- Name also: Spring Pea, Spring Vetchling
- Family: Pea Family – Fabaceae (Leguminosae)
- Growing form: Perennial herb.
- Height: 20–40 cm (8–15 in.). Stem erect, bristly, wingless, almost glabrous.
- Flower: Corolla zygomorphic, initially purple, later bluish, 13–20 mm (0.52–0.8 in.) long, nodding, fused at base. Petals 5; the upstanding the ‘standard’, the lateral two the ‘wings’, the lower two united to form the ‘keel’, overall shape of corolla being butterfly-like. Calyx 5-lobed. Stamens 10. A single carpel. Inflorescence an axillary, long-stalked, nodding-flowered and often one-sided, 3–10-flowered raceme.
- Leaves: Alternate, stipulate. Blade pinnate, 2–4-pairs, lacking tendrils. Leaflets ovate, tapered, with entire margins, thin, glabrous. Stipules large, wide.
- Fruit: 40–60 mm (1.6–2.4 in.) long, glabrous, blackish brown, 8–14-seeded, opening pod (legume).
- Habitat: Broad-leaved forests, young forests.
- Flowering time: May–June.
Several of the erect genus Lathyrus species which lack tendrils were earlier classified in their own genus. Spring vetch’s seeds are poisonous: they contain amino acids which cause bloating, pain, infection and in the worst case paralysis. Its flowers on the other hand are popular for vases and at least in densely populated areas whole populations can get picked. It is a demanding species and it grows wild in Finland sporadically and locally: favourable habitats are rare. For this reason the flowers should not be picked but rather left to bloom where they are growing.
Spring vetch is the only one of its genus to flower early, often blooming already in May – although the inflorescence only peaks at the beginning of summer. Unlike many other early spring flowers, e.g. wood anemone and genus Gagea plants, spring vetch doesn’t wither immediately after its flowering time: rather it gets denser throughout the whole summer and the stem is at its most impressive only when summer is turning into autumn.
Spring vetch can be differentiated from its rarer close relatives bitter vetch (L. linifolius) and black pea (L. niger) by its widely ovate leaflets (bitter vetch’s leaflets are lanceolate–linear, black pea’s lanceolate).