual "pea-shaped" flowers of the Faboideae subfamily. Amorpha is missing the wing and keel petals.

The desert false indigo or indigo bush (Amorpha fruticosa), is a shrub that grows from 3 m to 5 m tall. The species is considered a rare species in the US state of West Virginia and in the Canadian provinces of Manitoba and Ontario, but is considered an invasive plant in some areas of the northeastern and northwestern United States and in southeastern Canada, beyond its native range, and has also been introduced into Europe.

The lead plant (Amorpha canescens), a bushy shrub, is an important North American prairie legume. Lead plant is often associated with little bluestem (Schizachyrium scoparium), a common prairie grass. Native Americans used the dried leaves of lead plant for pipe smoking and tea.

Amorpha species are used as food plants by the larvae of some Lepidoptera species including Schinia lucens, which feeds exclusively on the genus.

Amorphol, a rotenoid bioside, can be isolated from plants of the genus Amorpha.

Species

Amorpha comprises the following species:

thumb|right|Flowers of [[Amorpha fruticosa]]

<!-- Amorpha angustifolia was reclassified as Amorpha fruticosa. -->

  • Amorpha apiculata <small>Wiggins</small>

<!-- Amorpha arizonica was reclassified as Amorpha fruticosa. -->

<!-- Amorpha brachycarpa was reclassified as Amorpha canescens. -->

<!-- Amorpha bushii was reclassified as Amorpha fruticosa. -->

  • Amorpha californica <small>Torr. & A. Gray</small>—California false indigo, mock locust
  • var. californica <small>Torr. & A. Gray</small>
  • var. napensis <small>Jeps.</small>
  • Amorpha canescens <small>Pursh</small>—leadplant
  • Amorpha confusa <small>(Wilbur) S.C.K. Straub, Sorrie & Weakley</small>
  • Amorpha crenulata <small>Rydb.</small> (endangered)

<!-- Amorpha croceolanata was reclassified as Amorpha fruticosa. -->

<!-- Amorpha curtissii was reclassified as Amorpha fruticosa. -->

<!-- Amorpha cyanostachya was reclassified as Amorpha herbacea. -->

<!-- Amorpha densiflora was reclassified as Amorpha schwerinii. -->

<!-- Amorpha dewinkeleri was reclassified as Amorpha fruticosa. -->

<!-- Amorpha elata was reclassified as Amorpha fruticosa. -->

<!-- Amorpha emarginata was reclassified as Amorpha fruticosa. -->

<!-- Amorpha floridana was reclassified as Amorpha herbacea. -->

<!-- Amorpha fragrans was reclassified as Amorpha fruticosa. -->

  • Amorpha fruticosa <small>L.</small>—desert false indigo
  • Amorpha georgiana <small>Wilbur</small>—Georgia false indigo
  • Amorpha glabra <small>Desf. ex Pers.</small>—mountain false indigo

<!-- Amorpha glandulosa was reclassified as Dalea cliffortiana. -->

  • Amorpha herbacea <small>Walter</small>—clusterspike false indigo
  • var. herbacea <small>Walter</small>
  • var. floridana <small>(Rydb.) Wilbur</small>

<!-- Amorpha hispidula was reclassified as Amorpha californica. -->

<!-- Amorpha humilis was reclassified as Amorpha fruticosa. -->

  • Amorpha laevigata <small>Nutt.</small>—smooth false indigo

<!-- Amorpha microphylla was reclassified as Amorpha nana. -->

<!-- Amorpha montana was reclassified as Amorpha glabra. -->

  • Amorpha nana <small>Nutt.</small>—dwarf false indigo
  • Amorpha nitens <small>Boynton</small>—shining false indigo

<!-- Amorpha occidentalis was reclassified as Amorpha fruticosa. -->

  • Amorpha ouachitensis <small>Wilbur</small>—Ouachita false indigo

<!-- Amorpha ovalis was reclassified as Indigofera sphaerocarpa. -->

  • Amorpha paniculata <small>Torr. & A.Gray</small>—panicled false indigo

<!-- Amorpha pendula was reclassified as Amorpha fruticosa. -->

<!-- Amorpha pubescens was reclassified as Amorpha herbacea. -->

<!-- Amorpha pumila was reclassified as Amorpha herbacea. -->

<!-- Amorpha punctata was reclassified as Amorpha nana. -->

  • Amorpha roemeriana <small>Scheele</small>—Roemer's false indigo
  • Amorpha schwerinii <small>C.K. Schneid.</small>—Schwerin's false indigo

<!-- Amorpha subglabra was reclassified as Amorpha roemeriana. -->

<!-- Amorpha tennessensis is a misspelling of Amorpha tennesseensis, which was reclassified as Amorpha fruticosa. -->

<!-- Amorpha tennesseensis was reclassified as Amorpha fruticosa. -->

<!-- Amorpha texana was reclassified as Amorpha roemeriana. -->

<!-- Amorpha virgata was reclassified as Amorpha fruticosa. -->

Species names with uncertain taxonomic status

The status of the following species is unresolved: