Crotalaria

Crotalaria is a genus of flowering plants in the legume family Fabaceae, commonly known as rattlepods. The genus contains roughly 600 to 700 species of annuals, perennials, and shrubs, distributed mainly in tropical and subtropical regions of Africa, Asia, the Americas, and Oceania. They are employed in agriculture and horticulture in various warm-climate regions and are frequently found in disturbed habitats.

Most Crotalaria species have simple or pinnate leaves and produce bright yellow, pea-like flowers typical of many legumes. The fruits are pods that often contain several seeds; when mature, the pods can rattle, giving the plants their common name. Plant size ranges from low shrubs to erect herbaceous forms, and many species tolerate poor soils and dry conditions.

Ecology and uses: Crotalaria species form symbiotic relationships with nitrogen-fixing bacteria in root nodules, contributing to soil fertility. They are widely used as cover crops and green manures to protect soil, reduce erosion, and suppress weeds in warm climates. Some species are also grown as forage for livestock, notably Crotalaria juncea (sunn hemp). However, several species contain pyrrolizidine alkaloids, which can be hepatotoxic to livestock and humans if ingested in significant amounts.

Toxicity and regulation: due to their alkaloid content, management and species selection are important for safe use as forage or green manures. Some Crotalaria species have become invasive weeds in certain regions, underscoring the need for local assessment.

Etymology: the name derives from Greek krotalon, meaning a small club or rattle, in reference to the rattling seed pods.