Passiflora quadrangularis aka Grenadine

Passiflora quadrangularis is a vine known as giant granadilla. It grows in the tropics and keeps its leaves year-round. It belongs to Passifloraceae, the passionflower family. Kew places its native range from Colombia to Brazil. It grows on flood plains in tropical rainforests. Across the tropics, growers raise it for fruit and flowers. Its angled stems give it another name: square-stemmed passionflower.

This vine grows fast and grips nearby plants with tendrils. These coiled shoots are pale green and do not branch. Garden plants reach about 39–49 feet [12–15 metres] tall. They can spread to 5 feet [1.5 metres] wide. Some plants in Java have reached 148 feet [45 metres]. Large, broad, oval leaves cover the stems all year. The plant also forms fleshy tubers below the ground. It may take five to ten years to reach full size.

Scented flowers hang down from stems that bear leaves. Pale red petals frame purple and white threads called coronal filaments. Large yellow fruits follow and hold black seeds inside. Fruits can reach about 10–12 inches [0.25–0.30 metres] long. The pulp tastes mild and melon-like, with some tartness. People eat it fresh, cook it, or make drinks. They also cook young fruit and thick rind as vegetables. Sources note that people eat older plants’ roasted or baked roots. But the raw root is poisonous and strongly narcotic. Traditional medicine uses the roots, leaves, fruit, and rind. These uses do not show that home treatment is safe.

Grow it in rich soil that drains well but stays moist. It accepts acid, neutral, and alkaline soils. Outdoors, it needs shelter and a site free from frost. Sun or part shade suits it in warm spots. Under glass, give bright light but shade from hot sun. For pots, use a peat-free mix based on loam. Give plenty of water during growth, then less in winter. Keep the compost a little moist through that cooler rest. RHS advises a winter minimum of 13°C under glass. It lists UK hardiness H1A; PFAF lists USDA zones 10–12.

This vine suits warm courtyards, wall borders, and large pots. In colder places, it needs shelter indoors for winter. Growers can raise plants from seeds or semi-hardwood cuttings. They can also layer stems in spring or autumn. Under glass, red spider mites and scale insects may attack. Whiteflies may attack there too. Viral disease can occur, while honey fungus is rare.