Shine on, silvery moonvine

Flower & Garden Magazine, Feb-March, 1985 by Marjia Bahr

Gardeners are missing something special if they don't grow the moonvine. Few vines produce flowers as spectacular. Moonflowers resemble enormous white morning glories, but no morning glory can equal their dazzling, alabaster purity.

Blooms begin opening as the sun goes down. Long, elegant buds quickly unfurl into six-inch flowers with petals like white silk. The blooms emit a honeysuckle-like scent that draws pollinating insects to them in the dark.

Moonvine and morning glory both belong to the same family, Convolvulaceae. The vines look alike, and have similar growth habits, but moonvines are larger plants than morning glories. Both have flowers that last only one day, but their blooming habits are strikingly different. Morning glories open early in the morning, and close about noon. Moonvines bloom at night.

Formerly called Calonyction, moonvines are now lumped by botanists with the other morning-glories as Ipomoea. The most popular and available one is Ipomoea alba (still often listed in catalogs as Calonyction aculeatum, or Ipomoea bona-nox). You will find seeds offered in such catalogs as Burpee, Park, Harris, Thompson & Morgan, and Hudson, and on some seed racks.

Moonvines are perennial plants in their native tropics. In other areas, grow them as annual vines. They are easy to grow. Start the vines indoors three weeks before the date of the last spring frost in your area. The hard, white seeds germinate faster if they're soaked overnight in warm water. Sow two softened seeds one inch deep in individual 4-inch plastic pots filled with sterile soilless mix. Cut out the weaker plant when the seedlings have their first true leaves. Keep them warm, and give them as much light as possible. I grow my moonvine seedlings under 16 hours of grow lights per day.

Moonvines grow fast, and begin to "run" as soon as they have their second set of leaves. Keep them vigorous with a weekly feeding of balanced 20-20-20 fertilizer with micronutrients, using 1/2 teaspoon per gallon of water. When frost danger is past, harden the seedlings by exposing them to increasing amounts of sunlight. Set them in the garden when they can tolerate a half day of full sun without wilting. Moonvines prefer not to be transplanted, but by starting them in pots and taking care not to disturb their roots when you plant them in the garden, they'll do just fine.

Plant moonvine seeds outdoors only after weather is warm and settled. It does no good to sow them when soil is cold and wet. Seeds usually rot, and the young plants turn yellow and stunt from cold.

Give the vines a place in full sun to get the fullest flowering. Provide a soil rich in organic matter and ample moisture. A three-inch mulch of compost or well-rotted manure will stabilize soil moisture, provide trace elements, and keep weeds down around the vines. Feed the vines once a month with a rose fertilizer. This promotes profuse flowering. Use twice the amount of fertilizer recommended for roses. You're feeding a big, vigorous vine. Pest control should not be needed, as seldom does any insect bother them.

Provide a sturdy support for moonvines to climb on when you plant them. Healthy vines will climb ten to 15 feet, but you can cut them back to any height you wish. Pinching out the growing tips of the runners also helps control height of the vines.

Moonvines are perfect for a porch, patio or any place they can be enjoyed in the evening. The vine makes a good screen throughout summer. The fragrant white flowers gleam in the dusk, and under a full moon.