Productive, prolific and easy to grow, morning glory vines (Ipomoea spp.) are the most popular of the annual climbing vines. Some species can reach lengths of up to 15 feet (4.5 m.), twining themselves around anything they can find. The flowers open in the morning and close in the afternoon, with masses of fresh blossoms opening each day. To keep these plants looking their best and well managed, some morning glory trimming may be necessary.
How to Prune Morning Glory
One of the most time consuming aspects of pruning morning glory vines is deadheading, or removing the spent flowers. When the flowers close in the afternoon, they will not open again and berries filled with seeds form in their place. Bringing the seeds to maturity drains a lot of energy from the vine and results in fewer flowers. Remove the spent flowers by squeezing them between your finger and thumbnail to keep the vines blooming freely.
Another important reason to deadhead morning glory vines is to keep them from becoming aggressive and weedy. When the berries mature, they fall to the ground and the seeds take root. Morning glory vines can take over the garden if left to reproduce at will.
When to Cut Morning Glories
As summer progresses, you might find that your morning glories need a lift. They may begin to look ragged or stop blooming as well as they should. You can revive the vines by cutting them back by one-third to one-half. This type of morning glory trimming is best done in summer. Remove damaged and diseased stems any time of year.
If you grow your own bedding plants from seeds, you’ll need to pinch them back while they are young. Pinch them when they have two sets of true leaves, removing the top one-half (1.25 cm.) to three-quarters (2 cm.) of an inch. Pinch out the tips of lateral stems when they develop. Pinching out the growth tips helps the vine develop a dense, bushy growth habit.
In USDA plant hardiness zones 10 and 11, morning glories will grow as perennials. In winter or early spring, cut back morning glory vines grown as perennials to about 6 inches (15 cm.) above the ground. This gets rid of old, tired growth and encourages them to come back strong and vigorous.