Lathyrus tuberosus aka Earth Chestnut

Lathyrus tuberosus is a perennial vine in the pea family, Fabaceae. Gardeners also call it tuberous pea or earth-nut pea. Its native range spans Europe, Siberia, Iran and Algeria. It grows in temperate regions and is not native to Britain or Ireland. Wild plants grow in crop fields and hedges. It has tuberous roots and loses its green leaves each year.

The stems climb or scramble through nearby plants. Garden plants reach about 5–8 feet [1.5–2.5 metres] tall. The RHS describes a height near 6.6 feet [2 metres]. Their spread reaches about 1.6 feet [0.5 metres]. Flowers range from deep pink to crimson and appear in summer. The blooms suit cutting for indoor use. This vine fits cottage gardens, beds and borders beside walls. It also suits sunny woodland edges and lightly shaded hedges. Its flowers add colour, and the plant attracts wildlife. It also fixes nitrogen.

Give it fertile soil with plenty of humus and good drainage. Keep the soil moist without leaving it waterlogged. Full sun suits it, though light, dappled shade also works. The RHS lists clay, loam, sand and chalk as suitable soils. It accepts acid, neutral or alkaline conditions in cultivation. PFAF notes that wild plants avoid acid soils. The RHS gives a UK hardiness rating of H3. This means it suits mild or coastal parts of Britain. PFAF lists USDA zones 5–9, a different hardiness assessment.

Before planting, work well-rotted manure into the soil. During growth, the RHS advises balanced liquid feed every two weeks. Remove spent blooms and cut stems back after flowering. Raise plants from seed in a cold frame during early autumn or spring. Seeds can also go straight outside in mid-spring. Watch for aphids, slugs and snails. Powdery mildew, Fusarium wilt and sweet pea viruses may cause problems.

The cooked tubers are edible, with a sweet, starchy taste. Their flavour recalls sweet potato. PFAF rates them highly for food but reports low yields. They offer an occasional crop rather than a staple food. Do not treat the whole plant as edible. The RHS warns that pods and seeds are unsuitable for people and pets. It also advises gloves and protective clothing when handling plants. PFAF reports no known medicinal uses.