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Anthesis
Ipomoea species are commonly named “Morning Glory” because the flowers of several cultivated species, notably I. indica, open at dawn and close before midday. However, while this observation may be a useful generalization, it is only a partial truth. Much depends on the strength of the sun and many morning-flowering species will continue in flower well into the afternoon on a dull day. Conversely night-flowering species, such as I. alba, I. muricata and I. violacea may remain open during clouded, sunless days. These observations indicate that research suggesting different species flower for a specific number of hours (Chemás-Jaramillo and Bullock 2005) should be treated with caution. However, there is no doubt about the truth of their observation that the flowers of some species, especially robust perennials, such as I. ampullacea, I. bracteata and I. pedicellaris, remain open for much longer periods than those of more slender species.
Economic uses
Much the most important species of Ipomoea economically is I. batatas, the sweet potato, which is reported to be amongst the ten most important staple food crops worldwide (Woolf 1992, FAO 2017). Although clearly of American origin it is widely cultivated in almost all tropical and subtropical countries for its root tubers (storage roots). The largest contemporary producer is China but much of Chinese production is used as animal fodder (FAO 2017). It has a number of important advantages as a human food. It is second only to the potato in productivity per hectare. It is more drought resistant than many important staple crops such as maize. The common orange-fleshed varieties are an outstanding source of Vitamin A and have significant quantities of Beta-carotene, potassium and various other elements important for human nutrition (Kurabachew 2015). Indeed per gram it is richer in potassium than bananas (USDA 2017. The purple-fleshed varieties have enjoyed a recent vogue as brain food but it is unclear whether this is merely a fashion fad or based on sound evidence.
Other species of Ipomoea produce root tubers but there are only occasional reports of their use, usually as a famine food. Amongst species whose tubers are reported to be used for food are I. leptophylla, I. pubescens, I. pandurata (Haddock et al. 2015), I. plummerae (Gutiérrez-R 2016) and I. serrana (Vasconcelas et al. 2016).
The leaves of some species of Ipomoea are used as a vegetable. Much the most important is I. aquatica, the water spinach or kangkong, which is widely used as a stir-fry vegetable in South East Asia, although it has not achieved much popularity outside the region. The leaves of other species are occasionally used as vegetables, including I. batatas itself and apparently I. littoralis (Austin 1991b), although it is unclear whether they enjoy general use or are a resort at times of famine. It is possible that the leaves of other species could be used as a vegetable but the leaves of some species are potentially harmful (Meira et al. 2012). Ipomoea malvaeoides and I. carnea subsp. fistulosa, for example, are avoided even by goats and are unpalatable, if not actually poisonous, to animals and presumably to humans.
Various species of Ipomoea are cultivated as garden ornamentals. In extra-tropical countries, relatively quick growing annual species are favoured, particularly I. indica, I. purpurea, I. nil, I. quamoclit and I. tricolor. In tropical countries, perennials are more common. The most conspicuous is I. carnea subsp. fistulosa, which is widely cultivated for its erect habit and profuse flowers. Ipomoea cairica is often planted to cover walls and unattractive bushes. Ipomoea alba and I. muricata are also sometimes grown in gardens and on boundary fences. Ipomoea horsfalliae is a widely planted liana that is grown in many tropical countries for its attractive red flowers, but is not reported to set seed and so is never naturalized. Ipomoea quamoclit and, less commonly, I. lobata are also grown quite frequently and sometimes become naturalised. There are occasional reports of the cultivation of other species including I. nervosa, I. pauciflora and I. intrapilosa but this is not common practice.
Various species of Ipomoea have had medicinal uses since pre-Colombian times, broadly for two purposes. The seeds of several species are known for their hallucinogenic properties as they contain small quantities of LSD-like substances (Steiner and Leistner 2018). Amongst the species used as a hallucinogen are I. tricolor “Heavenly Blue”, I. purpurea, I. alba, I. corymbosa and I. nervosa. The roots of several species have been used as a purgative and marketed under the name “jalapa”. Ipomoea purga is the best-known species used for this purpose but others such as I. simulans, I. orizabensis and I. jalapa are sometimes reported as having similar properties, although their medical value requires confirmation. Meira et al. (2012) document many actual and potential medical uses of Ipomoea species.
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