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Chapter 6. Cultivation Systems
Juan Hernández Hernández and Pesach Lubinsky
Introduction
Vanilla (Vanilla planifolia) is a rare perennial, hemi-epiphytic succulent herb that makes use of forest trees in its natural habitat for support, shade, and natural humus. The forests, where wild V. planifolia are found, are classified as selva alta perenni-folia (tall evergreen tropical forest), the wettest of the tropical forests. Today, V. plani-folia is cultivated in different production systems that mimic to some degree the agro-ecological parameters that are found in the natural habitat of the species. The cultivation techniques and management practices for vanilla have improved mostly from trial and error by vanilla producers worldwide. On the contrary, empirical agronomic studies of vanilla are largely lacking.
This chapter details the agro-ecological requirements, systems of production, propagation, cultivation/management, and flowering/pollination and harvest of V. planifolia. This information is based largely on observation, experiment, and on published articles and cultivation manuals authored by people with personal experience in vanilla cultivation.
Agro-Ecological Conditions
To reach optimal conditions for growth and production, vanilla cultivation requires the following agro-ecological parameters.
Climate
V. planifolia thrives in hot-humid tropical climates.
Temperature
V. planifolia grows best in temperatures ranging from 20°C to 30°C (Childers and Cibes, 1948; Ranadive, 2005), and may tolerate high temperature of 32°C (Purseglove et al., 1981; Anandaraj et al., 2005). Temperatures reaching below 20°C inhibit plant growth and flowering intensity (Ranadive, 2005); temperatures exceeding 32°C cause yellowing of vegetative parts and premature fruit drop (Anandaraj et al., 2005; Hernández Hernández, 2007b).
Precipitation
V. planifolia requires an annual average precipitation from 2000 to 3000 mm (Sasikumar et al., 1992; Soto Arenas, 2003), it is well distributed throughout the year except during flowering/pollination. Since heavy rains may diminish successful pollination and fruit set, it is best to irrigate the plants at their bases during flowering. V. planifolia needs 2–3 relatively dry months to stimulate flowering. In areas where average annual precipitation exceeds 3000 mm, plants are more prone to fungal attack (e.g., Fusarium sp.). At the other extreme, that is, where precipitation is less than 2000 mm, and where a system of irrigation is not in place, the lack of water greatly compromises the ability of the plant to perform basic physiological functions.
Altitude
The best altitudes for cultivating V. planifolia are between the sea level and 600 m (Childers et al., 1959), although cultivation systems do occur as high as 1100 masl in Mexico (Soto, 2003). In India, V. planifolia is reported to be cultivated up to 1500 masl (Anandaraj et al., 2005; John, 2005), and in Uganda, cultivation is successfully practiced between 800 and 1200 masl.
Light/Shade
V. planifolia demonstrates most vigorous growth under 50% shade. In dry periods with intense sunlight, it is preferable to use 50–70% shade (Hernández Medina, 1943; Ranadive, 2005) for better conservation of soil and air humidity. In rainy periods, the amount of shade should be reduced to 30–50% to avoid creating favorable conditions for growth of pathogens.
Excess shade causes weak growth and poor flower production, while excess sunlight leads to burning of the leaves and stems, as well as early fruit drop. Plants that suffer from either too much sunlight or shade are the ones most likely to develop diseases.
Site Selection
The first step in designing a successful vanilla cultivation system is to choose a site to plant.
The land destined to be used for the cultivation of vanilla (vainillal) should have an excellent drainage, rich humus content, and a pH between 6 and 7 (Childers et al., 1959; Soto, 2003; Ranadive, 2005); the land should receive morning sunshine and not intense rays during afternoon, which can lead to the sunburn damages on the leaves (Sánchez Morales, 1993; Curti, 1995; Soto, 2003). Limestone soils on slight slopes are the most appropriate substrates for cultivating vanilla because they tend to be less acidic and are well-drained (Childers et al., 1948; Bouriquet, 1954; Dequaire, 1980; Ranadive, 2005); acidic soils are the least recommended because they favor the establishment of fungal pathogens (Soto, 2003).