Red Darling-pea

Swainsona plagiotropis is a prostrate or ascending perennial herb, that typically grows to a height of up to 15 cm (5.9 in) and sometimes has hairy stems. Its leaves are imparipinnate, mostly 50–120 mm (2.0–4.7 in) long with 13 to 25 narrowly elliptic or narrowly egg-shaped leaflets with the narrower end towards the base, the side leaflets 10–17 mm (0.39–0.67 in) long and 1–4 mm (0.039–0.157 in) wide with broadly egg-shaped stipules mostly 5–9 mm (0.20–0.35 in) long at the base of the petioles. The flowers are reddish-purple, arranged in racemes of 2 to 5, the flowers 10–15 mm (0.39–0.59 in) long, on a hairy pedicel about 3 mm (0.12 in) long. The sepals are joined at the base to form a tube about 2.5 mm (0.098 in) long, with lobes longer than the tube. The standard petal is 12–15 mm (0.47–0.59 in) long and 10–20 mm (0.39–0.79 in) wide, the wings about 8–10 mm (0.31–0.39 in) long and the keel about 9–10 mm (0.35–0.39 in) long and 4–5 mm (0.16–0.20 in) deep. Flowering occurs from August to November, and the fruit is an oval to oblong pod 15–25 mm (0.59–0.98 in) long and 8–10 mm (0.31–0.39 in) long, with the remains of the strongly curved style 8–9 mm (0.31–0.35 in) long.

Red swainson-pea grows in grassland, often in table drains in the west of New South Wales and a few places in north-central Victoria, mostly along the upper Murray River.