By: Darcy Larum, Landscape Designer
One might say that moonflower is morning glory’s counterpart. Ever the cheerful early bird of the garden, morning glory (Ipomoea purpureum) opens its stunning trumpet flowers with the first rays of the morning sun. Moonflower (Ipomoea alba), on the other hand, opens its lovely trumpet-shaped blooms at dusk, and are oftentimes the stars of evening moon gardens. Anyone who has grown moonflower, or their day-blooming cousin, has probably quickly learned that these vines need regular pruning to keep them in check and looking their best. Continue reading to learn how to prune a moonflower plant.
Moonflowers are beloved for their lightly, sweet scented, trumpet-shaped white to purple flowers, which bloom from dusk to dawn. Perennials only in warm climates of U.S. hardiness zones 10-12, moonflower vines are grown as annuals in cooler climates, where they have no trouble covering whatever structure you place them on.
With its rapid and rampant growth, gardeners who prefer a tidy, tame garden may find themselves trimming moonflower plants three times a year to control their shape and growth. Because it blooms on new wood, moonflower pruning can be done at several times of the year. Generally, however, moonflowers are cut back to the ground in autumn. The root zone of perennial moonflowers is then mulched for winter protection.
From autumn to early spring, annual moonflowers can be cut back or pulled out to make room for the next season’s plants. However, moonflowers have decorative seed pods which add interest to the garden in late summer through fall. Many gardeners choose to delay cutting back moonflowers to allow these decorative seeds to form. Seeds can then be harvested and stored to produce new moonflowers the following season.
Whenever pruning anything in the garden, only clean, sharp tools should be used to reduce the risk of disease. When pruning moonflower to shape, remove any crossing or crowding branches to open up the center to good air circulation and sunlight.
Also, cut back or retrain wild vines growing away from the trellis or support, or vines that have begun to trail along the ground or on other plants. When left unchecked, Ipomoea plants can choke out their companions.
If you enjoy trimming and training plants, moonflower is an excellent candidate to grow and train into a tree form or artistic espalier.
It is important to note that as a member of the nightshade group of plants, handling moonflower has caused skin irritations in some people. Always wear gardening gloves and wash hands frequently when handling moonflower plants.
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Why doesn't my well established moonflower plant have any blooms yet? It is thriving climbing a trellis in mostly full sun during the day.
If you've purchased a container-grown vine—standard nursery fare these days—no pruning is mandatory at planting time, especially with evergreen vines. But heading back, which will encourage new growth, may be a good idea if your plant has long, spindly shoots with few leaves or only a single stem. Bare-root plants should be headed back by no more than a quarter before they are planted to allow the vine to balance its growth below and above ground. Be sure to cut out any damaged or dead roots and stems, or stems that have minds of their own and appear determined to grow into the neighbor's yard rather than up your trellis.
Vines in their first or second year tend to sprout and elongate stems more than produce leaves and flowers. Pinching back shoot ends helps balance their growth. Also, woody vines tend to flower more generously on shoots that are horizontal rather than vertical, so keep that in mind as you direct and shape your climbers. Twining vines especially grow from upper buds and tend to lose their lower leaves. They may need severe heading back to promote foliage near the ground. If you want a compact vine, head back stems throughout the growing season if you want a vine to ramble, keep your pruning shears in their scabbard.
The guidelines for pruning mature vines are similar to those for pruning deciduous shrubs. Species grown for their foliage can be pruned throughout the garden season, but early spring before leaves appear puts the least stress on the plant. Vines that flower in summer and fall on the current year's growth, such as honeysuckles (Lonicera), should be pruned in late winter or early spring. That schedule gives the plant time to produce new shoots and flowers. Prune vines that flower early in the garden season on shoots produced the previous year—jasmines (Jasminum) and Wisteria are two—immediately after their flowers fade. Most hardy vines fall into this category.
Except. like all general rules, there are exceptions, the most important of which concerns vines that produce ornamental or edible fruits. Even if postflowering pruning is called for, wait until spring, or the fruit crop will be lost.
When you prune, be sure to do the following:
Pruning mature vines can be difficult, because their long stems become tangled. Don't be tempted to yank. Instead, prune one stem section at a time until you've cut out all you want to remove.
There are three types of gourds: hard-shell, ornamental and luffa. Pruning hard-shell, or Lagenaria, vines causes an increased quantity of fruit. To get the plant to produce more gourds, cut off the end of the primary vine when it is 10 to 15 feet long. Male flowers bloom on the primary vines, whereas female flowers bloom on secondary vines. Stopping the primary vine at 10 feet will allow more secondary vines to grow, which will make more gourds.
Locate the primary vine in May and June, when male flowers are blooming. Distinguish secondary vines from the primary vine by differentiating female flowers, which have ball-shaped miniature fruit swelling at the base, from male flowers. Keep track of the primary vine.
Examine the primary vine to make sure it is longer than 10 feet and has 16 to 20 leaves. Measure the length of the primary vine to 10 feet with a tape measure, starting at the base of the plant to the end of the vine. Note the point where the vine reaches 10 feet.
Locate the closest set of leaves near the 10-foot point. Prune the vine 1/4-inch above the set of leaves with pruning shears, trimming perpendicular to the vine. Dispose of the vine end in a compost pile or plastic trash bag.
Last Updated: March 19, 2020 References Approved
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Annual sunflowers (plants that only bloom once) typically do not need any pruning. However, sunflowers that are growing in groups may need to be trimmed to keep from knocking one another over. By comparison, perennial types of sunflowers will occasionally require a trim. Pruning helps these plants maintain a neat and tidy appearance during the summer months when they tend to get unruly. To prune your plants correctly, you will first have to know when to prune them.