The genus Ipomoea is the largest in the family Convolvulaceae, with over 500 species. Most of these are called "morning glories", but this can refer to related genera also. Those formerly separated in Calonyction are called "moonflowers". The genus occurs throughout the tropical and subtropical regions of the world, and comprises annual and perennial herbaceous plants, lianas, shrubs and small trees; most of the species are twining climbing plants.
Human use of Ipomoea is threefold: First, most species have spectacular, colorful flowers and are often grown as ornamental plants, and a number of cultivars have been developed. Their deep flowers attract large Lepidoptera - especially Sphingidae such as the Pink-spotted Hawkmoth (Agrius cingulata) -, or even hummingbirds.
Second, the genus includes food crops; the tubers of Sweet Potato (I. batatas) and the leaves of Water Spinach (I. aquatica) are commercially important food items and have been for millennia. The Sweet Potato is one of the Polynesian "canoe plants", transplanted by settlers on islands all over that ocean. Water Spinach is used all over eastern Asia and the warmer regions of the Americas as a key component of well-known dishes such as Canh chua rau muống (Mekong sour soup) or Callaloo; its numerous local names attest to its popularity. Other species are used on a smaller scale, e.g. the Whitestar Potato (I. lacunosa) traditionally eaten by some Native Americans like the Chiricahua Apaches, or the Australian Bush Potato (I. costata).
Moon Vine (I. alba) sap was used for vulcanization of the latex of Castilla elastica (Panama rubber tree, Nahuatl: olicuáhuitl) to rubber; as it happes, the rubber tree seems well-suited for the vine to twine up upon, and the two species are often found together. As early as 1600 BCE, the Olmecs started to produce the balls used in the important Mesoamerican ballgame thus.
The root called John the Conqueror in hoodoo and used in lucky and/or sexual charms (though apparently not as a component of love potions) usually seems to be from I. jalapa. The testicle-like dried tubers are carried as an amulet and rubbed by the user to gain good luck in gambling or flirting. As Willie Dixon wrote, somewhat tongue-in-cheek, in his song "Rub My Root" (a Muddy Waters version is titled "My John the Conquer Root"):
- My pistol may snap, my mojo is frail
- But I rub my root, my luck will never fail
- When I rub my root, my John the Conquer root
- Aww, you know there ain't nothin' she can do, Lord,
- I rub my John the Conquer root
The third way humans use Ipomoea is due to these plants' content of medically and psychoactive compounds, mainly alkaloids. Some species are renowned for their properties in folk medicine and herbalism; for example Vera Cruz Jalap (I. jalapa) and Tampico Jalap (I. simulans) are used to produce jalap, a cathartic preparation accelerating the passage of stool. Kiribadu Ala (Giant Potato, I. mauritiana) is one of the many ingredients of chyawanprash, the ancient Ayurvedic tonic called "the elixir of life" for its wide-ranging properties.
Other species were and still are as a potent entheogen. Seeds of Mexican Morning Glory (tlitliltzin, I. tricolor) were thus used by Aztecs and Zapotecs in shamanistic and priestly divination rituals, and at least by the former also as a poison, to give the victim a "horror trip"; see also Aztec entheogenic complex. Beach Moonflower (I. violacea) was also used thus, and the cultivars called Heavenly Blue Morning Glory, touted today for their psychoactive properties, seem to represent an indeterminable assembly or hybrids of these two species.
Responsible for the entheogenic activity are probably ergoline derivatives (lysergamides). Ergine (LSA), isoergine, D-lysergic acid N-(α-hydroxyethyl)amide and lysergol have been isolated from I. tricolor, I. violacea and/or Purple Morning Glory (I. purpurea), but although these are often assumed to be the cause of the plants' effects, this is not supported by scientific studies which show that although pyschoactive these compounds are not notably psychoactive or hallucinogenic. Alexander Shulgin in TiHKAL suggests that ergonovine is responsible instead, having verified psychoactive properties, though it is not unlikely that yet other undiscovered lysergamides are present in the seeds.
Though most often noted as a drug, the lysergamides are also of medical importance. Ergonovine enhances the action of oxytocin, used to still postpartum bleeding. Ergine induces drowsiness and a relaxed state and might be useful in treating anxiety disorder. Whether Ipomoea species are a useful source of these compounds remains to be determined. In any case, in some jurisdictions certain Ipomoea are regulated, e.g. by the Louisiana State Act 159 which bans cultivation of I. violacea except for ornamental purposes.
Many herbivores avoid morning glories like Ipomoea, as the high alkaloid content makes these plants unpalatable, if not toxic. Nonetheless, Ipomoea species are used as food plants by the caterpillars of certain Lepidoptera (butterflies and moths); see list of Lepidoptera which feed on Ipomoea. For a selection of diseases of the Sweet Potato (I. batatas), many of which also infect other members of this genus, see List of sweet potato diseases.