Macroptilium atropurpureum seeds Purple Bush-Bean Siratro

LATIN NAME: Macroptilium atropurpureum

COMMON NAME: Purple Bush-bean, Siratro

Siratro is a tough and generous legume of the tropics, and it has fed livestock across the warm world for generations. It grows as a climbing, twining perennial, with dense, green vines that scramble over the ground and up through grass and scrub, and in summer it is covered in clusters of deep purple, pea-like flowers, followed by slender pods. It is a plant of remarkable vigour, at home in the hot, humid tropics, and it fixes nitrogen through its roots, enriching the soil as it grows. It is one of the most important pasture legumes of the tropics, grown as forage for cattle and other livestock.

Siratro belongs to the pea family, Fabaceae, and it is native to the tropical and subtropical regions of the Americas, from Texas in the north to Peru and Brazil in the south. It has been introduced for use as forage to many tropical regions around the world.

Positive & Encouraging Seed Germination Guide

Growing siratro from seed is easy and very rewarding. The seeds sit inside the slender pods, and they have a hard coat, so soak them in hot water overnight, or nick them gently, before sowing. Sow them in pots of free-draining compost, about a centimetre deep, and keep them warm, bright and lightly moist. Germination usually begins within one to three weeks. Pot the seedlings on as they grow and plant them out in a warm, sunny, well-drained spot after all danger of frost. The plants grow vigorously, and within a season they will form a dense, flowering cover of nitrogen-rich growth.

Scientific Research & Plant Biotechnology

Siratro has a genuine and practical record in agricultural and pasture research. As one of the most important pasture legumes of the tropics, it has been studied extensively in forage and livestock research, and researchers have examined its growth, its yields, its nutritive value for cattle and its management in tropical pastures. Because it fixes nitrogen through its roots, it has also been studied in research on soil fertility and sustainable farming, where its value in enriching the soil and feeding livestock is well recognised. The plant has also been studied in agronomy for its cultivation in different tropical regions and its tolerance of grazing and poor soil. For a legume of such importance to tropical livestock, siratro has an exceptionally practical record of research.

Ecological & Economic Value & Wide Applications

Ecologically, siratro is a generous plant of the tropical pasture. Its purple flowers feed bees and other pollinators, and its nitrogen-fixing roots enrich the soil, improving poor, worn ground for the plants that follow.

Its economic value is considerable in the tropics. It is grown as forage for cattle and other livestock, valued for its vigorous growth, its nitrogen-fixing roots and its nutritive value, and it is also used to improve and restore pastureland, forming a dense, green cover that holds the soil and feeds the animals. For a grower, siratro is a valuable and dependable legume, and for a gardener it brings dense, flowering growth and better soil.

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.