- Name also: Beach Pea, Circumpolar Pea, Sea Vetchling
- Latin synonym: Lathyrus maritimus ssp. japonicus
- Family: Pea Family – Fabaceae (Leguminosae)
- Growing form: Perennial herb.
- Height: 10–60 cm (4–25 in.). Stem usually limp, wingless, densely haired–glabrous.
- Flower: Corolla zygomorphic, initially purple, later bluish, 14–20 mm (0.56–0.8 in.) long, 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, wings white. Calyx 5-lobed. Stamens 10. A single carpel. Inflorescence a long-stalked, 5–12-flowered raceme.
- Leaves: Alternate, fairly stalkless, stipulate. Blade pinnate, 3–5-pairs, terminal leaflet modified into a tendril. Leaflets elliptic, with entire margins, quite juicy, bluish-green. Stipules large, wide.
- Fruit: 30–50 mm (1.2–2 in.) long, brown pod (legume).
- Habitat: Sandy and stony sea-shores.
- Flowering time: July–August.
Many people regard sea pea, with its bluish grey leaves and large flower, as being the most ornamental of the species that grow in Finland. This beauty is only enhanced in the wild: the likeliest place to find it is on sandy and gravelly sea-shores, where it grows as a pioneer some distance from the water line, just out of reach of the waves. Sea pea typically grows in half-open places and can hold its own for quite a long time amidst encroaching vegetation, even on the edge of forests.
At first glance the colour of sea pea’s stems and its general presence can bring pea plants to mind, and Carl von Linné himself made a mistake when he named it Pisum maritimum. The species’ pods and seeds are larger than many of its relatives’, and they have been used in years of crop failure as human food. Legumes are very nutritious for humans because they are high in protein, and peas, lentils, broad beans and French beans are all common food in Finland along with many others, e.g. soya beans, which grow in warmer climates. The plant itself intended the protein to be used by the maturing shoot rather than humans. Non-toxic, cultivated stands are the result of careful cross-breeding, and the seeds of wild pea plants should not be eaten: unprocessed sea pea seeds are poisonous.
Sea pea is divided into two subspecies, of which ssp. maritimus grows in Finland. This is further divided into three variations, with densely short-haired var. pubescens growing around the Gulf of Bothnia, glabrous var. maritimus growing on the southern coast, and small, rare var. acutifolius growing on the Gulf of Finland.