Daytime isn't the only time to enjoy your garden, especially when some of the most sweetly fragrant flowers bloom at night. Moonflowers (Ipomoea alba) produce pale white flowers that only bloom in the evening and at night, resembling the full moon that's their namesake. These tall vines grow as perennials in U.S. Department of Agriculture plant hardiness zones to 10 through 12, but they are usually treated as annuals. Moonflowers grow with only minimal care and maintenance from spring through early fall.
Moonflowers may flower at night, but they require a full six or more hours of daily sun to produce healthy growth. The vines tolerate most soil conditions, so you can grow then in any well-drained garden bed. Soil that remains moist without becoming soggy results in the healthiest moonflowers. You can achieve this by working a 2-inch layer of compost into the site before you plant. Although moonflowers need moist soil, they can't tolerate soggy conditions, so avoid low-lying areas where water tends to pool or those that become muddy after rain.
Moonflower vines can grow up to 15 feet tall, so they need a support to keep them upright. A tall fence or trellis usually provides this support. The moodflowers don't require trying or training to the support because they can climb on their own. You can keep the plants trimmed to a height as low as 6 feet if you are growing them along a shorter support. Pinch out the top of each vine as it reaches the top of the fence to encourage branching and delay further upward growth.
Water and Fertilizer
Moist soil results in healthy growth and minimizes most plant problems. Supplying moonflowers with about 1 inch of water weekly from rain or supplemental watering, which is enough to moisten the top 6 inches of soil, is usually enough unless the soil is drying quickly because of high temperatures. A 2-inch layer of mulch over the top of the bed helps prevent moisture loss and keeps the soil moist. Moonflowers rarely require any fertilizer. Adding compost before you plant supplies enough nutrients to carry the plants through the summer.
Few pests or diseases bother moonflowers. Proper watering and a sunny site prevent most issues. Weeds may infest the bed, but using a mulch suppresses them as long as you pull stray weeds before they set seed. Moonflowers readily self-seed but they rarely become invasive. Planting in the same area each year prevents them from popping up unwanted in the bed. You can also pinch off the wilting blooms each day to prevent seeds from forming. All portions of moonflower plants are toxic. Do not allow children or pets to put any portion of the plant into their mouth.