How to Grow Moonflowers and Care for Them

Moonflowers, with their ethereal beauty and nocturnal bloom, have enchanted gardeners throughout the ages. These tender, perennial vines, scientifically known as Ipomoea alba, add a touch of mystique to gardens while imparting an air of romance with their sweet fragrance and luminous blossoms. Learning how to grow moonflowers will reward your garden each year.

“The unique feature of the moonflower is that its five-to-eight-inch flowers bloom beginning at dusk and survive for that night only. The effect of seeing these large white blossoms in the nighttime light is magical,” says Bruce Bennett, certified professional horticulturist with Gardens by Design in Seattle, Washington.

Cultivating moonflowers in your own garden can be a gratifying experience, requiring patience, care, and a bit of know-how. In this guide, we'll explore everything to know about how to grow moonflowers from selecting the right location to nurturing them to full bloom.

Native to tropical and subtropical regions of North and South America, moonflowers are vines belonging to the family Convolvulaceae, which includes the pernicious weed known as morning glory. Unlike their diurnal counterparts, moonflowers bloom only at night, releasing a delicate perfume as they do so.

“The sweet scent is a combination of honeysuckle and vanilla and will attract nighttime pollinators, such as moths, bats, beetles, and even hummingbirds,” says Bennett.

These fast-growing vines can reach impressive heights, often climbing over trellises, fences, or arbors with ease. “Their vines twine around and can grow to 15 feet,” says Bennett. With their heart-shaped leaves and large, trumpet-like flowers, moonflowers are a dazzling sight, especially on warm summer nights when their blooms unfurl in the moonlight.

Location

“These vines thrive outdoors as perennial plants in USDA hardiness zones 10 to 12,” says Bennett. “Any cooler than that, treat them as annuals or as potted plants that are brought indoors for the winter.” Moonflowers enjoy full sun and won’t mind the harsher afternoon sunshine, so select a spot in your garden that receives at least six to eight hours of direct sunlight each day.

A word of caution: Moonflowers are toxic if ingested, so be sure to plant them away from areas where pets and kids play.

Soil

An essential part of knowing how to grow moonflowers is ensuring that the soil drains well.

“Moonflowers prefer neutral, loamy soil, but the plants will do well as long as the drainage is good,” says Bennett. He recommends prepping your garden by adding one part perlite or vermiculite (to improve drainage) to two parts compost, amending a four-foot circle of soil where the vine will be planted.

Timing

You can grow moonflowers from either seeds or seedlings, but many gardeners prefer to start from seed for a more economical and rewarding experience. To plant moonflower seeds, wait till the final spring frost has passed and the soil has warmed.

“As most of the country has less heat than these plants like, they will benefit from starting the seeds indoors six weeks before transplanting them outdoors in mid-May,” Bennett says. “Large leaves appear as the plant climbs over its trellis support structure. Finally, in late August, I begin to see buds. By mid-September, the blooms begin to unfurl as evening approaches. The bud opens quickly, which is a thrill to watch! By dawn the next day, the flower fades.”

Germinating Seeds

Once the seeds germinate and get growing, moonflowers are pretty carefree, says Bennett. They’ll seem to grow slowly at first and then take off.

Tips on how to start moonflower seeds:

• Soak the seeds in water overnight to soften the hard outer covering.
• Use nail clippers to snip off an edge of the seed covering and make it easier for the new plant to grow out of its confines.
• Whether you're sowing seeds or transplanting starts, wait until the soil temperature nears 70 degrees. The seeds won’t germinate in cold soil.
• Plant the starts about ¼ inch deep in individual cells or small pots. Keep moist and warm.
• Keep the vines looking neat by giving them something to climb. Otherwise, they may sprawl and collapse under their own weight.
• Deadheading moonflowers will encourage more blooms, but you don't have to snip every single one. They’ll keep flowering even if you miss a few.

Once the moonflower seeds have germinated, it's essential to provide proper care to help your plants flourish.

Water

“As these vines are actively growing in the warmer part of the year, consider giving them five gallons of water once a week,” Bennett says. “One of the easiest ways to do this is to drill a few holes on the bottom-outside edge of a five-gallon container, fill the container full of water, and walk away until the next week,” he says.

Fertilizer

If you amended the soil with compost before planting, that’s all you’ll need to do. If not, Bennett recommends adding a slow-release organic fertilizer around the plant in May.

Support Structures

Moonflowers are vigorous climbers, quickly scaling any nearby structure in their quest for sunlight. Young seedlings benefit from having something to climb, such as a trellis or wire mesh. As the seedlings grow, thin them out to allow adequate space for each plant to flourish. Regularly check the supports for stability and make any necessary adjustments to ensure the safety of your moonflower vines.

“Remember, the vines can grow upwards of 15 feet tall and six feet wide,” says Bennett.

Pruning

For improved flowering, Bennett recommends removing as many spent flowers as possible. “Pruning is pretty much limited to aesthetics, to keep the vines contained, or to redirect the growth energy,” he says.

Pest management

While moonflowers are relatively pest- and disease-resistant, they may occasionally encounter common garden pests such as aphids, spider mites, or whiteflies.

“A strong blast of water from a hose can dislodge most of these pests, but, for more stubborn infestations, neem oil or insecticidal soap can be used,” says Bennett.

Additionally, practice good garden hygiene by removing any fallen debris or diseased plant material to prevent the spread of any fungus.

Assuming the plant starts are put out in May, flowers should begin to appear in late August and bloom through October, Bennett says.

The flowers typically begin to open in the late afternoon and reach their peak fragrance and beauty after nightfall. Take the time to admire their delicate petals, which may range in color from pure white to pale pink, and inhale their lovely scent. Consider cutting a few blossoms to enjoy indoors or share with friends, but leave plenty on the vine to attract pollinators and ensure a bountiful display throughout the growing season.

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Expert consulted:Bruce Bennett

Garden Designer

Bruce Bennett is a Seattle-based garden designer and consultant with nearly 30 years of experience in the Pacific Northwest. Trained as a Master Gardener and holding multiple horticultural certifications, he has also served as Director of Education for the Master Gardener Program Foundation of King County. Now retired from his landscape design company, Bruce teaches in WSU Extension’s "Growing Groceries" program and contributes gardening articles to various publications. Additionally, he volunteers as an interpretive ranger, creating classes and lectures for national and state parks and integrating these experiences into his gardening columns.