Swainsona Explained

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 (pinnate, with a terminal leaflet) 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.^{[1] [2] [3]}

Taxonomy

The genus Swainsona was first formally described in 1806 by Richard Anthony Salisbury in Paradisus Londinensis and the first species he described (the type species) was Swainsona coronillifolia, (now accepted as a synonym of Swainsona galegifolia.^{[4] [5] [6]}

A member of the family Fabaceae (legumes), this species is most closely related to the New Zealand genera Montigena (scree pea), Clianthus (kakabeak), and Carmichaelia (New Zealand broom).^[7] The genus name (Swainsona) honours the English botanist Isaac Swainson.^[8]

A few species are known to produce swainsonine, a phytotoxin harmful to livestock (see Locoweed). In Australia, animals intoxicated with swainsonine are said to be pea struck.^[9]

Species list

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

• Swainsona acuticarinata (N.T., S.A., W.A.)
• Swainsona adenophylla – violet swainson-pea, violet Darling pea (S.A., N.S.W., Vic.)
• Swainsona affinis – common poison pea (W.A., S.A., N.T., Qld, N.S.W.)
• Swainsona beasleyana (W.A.)
• Swainsona behriana – Behr's swainsona (N.S.W., S.A., Vic.)
• Swainsona brachycarpa – slender swainson-pea (N.S.W., Qld., Vic.)
• Swainsona bracteata (N.S.W., Qld.)
• Swainsona burkei (N.T., Qld.)
• Swainsona burkittii – woolly Darling pea (S.A., N.S.W.)
• Swainsona cadellii (N.S.W.)
• Swainsona calcicola (W.A.)
• Swainsona campestris (S.A., W.A.)
• Swainsona campylantha – Gilgai Darling pea (Qld., N.T., S.A., N.S.W., W.A.)
• Swainsona canescens – grey swainsona (Qld., S.A., W.A.)
• Swainsona colutoides – bladder senna, bladder vetch (W.A., N.T., S.A., N.S.W.)
• Swainsona complanata (W.A.)
• Swainsona cornuta (W.A.)
• Swainsona cyclocarpa (W.A., N.T.)
• Swainsona decurrens (W.A.)
• Swainsona dictyocarpa (S.A.)
• Swainsona disjuncta (W.A., S.A., N.T.)
• Swainsona ecallosa (W.A.)
• Swainsona elegans (W.A.)
• Swainsona elegantoides (W.A.)
• Swainsona eremaea (S.A.)
• Swainsona extrajacens (S.A., N.S.W.)
• Swainsona fissimontana (S.A., N.S.W.)
• Swainsona flavicarinata (W.A., N.T., S.A., Qld., N.S.W.)
• Swainsona formosa – Sturt's desert pea or Sturt pea (W.A., N.T., S.A., Qld., N.S.W.)
• Swainsona forrestii (W.A.)
• Swainsona fraseri (N.S.W., Qld.)
• Swainsona fuscoviridis (S.A.)
• Swainsona galegifolia – smooth Darling pea (N.S.W., Qld., Vic.)
• Swainsona gracilis (W.A.)
• Swainsona greyana – Darling pea, hairy-Darling pea (S.A., N.S.W., Vic.)
• Swainsona halophila (W.A.)
• Swainsona incei (W.A.)
• Swainsona katjarra – Birriliburu swainsona (W.A.)
• Swainsona kingii (W.A., S.A.)
• Swainsona laciniata (W.A., N.T.)
• Swainsona laxa – skeleton pea, yellow swainson-pea, yellow Darling pea, sandhill swainsona (N.S.W., S.A., N.T., Qld.)
• Swainsona leeana (W.A., S.A.)
• Swainsona lessertiifolia – coast swainson-pea, bog pea, Darling pea poison pea, poison vetch (S.A., Vic., Tas.)
• Swainsona longicarinata (W.A.)
• Swainsona longipilosa (W.A.)
• Swainsona luteola – dwarf Darling-pea (N.S.W., Qld)
• Swainsona maccullochiana – Ashburton pea (W.A.)
• Swainsona microcalyx – wild violet (S.A., W.A.)
• Swainsona microphylla – small-leaf swainson-pea, small-leaf swainsona, poison swainson-pea (W.A., N.T., S.A., Qld., N.S.W., Vic.)
• Swainsona minutiflora (S.A.)
• Swainsona monticola – notched Swainson-pea (N.S.W., A.C.T.)
• Swainsona murrayana – slender Darling-pea, slender Darling pea (N.S.W., Vic., Qld., S.A.)
• Swainsona oligophylla (N.T., S.A., Qld., N.S.W.)
• Swainsona oliveri (W.A., N.T., S.A., N.S.W.)
• Swainsona oroboides – variable swainsona, kneed Darling pea (W.A., N.T., S.A., Qld., N.S.W.)
• Swainsona paradoxa (W.A.)
• Swainsona parviflora (Qld., N.S.W.)
• Swainsona paucifoliolata (W.A.)
• Swainsona pedunculata (W.A.)
• Swainsona perlonga (W.A.)
• Swainsona phacoides – dwarf Swainson-pea, lilac Darling pea (N.S.W., Vic., S.A., W.A., N.T., Qld.)
• Swainsona plagiotropis – red swainsona-pea (N.S.W., Vic.)
• Swainsona procumbens – Broughton pea, swamp pea (N.S.W., Vic., Qld.)
• Swainsona pterostylis (W.A.)
• Swainsona purpurea – purple Swainson-pea, purple Darling pea (W.A., S.A., N.T., Qld., N.S.W.)
• Swainsona pyrophila – yellow Swainson-pea, yellow Darling pea (S.A., Vic., N.S.W.)
• Swainsona queenslandica – smooth Darling pea (Qld., N.S.W.)
• Swainsona recta – mountain Swainson-pea, small purple pea (N.S.W., Vic.)
• Swainsona reticulata – kneed Swainson-pea (S.A., N.S.W., Vic., Qld.)
• Swainsona rostellata (W.A.)
• Swainsona rostrata (N.T., S.A.)
• Swainsona rotunda (W.A.)
• Swainsona sejuncta (Qld.)
• Swainsona sericea – silky Swainson-pea, silky pea (N.S.W., Vic., S.A.)
• Swainsona similis (N.S.W., Qld.)
• Swainsona stenodonta (W.A.)
• Swainsona stipularis (N.S.W., S.A., Qld., Vic.)
• Swainsona swainsonioides – downy Swainson-pea, downy Darling pea (N.S.W., S.A., Qld., Vic.)
• Swainsona tanamiensis (W.A., N.T.)
• Swainsona tenuis (W.A., S.A., N.T.)
• Swainsona tephrotricha (S.A.)
• Swainsona thompsoniana (W.A.)
• Swainsona unifoliolata (W.A., N.T., S.A.)
• Swainsona vestita (S.A.)
• Swainsona villosa (W.A., N.T., S.A.)
• Swainsona viridis – creeping Darling pea (N.S.W., S.A.)

