Swainsona


Swainsona is a genus of about 85 species of flowering plants in the family Fabaceae, and is endemic to Australia. Plants in this genus are herbs or subshrubs with imparipinnate leaves and usually purple flowers similar to others in the family.

Description

Plants in the genus Swainsona are prostrate to erect annual or perennial herbs or subshrubs, often with many stems at the base. The leaves are usually imparipinnate with a few to many leaflets, with stipules at the base of the petiole. A few to many flowers are borne in a raceme in leaf axils on an erect peduncle with bracts at the base, and small bracteoles at the base of the sepals. The sepals are joined at the base to form a bell-shaped tube with 5 equal lobes, or the upper 2 lobes shorter. The petals are mostly purple, sometimes white, pink, yellow orange or red. The standard petal is kidney-shaped to more or less round, usually longer than the wings and often longer than the keel. There are ten stamens, nine of which are joined with each other and the tenth free and facing the standard petal.

Taxonomy

The genus Swainsona was first formally described in 1806 by Richard Anthony Salisbury in Paradisus Londinensis and the first species he described was Swainsona coronillifolia,, this species is most closely related to the New Zealand genera Montigena, Clianthus, and Carmichaelia. The genus name honours the English botanist Isaac Swainson.
A few species are known to produce swainsonine, a phytotoxin harmful to livestock. In Australia, animals intoxicated with swainsonine are said to be pea struck.

Species list

The following is a list of species of Swainsona accepted by Plants of the World Online as of 10 September 2023:

Distribution

Species of Swainsona are found in all six Australian states and in the Northern Territory and Australian Capital Territory.