- Family: Pea Family – Fabaceae (Leguminosae)
- Growing form: Perennial herb. Rootstock thin. Subterraneous runners long, creeping, branched.
- Height: 30–60 cm (12–25 in.). Stem quite erect–ascending, almost glabrous.
- Flower: Corolla zygomorphic, purple, 12–15 mm (0.48–0.6 in.) long, Petals 5; the upstanding the light-coloured ‘standard’, the lateral two the ‘wings’, the lower two united to form the ‘keel’, overall shape of corolla being butterfly-like. Stamens 10, filaments with fused bases. A single carpel. Inflorescence a very short-stalked, 2–5 flowered raceme.
- Leaves: Alternate, stalked, stipulate. Blade pinnate, 4–8-pairs, terminal leaflet modified into a tendril. Leaflets widely–narrowly ovate, with entire margins. Stipules untoothed, dotted.
- Fruit: 20–30 mm (0.8–1.2 in.) long, slightly hairy, becoming glabrous as it ripens, dark brown–black pod (legume).
- Habitat: Meadows, banks, waste ground, forest margins, young forests, broad-leaved forests, shores.
- Flowering time: June–August.
Bush vetch grows on young meadows and banks, often next to fences. It usually uses its prehensile organs, i.e. tendrils, to support its limp stem on other plants. Bush vetch’s stem is sturdy and can stay erect on its own when it has to. Its nectaries in the stipules have a very interesting structure. On many plants the nectaries are only in the flowers, and as such meant only as a reward for pollinators, but the nectaries at the base of bush vetch’s leaves attract mainly sweet-toothed ants. These do not directly help the plant’s pollination, but apparently they act as bodyguards, keeping flightless robbers away from the flowers and attacking leaf-munching grubs – lively ants can even make larger mammals think twice about eating the plant. The nectar also attracts pollinators, but it spreads more efficiently vegetatively rather than by seed. The plant can develop criss-crossing, abundantly branched subterraneous runners that are up to 6 metres (20 feet) long and have roots up to 1 metre (3.3 feet) deep.
Bush vetch is comprised of two subspecies, of which ssp. montana is more common in Finland, and ssp. sepium quite rare. Bush vetch is reminiscent of common vetch (V. sativa), which can sometimes be found in cultivated fields and yards, on waste ground and beside roads, but the latter has sharp-pointed leaflets.