Morning glories (Ipomoea spp.) and moonflowers (Ipomoea alba) are closely related tropical flowering vines that share common characteristics, such as broad, heart-shaped leaves; showy, trumpet-shaped flowers; and a vigorous, twining growth habit. Care requirements are nearly identical for the two plants, which are notably low-maintenance and easy to care for.
Numerous species and cultivars of morning glories are available in the nursery trade, showcasing flowers in a range of colors. The common morning glory (Ipomoea tricolor) cultivar "Heavenly Blue," with its light blue-and-white flowers, is perhaps the most iconic morning glory, according to Floridata. However, moonflowers are available only in pure white. Both morning glories and moonflowers produce flowers that may be up to 6 inches in diameter. Morning glories open in the morning, lasting for one day and producing no noticeable scent, while moonflowers open in the evening with a delicate fragrance.
Both plants hail from the American tropics and can be grown as perennials only in frost-free conditions. Morning glories may be grown as perennials in U.S. Department of Agriculture plant hardiness zones 10 and 11, while moonflowers do well in USDA zones 10 through 12. Both are fast-growing enough to be utilized as annuals in cooler climates. A location with full sunlight allows both plants to flower prolifically. Moonflowers have more sensitive leaves, which benefit from protection from strong winds lest they become ragged.
Both plants are tolerant of a range of cultural conditions as long as the soil drains well. Water regularly so that soil becomes moist but not waterlogged or flooded. Adding mushroom compost or other types of organic compost to the soil helps to increase plant vigor. Regular nitrogen fertilizer can lead to an excess of leaves at the expense of flowers. Both plants have a climbing habit and look their best if allowed to travel up a trellis, arbor or other structure.
Morning glories and moonflowers may both be propagated by seeds, started indoors about six to eight weeks before the last frosts of spring. Both vines have tough seeds that germinate better if nicked with a knife or soaked overnight in warm water. You can start seeds directly in the garden in late spring, though this considerably shortens their bloom period. Seeds can be harvested off the vine in fall for use during the following spring.