Senna hirsuta


Senna hirsuta, commonly known as woolly senna, is a species of flowering plant in the family Fabaceae and is native to Central and South America, but is naturalised in many other countries. It is an erect or spreading shrub or herbaceous perennial with pinnate leaves, with two to six pairs of egg-shaped leaflets, and yellow flowers arranged in groups of two to six, with six fertile stamens and four staminodes in each flower.

Description

Senna hirsuta is an erect or spreading shrub or herbaceous perennial that typically grows to a height of up to. Its leaves are pinnate, long on a petiole long, usually with two to six pairs of egg-shaped leaflets, sometimes with the narrower end towards the base. The leaflets are long and wide, usually spaced apart. There is a sessile gland at the base of the petiole. The flowers are yellow and arranged on the ends of branches and in upper leaf axils in groups of two to five on a peduncle about long, each flower on a pedicel long. The petals are long and there are six fertile stamens, the anthers long and of different lengths, as well as four staminodes. Flowering occurs in most months, and the fruit is a flattened cylindrical Glossary of [plant morphology#Fruit types|pod] long, wide and curved.

Taxonomy and naming

This species was first formally described in 1753 by Carl Linnaeus who gave it the name Cassia hirsuta in Species Plantarum. In 1979, Howard Samuel Irwin and Rupert Charles Barneby transferred the species to the genus Senna as S. hirsuta in the journal Phytologia. The specific epithet means "hairy".
In the same journal, Irwin and Barneby described seven varieties of S. hirsuta, and the names are accepted by Plants of [the World Online]:Senna hirsuta var. acuminata H.S.Irwin & Barneby Senna hirsuta var. glaberrima H.S.Irwin & Barneby Senna hirsuta var. hirsutaSenna hirsuta var. hirta H.S.Irwin & Barneby Senna hirsuta var. leptocarpa H.S.Irwin & Barneby Senna hirsuta var. puberula H.S.Irwin & BarnebySenna hirsuta var. streptocarpa H.S.Irwin & Barneby

Distribution

Senna hirsuta is native to most countries in South America, to Nicaragua, Honduras and Cuba in Central America, and to Arizona, New Mexico, Mexico and Puerto Rico in North America. It is also naturalised in countries in Africa, South Asia, Southeast Asia and in Queensland in Australia.
Variety acuminata is only found in south-east Brazil, var. glaberrima to Arizona and New Mexico, and var. leptocarpa is native to southeast Brazil, Colombia and Paraguay