How to Grow Morning Glory (Ipomoea)

With spectacular trumpet-shaped flowers up to 6 inches in diameter, morning glories (Ipomoea spp.) are most frequently grown as annuals, though they can be perennial in U.S. Department of Agriculture plant hardiness zones ranging from 8 to 12. Their heart- or ivy-shaped 4 to 6-inch leaves decorate twining vines which can climb to 20 feet or more. Morning glory blooms usually close by noon on sunny days, but frequently will remain open longer on overcast ones. Easy to grow, the plants can become invasive in almost any climate due to their heavy self-seeding.

Most of the intricately patterned morning glories, including tie-dyes and those with white edges or spatters such as "Chocolate" or "Blue Silk," are Ipomoea nil -- also known as Ipomoea imperialis -- types (USDA zones 9 through 12). They produce flowers up to 6 inches in diameter and are often known as Japanese morning glories. Ipomoea tricolor varieties (USDA zones 8 through 12), including the familiar "Heavenly Blue," can almost match them in size with flowers up to 5 inches wide. The blooms of Ipomoea purpurea types (USDA zones 9 through 11), such as those of the purple "Grandpa Ott’s" heirloom, generally don’t surpass 2 1/2 to 3 inches in size. However, their vines often flower earlier and more prolifically than those of larger species. Because morning glories sometimes don't bloom until 10 to 14 weeks after their seeds are planted, gardeners in cold climates frequently sow them indoors four to six weeks before the last frost date in spring.

The vines should be planted in full sun, preferably near an east-facing fence or trellis where they will catch the morning’s first rays. They prefer light, well-drained, mildly acidic to mildly alkaline soil of only medium fertility, since overly rich or constantly moist ground can cause morning glories to make lots of lush foliage but few blooms. Space the seedlings from 6 to 12 inches apart and the same distance from their support. The vines usually can twine their way up a fence or trellis. If you are growing them against a smooth wall, however, you will need to provide strings or netting to which they can attach themselves.

Morning glory vines planted in the ground generally don’t need fertilizer and shouldn’t have it either, as it will incline them to make too many leaves and not enough flowers. Keep the soil around the plants lightly moist until they are well-established. Once they are growing well, gradually reduce the amount of water you give them, but not to the point that the vines wilt.

If you don’t have in-ground space for morning glories, you can grow them in pots instead, provided that you have a very sunny windowsill or patio on which to position those containers. For the best results, fill 6-inch pots with a mix of one part potting soil, one part peat moss and one part sand. Plant two to three morning glories in each pot next to plant stakes or a pot trellis. As potted morning glories have less soil from which to derive their nutrients, you may need to fertilize them once every two weeks by adding 1/2 teaspoon of a bloom booster type plant food such as 15-30-15 to 1 gallon of water.