Chamaecrista rotundifolia Seeds | Roundleaf Sensitive Pea

Green foliage of Roundleaf Sensitive Pea (Chamaecrista rotundifolia) with paired round leaflets and small yellow flowers — Roundleaf Sensitive Pea (*Chamaecrista rotundifolia*): Fabaceae, a low perennial pasture legume from tropical America, now widely sown in northern Australia.

LATIN NAME: Chamaecrista rotundifolia

COMMON NAME: Roundleaf Sensitive Pea

Plant Profile

Roundleaf Sensitive Pea is a low, spreading perennial of the pea family, native to tropical America and now naturalised across the wet tropics and subtropics. It forms a mat thirty to sixty centimetres high, with paired round leaflets that fold together within seconds of being touched, the same sensitive reflex that gives the plant its name. Bright yellow flowers open in small clusters through the warm months.

It thrives on open, sunny ground and tolerates acid, infertile soils that defeat most other legumes, which is why it has become a standard pasture plant in Queensland. Bees work the flowers steadily, and the flat pods ripen and shatter seed onto the soil, letting the stand thicken on its own. Two forms are recognised in the trade: the typical round-leafed plant and a narrower-leafed variant, and stands usually mix the two where seed has been saved for generations.

Science & Biotechnology

The leaf-folding response, triggered by touch within a second or two, makes the species a convenient laboratory subject for studies of rapid plant movement alongside its famous cousin <em>Mimosa pudica</em>. Botanists have also used the genus to trace how the cassia group of legumes split from the rest of the family.

The cultivar Wynn, released in Queensland in the 1980s, was selected for persistence on infertile acid soils, and agronomic trials across northern Australia have shown it holding on for years after sowing with no fertiliser, regenerating each season from its own shed seed. Grazing trials in Queensland measured liveweight gains on Wynn-based pastures among the best recorded for unfertilised legume swards in the region, which secured its place in the state’s sowing recommendations.

Uses & Benefits

Its main work is agricultural: as a self-regenerating pasture legume it fixes nitrogen, lifts the protein content of grass swards and carries stock through the dry season on country where nothing else holds. Orchardists use it as a low, walkable groundcover that suppresses weeds and feeds the soil.

In the garden it is a cheerful curiosity for a sunny bed, its folding leaves delighting children, its flowers pulling in bees all summer. These small sennas share the family’s anthraquinone chemistry and folk laxative records, though they are grown mainly as ornamentals and forage. Because it holds green leaves through drought better than most tropical legumes, it is also valued as a stand-over feed that carries stock through the late dry season.

Growing from Seed

The hard seed coat needs a scratch or a brief pour of near-boiling water before sowing; untreated seed may sit for weeks. Sow in spring once the soil has warmed, on the surface of a loose mix or directly into a prepared bed in full sun, covering no more than a few millimetres.

Keep the bed moist until the seedlings are up, then let the soil dry between waterings, since the plant resents waterlogging. It nodulates freely with native rhizobia and needs no fertiliser; a phosphate-poor, acid soil suits it as well as a rich one. Seedling vigour is good: the first true leaves open within a fortnight, and the plants close over the row within two months of a spring sowing.

Our Take

A quiet, sunny legume that folds its leaves when touched and improves the soil as it goes. Give it warmth, drainage and room to spread, and it keeps itself going for years.

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