Immediately following hand pollination, pollen tubes begin their germination and growth and eventual fertilization of the ovules. The ovary quickly begins to enlarge and assume a strong, dark green aspect as it orients itself downward. The maximum length and diameter of the fruit is achieved 45 days after hand pollination (Figure 6.6). Thereafter, growth ceases, and the fruit enters into a period of maturation lasting roughly 7–8 months.
FIGURE 6.6 Time-series data on the development of a fruit from V. planifolia cv. mansa (length and diameter) observed at the Ixtacuaco experimental station (INIFAP, Mexico).
Harvest
Vanilla is harvested when it reaches its commercial maturity, when the distal point of the fruit changes from green to yellow (Figure 6.7), generally 8–9 months after pollination.
FIGURE 6.7 Commercial maturity of green beans (8–9 months after pollination).
Early harvested fruits weigh less, are more susceptible to fungal attack and, when cured, yield smaller quantities of vanillin (Tiollier, 1983). Fruits that are harvested past nine months begin to dehisce, and change from green to yellow to dark brown or black. These fruits are called “splits” and have less value.
Northern hemisphere countries have harvest seasons from December to February while Southern hemisphere countries harvest from June to September. Most vanilla growers harvest at only one time, and collect all fruits, that is, those that are mature and those that are still developing. The still developing fruits dehydrate faster than mature fruits during curing. Some growers, for example, in Uganda and French Polynesia, harvest only when fruits are mature, generally once a week, prolonging the harvest to 2–3 months.
In Mexico, the whole bundle or raceme of fruits is harvested with the central stalk, or rachis, still attached. A more ideal practice is to harvest each mature fruit individually. Harvested fruits are placed in baskets or plastic crates to prevent mechanical damage, which can lead to pathogen infection. The fruits are also kept in well ventilated and shady areas.
After harvesting, it is customary to prune shoots that have already flowered. These shoots will not produce again (or as much) unless they retain buds. The pruning is performed with a knife or blade that is disinfected prior to use in a solution of 1 part bleach to 6 parts water.
The removal of these “spent” shoots serves to eliminate unproductive parts of the plant that occupy space and take away the energy resources from the plant. Their removal facilitates the maintenance of adequate ventilation and light conditions for the plant. Some of these spent shoots may serve as cuttings to start new plants if they retain meristematic tissue.
Yields from vainillales are extremely variable, and depend on the ages of the plants, density of the plantings, method of cultivation (“traditional” or modern), source of water (rain-fed or irrigated), the soil and climatic conditions of each site, and so on.
Worldwide, average yields of green vanilla are less than 500 kg/ha, since most growers employ few technologies. Those who use technologies for irrigation or fertilization or use shade houses may obtain 3–4 tons of green vanilla/ha, or approximately 500–800 kg cured vanilla/ha (Ranadive, 2005).
The average weight of fruits per plant is 1–2 kilos and up to 5.5 kilos for plants that have been grown on orange tree supports (Lopez Méndez and Mata García, 2006).
In whatever system of vanilla cultivation, the maximum yields occur in the fourth or fifth year following planting (second or third harvest). After this time, production volume can be lower or higher, but after nine years yields steadily decline until productivity ceases almost completely by the twelfth year.
Experience has demonstrated that vainillales that are densely planted can produce high yields, but generally only once. Later, yields decline drastically and abruptly terminate usually six years after planting because of major problems with disease. In vainillales that are less densely planted, a productive life span of 12 years is expected because adequate parameters exist for ventilation and disease/pest prevention. The best model for this is vanilla cultivated on orange supports.
Labor Requirements
Vanilla is a labor-demanding crop, requiring 172–575 workdays/year ha depending on the system of production, and stage of the plants (i.e., vegetative growth versus productive). The fourth and fifth years are normally the most demanding since production is greatest then. In Mexico, in the semi-intensive system using Erythrina sp. as a support tree, growers have needed a maximum of 575 workdays over the year (on an average, it is 316.2 workdays).
The majority of workdays, more than 50%, are needed for hand pollination, followed by shoot management (looping and rooting, 10.4%), pruning (7%), and weed control, accommodation of organic materials/compost, and phytosanitary maintenance (7%) (Table 6.1).
Labor requirements are similar in other systems of vanilla cultivation. One family can cultivate a maximum of 1 ha of vanilla, but needs to contract wage labor for help with pollination in a larger area.
| Activity | No. of Workdays | Percent of Total |
|---|---|---|
| 1. Pruning | 40 | 7.0 |
| 2. Composting | 20 | 3.5 |
| 3. Mulch acquisition | 20 | 3.5 |
| 4. Irrigation | 10 | 1.7 |
| 5. Weed control/mulch maintenance | 40 | 7.0 |
| 6. Shoot management | 60 | 10.4 |
| 7. Pest/disease control | 40 | 7.0 |
| 8. Hand pollination | 300 | 52.1 |
| 9. Harvesting | 30 | 5.2 |
| 10. Inspection/removal of diseased plants | 15 | 2.6 |
| Total | 575 | 100 |