Macroptilium atropurpureum

Macroptilium atropurpureum, commonly known as Purple Bush-Bean or Siratro, is a climber in the pea family (Fabaceae) native from Texas south to Peru and Brazil, and to the Caribbean, but widely naturalized in the tropics and subtropics, including Arizona, Florida, and Hawaii.

Description

The plant has a deep, fleshy taproot, the young stems are finely pubescent, and the leaves are trifoliate with ovoid leaflets having a few shallow lobes, and also slightly pubescent. The flowers are deep purple with a velvety sheen, reddish at the base, and have a typical pea flower shape. The long hirsute pods shatter when ripe. It is naturally diploid, 2n = 22.. M. lathyroides is a similar species, but has lanceolate leaflets that lack lobes and red to red-purple flowers.

Usage

Macroptilium atropurpureum is useful as a tropical forage crop in full sun, and can also be used to prevent soil erosion. It tolerates a wide range of soils and pH, and tolerates more salinity than other leguminous forage crops. It is well-adapted to drought by virtue of its taproot and pubescent leaves that reduce evaporation. Heavy frost causes dieback, but the plant resprouts from the crown in warmer conditions. M. atropurpureum cannot tolerate waterlogging.

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