Vigna caracalla, a tropical, flowering vine that thrives in U.S. Department of Agriculture plant hardiness zones 9 through 11, earned the common name "snail vine" for its spiraled flowers that resemble a snail shell. The flowers, which bloom from midsummer into early fall, are white when they first appear, but slowly change to pink and finally lavender when fully opened. The vines climb structures through the use of twining stems and can grow up to 20 feet long. Without regular pruning, vines can become tangled and unattractive with old and dead stems.
1 Clean and disinfect bypass pruners in a 10 percent solution of 1 part chlorine bleach and 9 parts water. This prevents you from spreading disease from a previously pruned plant to your snail vine. Repeat the disinfection process each time you cut through diseased stems.
2 Cut all dead, diseased and damaged vines back to the point of origin on the parent branch or to a healthy leaf set. Cut diseased stems at least 6 inches outside the affected area to ensure you remove all the disease. Remove these types of stems throughout the year as soon as you notice them.
3 Prune back long, unruly vines to a healthy leaf set to control the size and maintain shape; remove no more than one-third of a vine's total length at one time. Cut these vines after the plant finishes flowering in early fall if you live in a frost-free zone.
4 Thin out as many as one-third of the total vine stems after flowering if the plant becomes tangled and crowded. Cut these stems back to the ground or intersection with a parent stem. Cut tangled, weak vines first, and slowly unravel them to avoid damaging the remaining vine.
5 Cut old wood and weak stems to within 8 inches of the ground in early fall after flowering to encourage new, stronger growth.
6 Cut the entire plant back to within 8 inches of the ground if the plant suffers frost damage in a frost-prone zone. Leave the dead plant material on the plant until the danger of frost has passed. Mulch the ground around the stems well for insulation. If the temperatures weren't below freezing for an extended period, causing a hard freeze, the vine might sprout new growth. Toss the dead vines in a compost pile to decompose.