Pruning is an important part of caring for a healthy, vigorous Mandevilla vine. Prune it, then pinch it to encourage the Mandevilla to grow new stems and more flowers. Trim it back a little, just to neaten it up, or cut it way back to reduce its size and keep it in bounds.
Mandevillas (Mandevilla spp. syn. Dipladenia spp.), also known as pink allamandas, are tropical plants. They are hardy in U.S. Department of Agriculture plant hardiness zones 9 to 11. They may survive in USDA zone 8 gardens, although the stems will be killed back by freezing temperatures. In cooler climates, they are grown as annuals or planted in containers that are kept indoors during cold weather. These vines can reach heights of 10 to 20 feet, although they stay smaller when grown in containers. Their showy flowers appear in the summer and off and on throughout the year.
When to Prune
Prune a Mandevilla at the end of winter or beginning of spring before it begins to grow new stems. The flowers are produced on the current season's growth. Pruning them after they begin to grow can reduce that summer's flower buds.
What to Use
Use sharp, bypass hand pruners that have been sterilized with household disinfectant. Anvil-type pruners tend to crush Mandevilla stems rather than making a good, clean cut. Wash the pruners with hot, soapy water, then soak them in the disinfectant for a few minutes. Rinse them off with fresh water then dry them with a paper towel.
How to Prune
Reduce the plant to three to five of the strongest stems right after planting, or when there is only one stem, trim it back by one-third.
Prune old, thick stems off at ground level on an older Mandevilla. Trim away damaged stems or stems that appear diseased. Prune off overly long stems that are growing out away from the main vines, giving it a wild, unkempt look.
Trim up smaller Mandevillas that are being maintained in a shrubby shape by cutting back stems that are sticking out or dangling down toward the ground.
Pinch the growing tips off when the Mandevilla puts on a few inches of new stem length. This will encourage bushier growth with even more new stems, increasing the number of flowers produced during the summer.