Distribution

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

Notes and References

1. Web site: Thompson . Joy . James . Teresa A. . Swainsona . Royal Botanic Garden Sydney . 10 September 2023.
2. Web site: Swainsona . State Herbrium of South Australia . 10 September 2023.
3. Web site: Jeanes . Jeff A. . Stajsic . Val . Swainsona . Royal Botanic Gardens Victoria . 10 September 2023.
4. Web site: Swainsona . Australian Plant Name Index . 10 September 2023.
5. Book: Salisbury . Richard A. . Paradisus Londinensis . 1806 . William Hooker . London . 28 . 10 September 2023.
6. Web site: Swainsona coronillifolia . Plants of the World Online . 10 September 2023.
7. Wagstaff . Steven J. . Peter B. Heenan . Michael J. Sanderson . 1999 . Classification, origins, and patterns of diversification in New Zealand Carmichaelia (Fabaceae) . American Journal of Botany . 86 . 9 . 1346–1356. 10.2307/2656781 . 2656781 . American Journal of Botany, Vol. 86, No. 9 . 10487821. free .
8. Book: Sharr . Francis Aubi . George . Alex . Western Australian Plant Names and Their Meanings . 2019 . Four Gables Press . Kardinya, WA . 9780958034180 . 116 . 3rd.
9. News: THE DARLING PEA. . . 14 May 1897 . 16 May 2014 . 5 . National Library of Australia.