2n = 18

Small to large tree, often up to 25 m high, with 1 main trunk or several prominent main branches; main branches upright to spreading. Divaricating and/or strongly flexuose juvenile branchlets absent; branchlets densely pubescent, becoming glabrous with age; hairs appressed, spreading or patent, predominantly curly, curved, or twisted, also straight. Seedlings and juveniles moderately to densely leafy, leaves with increasing numbers of leaflets. Leaflets on juveniles 6.0-9.0 × 3.5-6.0 mm, ovate, ± orbicular to elliptic, glabrous to sparsely pubescent, becoming moderately pubescent, not crowded or overlapping. Leaves on adults up to 17 cm long, imparipinnate, petioles and rachides channelled above, leaflets 47-75. Leaflets on adults 2.0-8.0 × 2.0-5.0 mm, ovate to broadly elliptic, sometimes ± orbicular, distal leaflets usually smaller than proximal leaflets, sometimes crowded but not overlapping, adaxial surface grey to green-grey, abaxial surface lighter than adaxial surface and often concave; apices usually retuse to sometimes rounded; bases obtuse; petiolules up to 2 mm long, often only up to 0.5 mm long on leaflets < 3 mm long; petioles, rachides, petiolules, and leaflets usually pilose, sometimes villous, hairs 0.2-0.6 mm long, appressed, decumbent, spreading or patent, predominantly curly, curved, or twisted, but also straight. Inflorescences racemose, with up to 7 flowers; peduncle and rachis 20-40 mm long; pedicels up to 20 mm long, each subtended by a bract; bracts 1.5-3.5 mm long; peduncles, rachides, pedicels, bracts, and calyces moderately to densely pubescent; hairs brown appressed, decumbent, spreading, or patent. Calyx 9-13 × 10-16 mm, cupulate, rim shallowly lobed, with deeper notch adjacent to standard. Corolla yellow; keel petal blade 34-50 × 9- 14 mm, wing petal blade 25-48 × 6-9 mm, standard petal blade 20-35 × 11-21 mm; petals with distinct claws, 5.0-6.5 mm long. Stipe 6-1 1 mm long, ± glabrous. Ovary 17-23 mm long, densely pubescent; hairs 0.4-0.7 mm long, off-white to light brown, appressed, spreading or patent, straight, curved, or twisted. Style 12-14 mm long, exerted beyond anthers, glabrous or with a few twisted hairs. Stigma fringed with short hairs. Filaments 25-40 mm long; anthers 1.8-2.0 × 0.9-1.0 mm. Fruit 60-120 mm long, 4-winged, brown, sparsely to moderately pubescent, with up to 11 seeds. Seeds 5-8 × 4-5 mm, oblong, yellow to yellow-brown. FL Oct-Dec; FT Jan-May.

A S. microphylla ramificatione juvenili non divaricata, foliis cinereis et foliolis pluris late ellipticis vel orbiculatis pilis eofum appressis vel effusis arcuatis torsivisque, et in habitatione in arenosaxo, limosaxo et calcareo substrato differt.