Senna hirsuta aka Woolly Senna

Senna hirsuta is part of the pea family, Fabaceae. Its older name is Cassia hirsuta. It is native to tropical and subtropical parts of the Americas. Its range starts in Mexico and reaches Argentina. This range spans Central America and the Caribbean. Kew lists it as a perennial or shrub. A perennial lives for more than two years. The species takes different forms across its range.

This plant grows fast and may stand upright or spread. Its spread can be loose in form. It may have one stem or several stems. Young growth is soft, but stems turn woody with age. The plant has a strong, bad smell. Its listed height is about 6.6 feet [2 metres]. A fuller account gives a top height of 8.2 feet [2.5 metres]. In Southeast Asia, it can bloom in every month. People pick its seedpods while young for food.

It grows in tropical and subtropical regions. It grows best in full sun. Records place it up to 2,300 feet [700 metres] above sea level. Its native climate has a dry season. In Southeast Asia, it grows on plains and hills. It grows on waste ground, roadsides, and rail banks. It also grows in dry ditches, gardens, and fields. Other sites include secondary forest, where trees have grown back. Plants regrow well after coppicing: cutting them near ground level. Reports differ on whether its roots host nitrogen-fixing bacteria. These bacteria make nitrogen from the air usable by plants. Its use as green manure does not resolve this doubt.

People gather wild plants for food and medicine. Some grow it as a green manure crop. People use leaves and young pods in cooked vegetable dishes. They also add them to salads. More time spent cooking helps lessen their bad smell. People roast the seeds to make a coffee substitute. Fresh seeds have toxalbumin, a toxic protein. The source says that roasting destroys this protein. This warning matters when using the plant for food. The seeds yield a gum that dissolves in water. They do not yield it in commercial amounts.

Traditional medicine uses leaves for kidney problems and herpes. People apply leaf mixes to skin problems and cracked nipples. They use root mixes as tonics and rubs for rheumatic pain. These uses do not prove that treatments work or are safe. Its main known growing problem is escape from planted sites. It has become a weed in Southeast Asia and the Pacific. Take note of this record before planting in similar climates.