Macroptilium lathyroides Seeds | Phasey Bean
LATIN NAME: Macroptilium lathyroides
COMMON NAME: Phasey Bean
Plant Profile
Phasey Bean is a fast, semi-erect annual legume from tropical America, with slender twining stems, three broad leaflets and small red-purple pea flowers scattered along the shoots. It can stand nearly a metre tall in a season, or scramble through a support if one is given.
It was carried around the warm world as a forage plant and has naturalised widely, so it now turns up as a wayside plant through the tropics. In the garden or on the farm it is a quick source of leafy growth, and it fixes nitrogen through its root nodules like its pasture relatives. Flowering begins six to eight weeks after sowing and continues while the plant grows, so buds, flowers and young pods share a stem for most of the season.
Science & Biotechnology
It belongs to the phasey bean group of tropical pasture legumes, distinguished from its relative siratro by its almost hairless leaves and its upright habit. The seed is hard-coated, which in the wild staggers germination across seasons and is the reason farmers scarify before sowing.
Because it completes its life cycle in a single season, it is used as a short-rotation legume where perennial pasture legumes fail in the dry tropics. It nodulates freely with the cowpea-group rhizobia already present in most tropical soils, so it rarely needs inoculant, a practical advantage over the clovers. Its seed yield is high for a forage legume, which is one reason it reappears unasked wherever it has been grown.
Uses & Benefits
Its main use is forage: it is grazed, cut for hay or made into silage, and it responds to cutting by regrowing from the base. In gardens it serves as a fast green manure or a filler crop on newly broken ground, feeding the soil as it grows.
It is also a fine plant for observing the pea family at work: nodules on the roots, self-setting flowers and a pod that twists as it dries. Its hay cuts at forty to fifty days, and a second regrowth follows within a month in the wet season. Because it stands acid, infertile soil that defeats white clover, it is the legume smallholders in the humid tropics reach for first, and it bridges the gap between crops on newly cleared land.
Growing from Seed
Scarify the seed by rubbing it between two sheets of sandpaper, or pour hot water over it and sow after an overnight soak.
Sow a centimetre deep in warm soil or a free-draining mix at 22 to 25 °C; germination takes under a week in warmth.
Give the plants full sun and ordinary soil, and cut or graze them before they set seed if they are being used as green manure. Where it is grown for seed rather than green manure, leave the stand until the pods rattle, then cut and dry it under cover, since shattering in the field is heavy.
Our Take
A one-season tropical legume that earns its space as forage, green manure and a working demonstration of the pea family’s machinery.
Related Reading
Gardeners who grow Phasey Bean often pair it with these related subjects: