Citation: Salisb., Parad. Lond. t. 28 (1806).

Derivation: After Isaac Swainson, who died in 1806; he maintained a private botanical garden at Twickenham, near London, about the year 1789.

Synonymy: Not Applicable

Common name: (A. Lee (1948) Contr. N.S.W. Natn. Herb. 1:131-271 .) Swainsonas, Darling peas.

Description:
Herbaceous sometimes shrub-like annuals or perennials decumbent or procumbent, occasionally erect herbs, with single or few stems, pubescent with hairs basifixed or laterally attached or (symmetrically) medifixed to glabrescent; leaves imparipinnate, stipulate.

Inflorescence a few- to many-flowered axillary raceme on an erect peduncle, usually exceeding the leaves, the lower part of the peduncle usually long and naked; bracteoles affixed on the pedicel just below the calyx, often minute; calyx campanulate, with 5 subequal teeth, pubescent or glabrous outside; teeth usually pubescent inside; flowers purple, bluish, red, pinkish, brown or yellow; standard suborbicular or reniform, green and white above the claw, often with 2 raised calli or with some ornamentation in this region; wings not often distinctive in shape, often auriculate, nearly as long as the standard; keel often upturned or incurved at the apex, straight, turned sideways or spirally coiled, obtuse, acute or somewhat beaked, often pouched on each side above the claw; 9 stamens united in a sheath slit open on the upper side of the ovary; 10th stamen facing the standard, free; end of the fused filaments alternately longer and shorter; anthers equal; ovary sessile or stipitate, pubescent or glabrous, usually many-ovulate; style incurved or following the keel shape so variously flexed or straight, bearded adaxially along the edge; stigma terminal, small, tip straight, inflexed, incurved, hooked, coiled, recurved or geniculate, with or without hairs behind the stigma.

Pod globular or cylindrical, straight or curved, with the upper suture ridged or intruded, sometimes inflated, walls hard or membranous, usually sharply beaked by the hard persistent part of the style, seed exarillate.

Image source: fig. 327 in J.P. Jessop and H.R. Toelken Ed. 1986. Flora of South Australia (4th edn).

Distribution:  About 60 species endemic in Australia, 1 endemic in New Zealand and 1 in North America. Occurs all over Australia, especially in inland areas where rainfall is low, but absent from south-western W.Aust. where the rainfall exceeds 500 mm.

Biology: No text

Taxonomic notes: Pubescence in the key is applicable to the stem and leaves only.

Key to Species:

1. Plant leafless; stems rigid; flowers yellow, 8-10 mm long	S. rigida 23.
1. Plant with leaves
2. Ovary glabrous
3. Flowers 15-20 mm long; standard with plate-like calli; (pod 25-50 x 8-20 mm)
4. Calyx glabrous (except for the ciliate margins); pod subsessile, lunate	S. colutoides 6.
4. Calyx densely white-woolly-pubescent; pod stipitate, straight- oblong	S. greyana 10.
3. Flowers 4-14 mm long; standard ecallose (or with minute folds or calli in S. dictyocarpa)
5. Calyx glabrous outside; style-tip straight or slightly inflexed
6. Style-tip without a hair-tuft behind the stigma; standard with minute folds or calli	S. dictyocarpa 7.
6. Style with a tuft of hairs behind the stigma; standard ecallose
7. Flowers 4-7 mm long, purple; pod globular, to 10 mm long; leaflets 21-41	S. microphylla 5.
7. Flowers 9-14 mm long, yellow; pod compressed, 10-15 mm long; leaflets 11-19
8. Calyx glabrous inside (including teeth); stipules broad, leafy	S. laxa 11.
8. Calyx teeth pubescent inside and ciliate; stipules narrow-deltoid	S. rigida 23.
5. Calyx pubescent
9. Style-tip without a hair-tuft behind the stigma, slightly geniculate; leaflets 5-13	S. viridis 29.
9. Style-tip with a tuft of hair behind the stigma, truncate or incurved
10. Style-tip truncate; flowers 4-7 mm long, violet-blue to purple; leaf with 21 or more leaflets; pod globular	S. microphylla 15.
10. Style-tip incurved; flowers 9-15 mm long, yellow; leaflets 13-15; pod compressed	S. rigida 23.
2. Ovary hoary or pubescent (all over or in part)
11. Style with a hair-tuft behind the stigma as well as the usual ventral beard
12. Leaflets 1 or 3	S. unifoliata 27.
12. Leaflets 5 or more
13. Flowers 4-7 mm long; style incurved
14. Racemes 6-15-flowered; flowers 5-7mm long; standard with calli	S. microcalyx 14.
14. Racemes l-3-flowered; flowers 4-5 mm long; standard ecallose
15. Leaflets 9-13; peduncle awned; pod fusiform	S. oliveri 8.
15. Leaflets 5-7; peduncle not awned; pod oblong, obtuse	S. leeana 12.
13. Flowers 7-12 mm long; style-tip straight to inflexed or geniculate; pubescences 1 of rather long loosely appressed to spreading hairs
16. Hairs (of stems and leaves) medifixed, the pubescence dense, silvery; style slender, tip slightly inflexed; hair-tuft behind the stigma not always conspicuous; standard ecallose	S. tephrotricha 26.
16. Hairs basifixed; hair-tuft behind the stigma apparently a part of an oblique ring
17. Style-tip geniculate; standard with 2 callosities; stipules narrow, entire, 4-7 mm long	S. flavicarinata 9.
17. Style-tip straight to inflexed; standard ecallose
18. Plant villous; leaflets obovate, 5-15 mm long; stipules broad, leafy	S. villosa 28.
18. Plant glabrescent; leaflets lanceolate, 10-15 mm long; stipules lanceolate	S. campylantha 4.
11. Style-tip without any hair-tuft behind the stigma, but only the usual ventral beard
19. Keel spirally coiled or distinctly twisted sideways
20. Hairs of pubescence basifixed or laterally attached at the base; style slender (long), coiled; flowers 8-15 mm long
21. Keel spirally twisted in a complete circle, tip yellow, recurved onto or past the lower part of the keel, with 2 distinct folds near the claw; pubescence of appressed flattened short white hairs	S. procumbens 22.
21. Keel twisted in an incomplete spiral, sometimes forming an S-shape or C-shape, tip blue without folds; pubescence of loosely appressed fine curved hairs	S. swainsonioides 25.
20. Hairs of pubescence medifixed; style rigid and dilated basally (slender in S. phacoides); leaflets 5-13
22. Flowers 10-15 mm long, brownish to red, drying purple; stipules 5-10 mm long
23. Hairs of pubescence cylindrical, often wrinkled (medifixed hairs mixed with basifixed and/or laterally asymmetrically attached); standard claw straight; style slender, bearded evenly, with a straight tip; leafletsusually 5-7 (sometimes to 21 or more)	S. phacoides 21.
23. Hairs of pubescence flattened (only medifixed); standard oblique to the keel by the sideways twisted claw; style rigid, bearded more distally; leaflets 7-13	S. stipularis 24.
