Aeschynomene americana aka Joint Vetch

Aeschynomene americana belongs to the pea family, Fabaceae. It comes from tropical and subtropical parts of the Americas. Its range spans Mexico, Central America, and much of South America. It also extends through the Caribbean to Florida. The plant grows in both tropical and subtropical climates. Wild plants occur in damp places, including low coastal ground.

Its life span and shape vary with the local form. Some plants grow as annuals; others become small, short-lived shrubs. These shrub-like plants can live for two to four years. Most stems stand upright or rise from near ground level. Some plants grow almost flat against the ground. Plants reach about 1.6–6.6 feet [0.5–2 metres] tall. Their spread ranges from 3.3–8.2 feet [1–2.5 metres]. The source also lists a height of 4.9 feet [1.5 metres]. It reports that the species is self-fertile.

This plant grows best in full sun and warm conditions. Its preferred daytime range is 22–30°C. It can withstand brief light frosts, but harder frosts may kill it. It grows in gravel, sand, and clay, with finer soils more frequent. Low, wet sites with sandy soil also suit it. It prefers soil pH between 5.5 and 7. It can tolerate a wider range, from pH 4 to 8.

Moisture suits this species, though it withstands some dry spells. It tolerates flooded or waterlogged ground better than many warm-season legumes. Periods of waterlogging may even help its growth. In these conditions, nitrogen-forming nodules tend to develop near the stem base. Preferred annual rainfall lies between 1,000 and 1,500 millimetres. Farmers grow it as green manure, including for rice crops. It has become naturalized across many tropical areas. Some Pacific islands class it as invasive.

Seeds have a hard coat that can delay germination. Scarification and soaking can help water enter the seed. The source describes warm-water soaking for 12–24 hours. Seeds that remain firm may need a careful nick. This must avoid damage to the embryo inside. The source lists no known food or medicinal uses. It also lists no known hazards, but this does not establish edible use.