The Snail Vine - Confusion Reigns Supreme
The snail vine is an attractive vine and features a flower that bears a resemblance to a snail, hence the name. Beyond that, there is a great possibility for confusion and mistaken purchases if you are considering buying one, if indeed that is what you want. There are two scientific names associated with the snail vine, and you should be aware of both so you have a better idea of the plant you are getting. Unfortunately, the scientific names tend to be used interchangeably, so you may not be sure about your plant until it begins to grow.
One of the scientific names for the snail vine is Vigna caracalla. Caracalla is related to caracol, the Spanish name for a snail. Other sources indicate that caracalla is a take off of Caracas, the capital of Venezuela. As far as the plant is concerned, it makes little difference. The plant is also called the snail bean by some as it is a legume, and the beans are edible. The other scientific name is Phaselous caracalla. This species is also called a snail vine, snail flower, or Corkscrew flower. It is also a legume and bears a close resemblance to pole bean varieties.
Where Descriptive Names Fail - The four keywords are the two aforementioned scientific names, snail vine, and corkscrew plant, and this is where the fun begins. Even though the snail vine (V. caracalla) is sometimes advertised as having fragrant blooms, it does not. The flowers are very attractive, as are the vines themselves, but the flowers are not fragrant. The flowers of the corkscrew plant, P. caracalla, are fragrant. The snail vine in some locations can be very aggressive, especially since if the vines are allowed to touch the ground, and that can easily happen with a rapid grower, they will more often than not set roots. Once established, the snail vine can be difficult to get rid of, and in a tropical or very warm climate, can take over your yard, and your neighbors as well. The corkscrew plant is also a very rapid grower, but much better behaved and seldom becomes invasive. Troubles arise however when visiting the nursery. V. caracalla is often used as a synonym for P. caracalla, so it is very easy to take home what you think is a corkscrew flower and later find you have a flourishing snail vine in your back yard instead!
This makes it sound like the corkscrew plant is the good guy and the snail vine is the villain. Both plants have their adherents, and both plants have much going for them. The snail vine has exceptionally attractive foliage, and the only problem with the flowers is that they are not fragrant. The biggest complaint seems to be that when people buy a plant expecting fragrance, and don't get it, they are naturally a little upset.
Planting Directions - Let's assume that it is the snail vine you are (or think you have) purchasing. You can plant it from seed, or use stem or leaf cuttings, either in the ground, in a container, or in a hanging basket. Planted in the ground or in a container you can allow it to get huge. In a hanging basket it may have to be trimmed occasionally, but can grow to a length of 12' to 15' if allowed to. The snail vine prefers a mildly acidic soil, and should be planted in full sun. If planted from seed, expect sprouts to appear in 10 to 20 days. Plant near a wall or trellis, where the vines will have support, and space the plants one to two feet apart. This plant is hardy in USDA zone 9 through 11. It is not frost tolerant, but in these zones will reemerge the following spring after dying back at first frost.
If you are hesitant to purchase seeds because of the confusion surrounding the snail vine and corkscrew vine, your best bet might be to find someone who has the right plant, and maybe has photographs to prove it, who can share seeds or cuttings with you.