22. Flowers 6-10 mm long, red, pink or purple; stipules 2-8 mm long
24. Style (evenly bearded) tip minutely inflexed; leaflets 7-13 (mostly acute); stipules 4-8 mm long; peduncle glabrescent, 5-9-flowered; flowers 8-10 mm long, reddish; standard with 2 distinct and thickened lines above the straight claw; wings straight; keel with pouches; hairs fusiform-cylindric on the leaves	S. fissimontana 8.
24. Style-tip straight or hooked; leaflets 5-9; stipules 2-5 mm; peduncle pubescent, 5-20-flowered; flowers 6-9 mm long, pink or purple; hairs flattened on the leaves.
25. Style-tip straight; leaflets (7-9) obtuse to retuse, often with a terminal (yellowish) gland; flowers 6-7 mm long, purple or pink; wing straight; keel with pouches	S. microcalyx 14.
25. Style-tip minutely and sharply hooked; leaflets (5-9) acute; flowers 7-9 mm long, pink; wings geniculate with the auricles ciliate or not; keel with or without a pair of folds	S. murrayana 17.
19. Keel straight or somewhat obscurely twisted sideways
26. Calyx glabrous except along the veins, teeth subulate; leaflets 5-9, broad; flowers c. 12 mm long, 3-7 per raceme; calli present on the standard; hairs basifixed, laterally attached S. oligophylla 18
26. Calyx pubescence dense or sparse (rarely absent), not confined to the veins; calyx teeth triangular-lanceolate or short and acuminate
27. Hairs of pubescence (asymmetrically) medifixed
28. Keel without pouches or folds; standard ecallose; flowers 7-9 mm long; style-tip geniculate	S. oroboides 20.
28. Keel with pouches or folds; standard with or without calli
29. Flowers 4-7 mm long (pinkish to purple); style rigid, tip straight to minutely inflexed or hooked; standard ecallose; lateral leaflets acute or retuse when with a terminal gland
30. Flowers 6-7 mm long, 6-15 per raceme; style-tip straight	S. microcalyx 14.
30. Flowers 4-5 mm long, 3-7 per raceme; style-tip hooked to coiled	S. minutiflora 16.
29. Flowers 10-15 mm long; style-tip various
31. Stipules finally scarious, 1-7 mm long; flowers few to 10, condensed terminally; style slender, cylindrical, evenly bearded to the straight tip; hairs cylindrical, often crinkled	S. phacoides 21.
31. Stipules leafy, to 10 mm long; flowers 5-20, loosely spaced on the distal third of the peduncle; style rigid, flattened basally, bearded in the distal half, tip various; hairs flattened; keel sometimes obscurely twisted sideways	S. stipularis 24.
27. Hairs of the pubescence basifixed or laterally attached at the base (if asymmetrically medifixed, then the pod with a rigid, not intruded, suture in some specimens of S. lessertiifolia); flowers 7-9 mm long
32. Style-tip incurred to coiled; hairs long, soft, spreading or thick and appressed when usually sparse at maturity
33. Leaflets to 31; racemes to 50-flowered; calyx densely villous; pod globose; stems more than 3 mm thick basally, densely and shortly tomentose	S. burkittii 2.
33. Leaflets 5-15; racemes 5-15- or 25-35-flowered; calyx densely woolly or sparsely pubescent; pod cylindrical, 10-30 mm long
34. Stems more than 3 mm thick basally; racemes 25-35- flowered; flowers evenly spaced; calyx and pod densely woolly-pubescent	S. canescens 5.
34. Stems less than 3 mm thick basally; racemes 5-15-flowered; calyx and pod sparsely pubescent
35. Calyx pubescent, teeth longer than the tube; leaflets tomentose below; pubescence of soft villous spreading hairs	S. burkei subsp. acuticarinata 1.
35. Calyx glabrous, teeth shorter than the tube; leaflets glabrescent below; pubescence of short flattened appressed hairs	S. campylantha 4.
32. Style-tip straight, inflexed or geniculate
36. Style-tip geniculate; leaflets usually pubescent above; calyx usually with white or pale hairs	S. oroboides 20.
36. Style-tip straight or inflexed; leaflets almost glabrous above; calyx usually with dark hairs
37. Leaflets 5-9, mostly linear, 1-2 mm wide; style-tip inflexed	S. campestris 3.
37. Leaflets 13-19, mostly elliptic, 2-9 (usually 4-7) mm wide; style-tip straight or minutely inflexed	S. lessertiifolia 13.

Author: Not yet available