Flat-leaved vanilla
There are about 100 different species of Vanilla, but it is Vanilla planifolia that produces 95% of the world's commercially-produced vanilla. This species originates from Mexico and Central America, where it grows as a vine, climbing through trees in humid, warm (21-32 degrees Celsius) lowland forests. The vines, which can reach up to 30 metres in length, are made up of thick, fleshy stems with alternating leaves and a root arising at each node. Short, dry periods encourage the production of the large, pale yellow-green flowers. The flowers have a trumpet-like lip, slight fragrance and open in the morning; lasting for no more than eight hours.
Vanilla is naturally pollinated by bees native to Mexico and Central America. Consequently, when it was introduced to other parts of the world, pollination and hence fruit production became a major problem. A method for artificial pollination was discovered in 1836, and improved upon in Réunion in 1841. Now, all commercially-produced vanilla is pollinated by hand, including in Mexico. This needs to be done in the morning while the flowers are still receptive. Once pollinated, the ovaries swell and develop into fruits called 'pods', which look like thin runner beans. Most vanilla production takes place in Madagascar, Réunion, the Comoro Islands and, to a lesser extent, Indonesia and Mexico.
One skilled worker can pollinate 1,000 to 2,000 flowers per day. This labour-intensive process makes vanilla the world's second-most expensive spice after saffron (Crocus sativus). When the desired number of fruits on a plant has been set, the other buds are removed and after about eight months the pods are harvested and cured by a means of sweating and drying. This process produces a complex mixture of chemicals, including the aldehyde vanillin.
Vanilla was 'discovered' by sixteenth-century Spanish conquistadors in Mexico when they found the Aztec people using it to flavour chocolate. It was also used to treat ailments such as hysteria, melancholy and impotence. Today it is used as a food flavouring and in the perfumery industry.
If produced commercially, vines tend to be grown in pots and up poles that enable the plants to climb, as they will only flower when they have gained considerable length. When grown in a glasshouse, they are often grown in baskets so that the stems can be turned back on themselves. Good light is needed to encourage flowering; therefore, the closer to the glasshouse roof, the better.
Further reading
Bory, S et al. 2008. Patterns of introduction and diversification of Vanilla planifolia (Orchidaceae) in Reunion Island (Indian Ocean). American Journal of Botany 95: 805-815.
Lubinsky P et al. 2008. Origins and dispersal of cultivated vanilla (Vanilla planifolia Jacks. [Orchidaceae]). Economic Botany 62: 127.
Purseglove JW 1972. Tropical Crops, Monocotyledons. Longman Scientific & Technical.
Lucinda Lachelin