TEXT & IMAGES EVELYN ROE
Colourful trumpets silently herald a new day: morning glory flowers unfurl at dawn, the tubes of fused petals remaining a little creased from their night of twisting in tight buds. These twining herbs and shrubs are found throughout the tropics, and in Zambia there are many species, some native and some visitors, flowering across the seasons. Thus, we can almost always find an example of the Convolvulaceae in bloom, even in winter.
Among the native species, Ipomoea shirambensis (locally known as lukuli) brings an astonishing burst of colour to the otherwise parched landscape at the end of the dry season, while I.rubens decorates riverside and swampy vegetation for months on end.
Ipomoea pestigridis and Convolvulus sagittatus, named after the tiger-foot and arrow-like shape of their leaves respectively, are also indigenous to this region of Africa. A non-native, but much-planted Ipomoea is the sweet potato, I. batatas, which probably originated in South America. Its leaves and tubers are highly nutritious and are among the most prominent of vegetables in Zambia, known locally askandolo, chimbwaliand ngulu.
Not only do the tubers taste sweet, they also help to balance blood sugar levels by reducing insulin resistance and thus alleviating symptoms of type-2 diabetes. Ipomoeaaquatica, found floating at the edges of the Zambezi, and other rivers and swamps, is biochemically very similar to the sweet potato, and both species contain compounds known to inhibit HIV replication [reference* given below].
Ipomoea tricolor, a garden escapee originally from tropical America, may turn out to be one of nature’s gifts to help us fight the dreaded Staphylococcus aureus bacteria, which have become resistant to a wide range of antibiotics: extracts from leaves and roots contain a range of compounds which act synergistically to disable the mechanism of resistance, thus allowing the active substances in prescribed antibiotics to take effect. Other than the species which are known to be edible, do not consume morning glory plants. Many of the seeds are poisonous, with effects ranging from mildly laxative (interestingly, since the other common name for the family is ‘bindweed’!) to psychosis. Ipomoea tricolor seeds, for example, were used by the Aztecs in shamanistic rituals to give their victims mind-altering horror trips.
However, literally hundreds of species of Ipomoea worldwide are known to have effective and wide-ranging medicinal properties, so perhaps we should promote research into our local species. After all, they can’t blow their own trumpets.
*[ref: Meira, M. et al. (2012). Review of the genus Ipomoea: traditional uses, chemistry, and biological activities. Brazilian Journal of Pharmacognosy, 22(3): 682-7134]
More articles in this series:
Christmas crackers (ZT, Issue 15, Dec 2013)
Don't eat the daffodils (ZT, Issue 14, Sept 2013)
Rainforest Riches (ZT, Issue 13, June 2013)
Berry banquet (ZT, Issue 12, March 2013)
Marvellous Mangoes (ZT, Issue 11, December 2012)
Underground Forests (ZT, Issue 10, September 2012)
The healing powers of Aloes (ZT, Issue 09, June 2012)
Dogbane Drugs (ZT, Issue 08, March 2012)
Devil’s Claw (ZT, Issue 07, December 2011)
Elephant Toothpicks (ZT, Issue 06, Sept 2011)