Handbook of Vanilla Science and Technology

The first yields from shade houses have been variable, with the maximum thus far being 514 kg green vanilla per 1,000 m², from 1,524 vanilla plants. This value theoretically scales up to 5,140 kg green vanilla per ha, similar to yields obtained from shade house production systems in other countries.

Growers agree that shade houses provide for a system of better care and overseeing of vanilla plants, which tend to grow vigorously as a consequence. However, it is yet to be determined what the real outcomes and economic viability of this system of production are.

In whatever system of vanilla cultivation, the maximum yields occur in the fourth or fifth year following after planting (second or third harvest). After this time, production volume can be lower or higher, but after 9 years, yields steadily decline until productivity ceases almost completely by the twelfth year.

1.3 VANILLA PROPAGATION TECHNIQUES

Vanilla is propagated almost entirely by stem cutting. The cuttings are procured from another grower or from a government agricultural entity. Cuttings are made from highly productive and vigorous individuals that have never produced fruits. The cutting itself should not be a flowering shoot and should have at least 3 nodes with viable axillary buds for producing new shoots from which the plant will grow. Cuttings should be free of damage or symptoms of pests/diseases so as to avoid future proliferation of disease. A best practice is to ensure that the cuttings are certified as virus-free. Cuttings are normally 6 to 8 nodes (80-20 cm long, 1 cm in diameter) in length. Longer or thicker cuttings form new vegetative and reproductive shoots more rapidly (Ranadive 2005), but are more difficult to deal with during planting, and are more expensive.

1.3.1 Preparation and disinfection of cuttings

Cuttings are prepared prior to planting. The three most basal leaves are removed by hand by twisting at the petiole and taking care not to tear into the stem where open wounds can facilitate the spread of pathogens.

In order to prevent stem rot, caused primarily by F. oxysporum, stem cuttings are disinfected prior to planting. The basal portion of the cutting is submerged for 2 to 5 minutes in a fungicidal solution. The solution may consist either of carbendazim (2 g/L) or Bordeaux mixture (1 kg lime + 1 kg copper sulfate in 100L of water), the latter being less effective but authorized for the production of organic crops. Fungicidal solutions are handled with rubber gloves to avoid harmful exposure to the body.

After disinfection, cuttings are hung separately on a structure 1 to 1.5 m tall, in a shaded and well-ventilated area for a period of 7 to 15 days. The cuttings slightly dehydrate allowing for more flexible material for planting. Calluses form over areas of the cuttings that were damaged during leaf removal.

1.3.2 Establishing cuttings - timing

Cuttings are planted when support trees have developed sufficient foliage to prevent the young vanilla plants from being burned. With shade cloth, cuttings are planted immediately after the establishment of support trees. The best conditions for planting cuttings are in humid substrates during warm, dry months preceding the onset of the rainy season (Ranadive 2005). This timing favors a high percentage (> 90%) of successfully established cuttings, since high temperatures are conducive to the emergence of new shoots and roots.

1.3.3 Establishing cuttings - planting

Cuttings are planted in the following manner. Adjacent to the support, a shallow ditch is dug 5 to 10 cm deep, into which the cutting is placed horizontally (but only the part that has had the leaves removed). The cutting is then buried with 3 to 5 cm of organic material and/or fertile soil or leaves, which will serve as a mulch and as a source of nutrients. The extreme basal end of the cutting (2-3 cm) is left uncovered to prevent rot (Wong et al. 2003; Ranadive 2005), especially when the substrate is humid. Some cuttings are established without making ditches, and are simply placed on top of a humid substrate.

Once planted, the rest of the cutting (with leaves, ca. 4-5 nodes) is positioned vertically on the support and fastened with bio-degradable material such as banana leaves, tree bark, or henequen fiber.

Under optimal conditions of humidity and temperature, and with vigorous, healthy cuttings, the first roots begin to emerge the first week after planting and the first shoots in about 1 month.

1.3.4 New bud formation and root growth

Warm temperatures stimulate both bud break and the longitudinal growth of shoots. In Mexico, most vegetative growth occurs in spring and summer (58-67.8 cm/month). In fall and winter, this rate of growth declines to 22 to 52.2 cm/month.