Moonflowers (Ipomoea alba) produce ghostly white flowers that open in late afternoon and early evening. These tall-growing vines are perennials in U.S. Department of Agriculture plant hardiness zones 9 through 11 and thrive as annuals in any climate. Moonflowers, also called moonflower vines, moon vines and evening glory, form seedpods after their flowers decline. The way to handle these pods in fall depends on whether you want more moonflowers or want to prevent the plants from spreading.
Each moonflower seedpod contains a single large, black seed. If you wish to harvest the seeds to plant them in the future, then pick the pods from the moonflowers in fall as soon as the pods dry and begin to split open. You may loose some seeds if the pods split completely before you get to them. Moonflowers produce many pods, however, and so plenty should be left to harvest. Insert your thumbnail into each pod's split to open the pod all the way, and shake the seed out of each pod and into a bowl.
Although moonflower seeds dry almost completely while their pods are on the plants, you can ensure better storage life for the seeds by drying them a bit longer after collecting them. Spread the seeds on a tray, and place the tray in a dark, warm and dry location for three to five days; excess moisture will evaporate from the seeds during that time. When dry, the seeds can be packaged in an airtight, labeled container. Store the seeds' container in a cool location until planting time in spring. Moonflower seeds germinate best in spring when soaked in warm water overnight just before they are sown.
Moonflowers may self-sow in your garden, eliminating the need to replant them each year, which is especially helpful if you have a thin planting or moonflowers grow only as annuals in your area. If you want your moonflowers to self-sow, then allow their seedpods to ripen fully and dry on the plants in fall. Cut the vines to the ground only after the seeds have dropped from the pods. Keeping the garden bed's soil moist, but not soggy, throughout winter helps weaken the seed coats so the seeds are more likely to germinate in spring.
Self-seeding can pose a problem because the moonflower planting may become too dense or spread to other garden beds. In order to minimize that problem, remove all the moonflower seedpods in fall before they have a chance to dry and drop seeds. Because moonflowers produce new blooms daily throughout summer, removing their seedpods in only fall isn't sufficient to stop all self-seeding. Deadhead the plants every two or three days throughout their flowering period by pinching off the spent blooms before they have a chance to form viable seedpods.
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