Introduction:
Japanese engraving of Ipomoea nil cultivars.
In Europe the common bindweed (Convolvulus arvensis) is a well known member of the Convolvulaceae family. Some gardeners will also be familiar with a few American annual climbers: Ipomoea tricolor, I. purpurea and I. nil; more often called Morning Glories. Also well known is Convolvulus tricolor or the Dwarf Morning Glory; a prostrate herbaceous species from the Mediterranean basin.
At the beginning of the last century the number of cultivated species was more important and the bindweed was even used in some gardens. The invasive nature of C. arvensis, as well as the climbing habit of most species, seem to have discouraged many gardeners. As opposed to more architectural plants the Convolvulaceae are well appreciated in more ‘natural’ looking gardens. Nevertheless, since the 1600s, a few species imported from America arrived in Asia. In Japan, it became an obsession and hundreds of cultivars were bred. Ipomoea nil in Japan represents the imperial flower and it is often called I. imperialis.
One well known feature of this family is the climbing habit and the twining stems (also called volūbile in latin and other languages). The name Convolvulaceae does in fact reveal this feature in its name: convolvere is a Latin verb meaning rolling or winding. But despite the fact that many species are twining, the large funnel-shaped and colourful flowers that never open more than one day, are characteristic for the family.
In European and Japanese cultures the bindweeds are associated with humility; but Mexican, North American, Australian and African cultures seem to worship this family the most. Aztec people used the seeds of I. tricolor and Turbina corymbosa for their hallucinogenic properties and to help their communion with their gods. Those hallucinogenic properties were only rediscovered in 1940, some time after cultivars like Ipomoea tricolor ‘Heavenily Blue’ and ‘Pearly Gates’ were named. In North America the wild potato vine (Ipomoea pandurata) is a sacred plant of the Iroquois; this species can heal or harm and must be harvested with great care; associated with sunflowers seeds they are used in seasonal ceremonies.
The indigenous Australians use the large deep underground tubers of Ipomoea costata as a food source, it is also mentioned in their mythology. In Gabon Ipomoea cairica gives luck to fisherman and Ipomoea involucrata helps fecundity.
The Convolvulaceae are present in most cultures and because they are widespread they are often used for food, medicine and horticulture. The new world has provided us with the sweet potato (Ipomoea batatas) actually the seventh most used foodstuff. Some 9000 years old fossilized tubers were found in the Andes and the first cultivation could be dated as early as 2400 BC. Though the introduction of the sweet potato is often attributed to Christopher Colombus it had been cultivated in New Guinea as well as New Zealand a long time before.
Leaves of Ipomoea aquatica are a commonly used vegetable in tropical Asia and they can be stored for a long time in a bucket of water. Floral peduncles of Ipomoea alba are sometimes also eaten but this is not very common. Many uses of the different species may not be known yet, like tuberous species in desert areas that store water in their tubers.
In medicine, many species are used locally, like in Indonesia because of its purgative faculties. Ipomoea jalapa of central America produces a resin used as a purgative. In Egypt, sculpted frescos representing Convolvulus scammonia indicate a possible use of this species as purgative as well as to abort pregnancy (uses also known in Gabon with the leaves of Ipomoea batatas). In Asia it is the roots of Operculina turpethum that are used for the same effect. Finally a more unexpected use can be recorded on the Canary Islands where wood of Convolvulus floridus and C. scoparius is used to produce a scented powder.
Nowadays it seems that the horticultural use as well as medicinal qualities are the most researched, and many species could be introduced into cultivation, though most species only thrive in warm climates.