Sigmoidotropis speciosa (Snail Vine)

Sigmoidotropis speciosa, commonly known as Purple Snail Vine or Snail Flower, is a vigorous perennial vine native to Mexico, Central America, and northern South America. Formerly classified as Vigna speciosa, it is now placed in the genus Sigmoidotropis. The plant climbs rapidly by twining stems and can quickly cover fences, trellises, pergolas, and other supports, making it an impressive ornamental vine in frost-free climates.

The unusual flowers are the defining feature of this species. Produced singly or in small clusters rather than large racemes, they are soft lavender to purple and have a strongly curved keel that resembles the shell of a snail, giving rise to the common names. Unlike the closely related Cochliasanthus caracalla, which is often confused with it in cultivation, the flowers of Sigmoidotropis speciosa are usually only faintly fragrant or scentless, are uniformly purple rather than multicolored, and are borne in much smaller clusters. It grows best in full sun to partial shade with fertile, well-drained soil and regular moisture during active growth. Suitable for USDA Zones 9-11, it can also be grown in large containers and overwintered indoors in colder climates. Under favorable conditions, this vigorous vine flowers over an extended season and quickly creates a lush tropical display.