Commercial vanilla is always propagated by stem cuttings. In vegetative propagation, the cuttings should be taken from healthy vigorous plants and may be cut from any part of the vine. The length of the cutting is usually determined by the amount of planting material available. Short cuttings, 20 cm in length, will take 3 to 4 years to flower and fruit. Cuttings, 90-100 cm in length, are usually preferable. In some regions, cuttings 2-3.5 mm in length may be used. When available, with their free ends hanging over supports; these will flower and fruit in 1 to 2 years. It is usual to remove two to three leaves from the base, which is inserted into the humiclayer and mulch. With short cuttings, at least two nodes should be left above ground. The portions above ground should be tied to the support until the aerial roots have obtained a firm grasp. Cuttings are usually planted in situ, but they can be started in nursery beds when necessary. Because of their succulent nature, cuttings can be stored or transported for periods of up to two weeks if required.
The vines of vanilla require some form of support up which to climb, and also light shade; too dense shade and full sunlight are both deleterious. The ideal tree should be quick-growing, providing light, checkered shade; have sufficient low branches providing easy access to the vanilla; be strong enough to support the vines in strong winds; and be easily pruned when necessary. It is an advantage if it can be planted from large cuttings and it may be possible that it can provide an economic product as well as the vanilla. The two trees most commonly used in the Malagasy Republic are the physic nut, Jatrpopha curcas L, which can be propagated from cuttings or grows rapidly from seeds, and Casuarina equiserifolia L. In the early stage, lateral shade may be provided by bananas or maize. Windbreaks should be planted where necessary. If vanilla is grown up posts or trellises, it will also be necessary to supply some form of partial shade. The woodwork is subject to decay and damage by termites, necessitating its replacement at regular intervals. In Madagascar, supports are generally planted from September to November after cleaning the land.
PLANTING AND AFTER-CARE
The cuttings are usually planted about 3 meters apart at the foot of the supporting trees or poles. A spacing of 1.2 - 1.5 meters in rows 2.5 - 3 meters apart is also sometimes recommended. In the early vanilleries, the plants were often planted so close together that they became entangled. This usually gave very high initial yields, but presented grave problems of access and disease control later. It is necessary to train the vines so that they may grow at a convenient height for pollination and harvesting. The vines are twisted round the lower branches of the supporting tree or over the lattice of the trellis so that they may hang down. Care is required so as not to tear or bruise the leaves, branches or roots. The top 7.5 - 10 cm of the vine is usually pinched out 6 - 8 months before the flowering season to encourage the reproduction of inflorescences in the axils of the leaves on the hanging branches. Vanilla usually starts flowering in its third year after planting, the time taken depending on the size of the original cuttings. The maximum production of flowers is reached in 7 to 8 years. Given proper care this may continue for years, but in some vanilleries the production period is shorter. As the flower opens, the requisite number are hand-pollinated. Only the flowers on the lower side of the raceme are pollinated in order that the fruits may hang perpendicularly to produce straight beans; those on the upper side would produce crooked beans of inferior quality. Usually only one flower opens in each inflorescence in one day and is receptive for about 8 hours. Consequently, most of the pollination must be done in the mornings and is continued for 1 or 2 months until the required number of fruits have set. The number of inflorescences and flower per vine, and the number which are pollinated and allowed to produce mature beans, 8 - 10 flowers on 10 - 20 inflorescences are pollinated, of which 4 - 8 capsules are allowed to grow to maturity on each size. If pollination has been a failure, the flowers drop off the next day. When the desired number of fruits has set, the remaining buds are removed, which may be done by clipping off the tip of the inflorescence. Damaged and malformed capsules are removed during growth. The final number of beans per vine varies greatly and is usually about 30 - 150.
HARVESTING AND YIELDS
The time between flowering and harvesting is 6 - 9 months. The pods are harvested rotationally when they are fully grown and as they begin to ripen, as shown by the tips becoming yellow. It is essential to pick to pods at the right stage as immature pods produce and inferior product and if picked too late they will split during curing. The plantations should be visited daily so that the pods can be picked as soon as they are ready. They may be harvested by sideways pressure of the thumb at the base or by cutting with a sharp knife. About 6 kg of green pods produce 1 kg of cured beans. Curing should begin within a week of harvesting the beans. This process is discussed in detail in the "Processing and Manufacture" section. After fruiting, the old stems and weak branches are pruned off. The tree supports or shade should be pruned to provide 30 - 50 percent of full sunlight and to induce branches at the correct height for training the vines. In some countries it is customary for the owners to prick distinguishing marks on the green pods on the vines to ensure against theft. Yields are very variable. A good vanillery is said to yield about 500 - 800 kilograms of cured beans per hectare per annum during a crop life is about 7 years.