Hi. Phaseolus caracalla is the non fragrant Snail vine, Vigna caracalla is the fragrant Corkscrew vine. The foliage is the same but the blooms are very different. I've wintered both over with no problem. I used to keep them inside with HID lights but now I keep the stems cut back to a few inches and keep them in the greenhouse. Here's an old post that shows pics of both. Top is Snail, bottom Corkscrew. As you can see this has been confusing for a long time. lol BTW Corkscrew vine seeds are larger and rounder.

Here is a link that might be useful: Snail vs Corkscrew vines

Karen, thank you. This has been bugging me since I bought the seed, now I just have to wait for the flower to open, make sure it is the scented corkscrew vine Vigna caracalla :).

Annette

Vigna caracalla is by definition the same plant as Phaseolus caracalla is the same plant as Cochliasanthus caracalla, the flower in the picture labeled as corkscrew vine. I don't know the identity of the picture labeled (incorrectly , that name should also refer to same plant as corkscrew vine) as 'snail vine' but I can promise you, its name does not contain the word 'caracalla.'

The other 'snail vine may be Vigna speciosa, which is the same as Phaseolus speciosa and the same as Sigmoidotropis speciosa

Here is a link that might be useful: Vigna speciosa

Not sure what the Lavender/Purple Form is called since they have apparently changed the names
Could be Vigna speciosa

Or possibly
phaseolus adenanthus

But probably
phaseolus giganteus

Someone simply needs to study the Purple Form, but for sure the Fragrant Snail Vine/Corkscrew Vine is
Vigna caracalla

Synonym/Previously called: Phaseolus caracalla
Which means that Phaseolus caracalla is the out-dated name and Vigna caracalla is the current and correct name for the fragrant vine

The New World members of Vigna (except the ones with yellow flowers) have just been separated out into several smaller genera. They are genetically closer to Phaseolus than to Vigna.

Here is a link that might be useful: Abstract

There is no listing in IPNI or Tropicos for Phaseolus gigantea; not a real name.
Leptospron (Phaseolus) adenanthum has the spiral of its keel perpendicular to the banner petal. Sigmoidotropis speciosa has the keel twisted, and then coiled in the same plane as the banner.