Cochliasanthus caracalla aka Snail Vine

Cochliasanthus caracalla climbs and belongs to the pea family, Fabaceae. It is native from Mexico through tropical South America. The climate there is tropical, with a dry season. Its names include snail vine, corkscrew flower, and snail bean. Older sources call it Vigna caracalla. RHS lists that name as a synonym, or another name. This perennial vine lives for more than one year. It stays evergreen in places that have no frost.

The stems twist around supports as the vine grows. Garden vines reach 12–20 feet [3.7–6.1 metres]. Some reach 30 feet [9.1 metres]. Plants can spread to about 6 feet [1.83 metres]. Growth is fast. It can grow 20 feet [6.1 metres] in one growing season. Each green leaf has three leaflets in a palmate pattern. They spread from one point, like fingers on a hand. Each leaflet is 0.25–0.42 feet [0.08–0.13 metres] long. A trellis, arbor, fence, or wall gives it climbing space.

The flowers twist into tight shapes like a snail shell. They open white, then turn a deeper pink-purple with age. Some blooms have cream or yellow marks as well. Each flower can reach about 0.17 feet [0.05 metres] long. The upright flower clusters, called racemes, reach 1 foot [0.3 metres]. The blooms have a strong scent. Chicago Botanic Garden likens it to the scent of hyacinths. Flowers bloom from July through October, or until the first autumn frost. Birds and butterflies visit the plant.

Grow this vine in full sun and rich, moist soil. The soil must drain well and not hold standing water. Chicago Botanic Garden notes that it needs moderate fertilizer use. Missouri Botanical Garden gives USDA zones 9–12 as its hardiness range. Chicago Botanic Garden gives a narrower range: zones 9–10. Outside warm climates, gardeners can grow it as an annual. They can also grow it in a pot indoors for winter. Give it a sunny window through the winter months.

The vine brings scented summer blooms to tall garden supports. Chicago Botanic Garden lists it for beds and borders, too. Missouri Botanical Garden says it needs little care. It also says the vine grows with ease from seed. Once it fills its space, trim the leaves and tendrils. This can spur more blooms. The same source reports no major insect or disease problems. Yet in warm tropical places, it can spread strongly from its own seeds. Take this into account where winters do not check its growth.