Vanilla, being a climbing orchid, requires standards for support and shade. A number of tree species have been recommended as suitable standards for vanilla. Apart from live standards, trellis, latticework, wooden and concrete posts, and wire or bars are used as support for vanilla vines. Wooden posts are subject to decay and to the attack of termites and hence it becomes necessary to replace them at frequent intervals. In case of wire or bar supports, the tender portion of the vines may be easily broken. When nonliving supports are used, it is always necessary to provide some form of partial shade for the vanilla plants. Hence, live standards are preferred for vanilla cultivation.
In general, the support tree species with small leaves, which permit filtered light through the foliage, are useful. Species that can easily be propagated through long stem cuttings and those that grow faster and produce branches sufficiently low (from 1.5 to 2.0 m from the ground) for the vines to hang within easy reach of the workers are found to be the most ideal. The trees should be strong enough to support the heavy growth of vines and beans and should withstand strong wind and rainfall. Trees should never entirely defoliate during summer months, but should be amenable for periodic pruning for shade regulation. It is also important for the support trees to have deep penetrating roots so that they do not compete with the shallow rooted vanilla plants for nutrients. Some of the common suitable support trees used in India are Gliricidia maculate, P. alba, Morus sp. Casuarina, Liberian coffee, Coral tree, Lebeek tree, E. lithosperma, Jatropha sp., and so forth.
Planting
Vines of 1 m length either from plantation/trench nurseries/polybag rooted cuttings are generally preferred for planting. Cuttings are planted close to the base of the support tree by laying the 3–4 basal nodes, from where leaves have been removed, on to the soil surface and gently pressing these nodes to the soil or putting sufficient soil to cover the nodes. While planting, care should be taken to ensure that the basal cut end portion of the cutting is kept just above the soil surface, as otherwise chances of decay are more. The top end of the cutting is to be tied to the base of the support tree gently so that it will eventually climb on to them. Partially decomposed organic materials such as coconut husk, mulch, straw leaves, and so on should be placed over the newly planted cutting at the base of the support tree to a thickness of 10–15 cm or more. If shade is not sufficient from the support tree, palm fronds or other leaves can be used to provide shade to cuttings.
The ideal time for planting vanilla is when the weather is neither too rainy nor too dry. Planting in August or September after the southwest monsoon is recommended under Indian conditions. It takes about 4–8 weeks for the cuttings to strike roots and to show initial signs of growth from any one of the leaf axils. Under irrigated conditions, rooted polybag cuttings could be planted any time of the year.
After Care
A vanilla plantation has to be given constant attention after its establishment. It should be frequently visited to train the vines to grow at a convenient height, prune the growing vines and tree supports, and observe diseased and pest-infected plants. Cultivation of other crops near the roots is not advisable as it may disturb the roots and soil leading to damage of vanilla plants. Periodical removal of dead vines or rotting portion of vines is to be undertaken regularly. Success of the plantation would depend on preventing any serious outbreak of diseases and creating favorable conditions for flowering and beans production.
Nutrient Management
Vanilla, being a hemiterrestrial orchid, providing right soil environment at the plant base through appropriate mulching, rather than soil fertility per se, is important for its successful cultivation. The best source of nutrients is the deep layer of decomposed mulch maintained over and around the vanilla roots. The nutrient-supplying capacity of mulch depends on the source and composition of the mulch.
Nutritional studies carried out at the ICRI, Spices Board has indicated that vanilla yield can be enhanced by soil application of 20:10:30 g NPK per vine per year and foliar application of urea, single super phosphate, and muriate of potash at the rate of 1.0%, 0.5%, and 1.5%, respectively, during January, May, and September. The crop responds well to foliar application, and therefore during the initial years of vanilla growth, foliar application of inorganic manures is practiced. DAP (2%) and muriate of potash (1%) or NPK complex (2%) may be sprayed on the lower surface of the leaves when adequate humidity (>60%) is available in the plantation. Foliar application of DAP and micronutrients, particularly Zn and B boost the development of pods. Studies on the effect of nutrient uptake through aerial roots of vanilla revealed that Knop’s solution (25%) showed improvement in the growth of vanilla (ICRI, 2003).
The crop is highly amenable to organic cultivation. In addition to chemical fertilizers, various organic manures are applied to vanilla. Decomposed organic matter, bone meal, FYM, vermicompost, and fermented deoiled cakes are applied at least twice in a year, that is, during June–July and September–October. Foliar application of vermin wash (1:5 dilutions) favored the growth and development. Application of Vyrsha ayurvedic preparations such as panchakavya, fish amino extract, and egg amino extract is also being widely practiced under organic vanilla cultivation.
Mulching
Mulching with green or dry leaves is to be carried out at least twice in a year. They not only provide food in the form of potassium-rich organic matter but also conserve moisture and hold the layer of mulch in position, creating a deep and rich root zone that vanilla favors. In studies on the growth performance of vanilla with various mulch materials, coir pith favored relatively better vine elongation compared to traditionally used wood debris mulch. The advantage of coir pith is attributed to better moisture conservation, maintenance of conducive microclimate, and supply of micro- and macronutrients for vanilla growth (ICRI, 2005).
Irrigation
Vanilla requires a moist climate with frequent but not excessive rains. Under excessive rainfall, there is widespread occurrence of rot diseases. Under prolonged drought conditions, the plants may suffer from physiological damage and the vines may not recover. In extremely dry conditions, irrigation should be provided at least once in 4–5 days. Mulching with mango leaves (25 kg per vine per year) and watering once in four days was found to increase vanilla yield (Muraleedharan, 1975). Depending on the area under cultivation, sprinkler or hose irrigation may be practiced. Microsprinkler/fog irrigation is advocated to maintain relatively high humidity levels in the plantations to ensure high percentage of bean sets. Care should be taken to avoid water stagnation around the plant base or excessive water stress at any point of vine or pod development.
Shade Management
Careful lopping of branches of the support tree is very important to give shade to vanilla plants. Newport (1910) stated that checkered shade rather than dense shade is to be preferred. Vanilla vines require more sunlight than shade during flowering and at the time when the beans are maturing.
It is the farmers experience that the existing shade trees should be pruned to admit sunlight as uniformly as possible, 30–50%. It may be desirable to regulate shade allowing more light during the blossoming period. Allowing more light is helpful to check vegetative growth and favor flowering. Heavy shade should be avoided because the stem will become thin, leaves small, and flowering and fruiting generally reduced. Under too much sunlight, on the contrary, the leaves not only get sunscald and turn yellow but the plants become weak during a drought period and more susceptible to root rot diseases. The amount of light vanilla can tolerate depends mainly on the water supply to the roots as influenced by the atmospheric humidity and irrigation practices.