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|Vol. 10(5), pp. 2-6||The McAllen International Orchid Society Journal||May 2009|
Vanilla is the only orchid to provide a fruit edible to humans and in doing so consistently provides its grower a wealth of challenges. Its production ranks with the most time consuming of the worlds spices for the many steps it must undergo before use; from hand pollination of the ephemeral flower to on-the-vine ripening of seed capsules that later become the repository of the vanilla flavor as we recognize it.
Vanilla is a genus of over 110 members with one of the most commonly proliferated species being the Vanilla planifolia or Flat-leaved Vanilla. Native to Mexico, species of Vanilla thrive particularly in the twenty degree band North and South of the equator which extends from mid-Mexico and into the northern half of South America as well as into Madagascar, the island of Tahiti, Puerto Rico and other moist tropical climes.
Fig. 1. Pl. 170403-21. Vanilla planifolia, in JWT greenhouse. Digital photo: 16 April, 2009.
A striking terrestrial plant, Vanilla planifolia is a thick waxy vine 1 to 1.5 cm in diameter and smooth 3 to 4 cm wide, 9 to 15 cm long tapered leaves that grow alternately every 4 to 7 cm (Fig. 1). From the abaxial (underside) of each leaf growth may emerge one or several tendrils that anchor the vine steadfastly to the growing surface.
Fig. 2. Frontal aspect, flower, V. planifolia. Digital photo 16 Apr 09, 1130 hours local time.
The flower itself is not as ornate as a typical show orchid, but with a 6 cm span and the blooming life of dawn to dusk they are a spectacle nonetheless. They emerge as a raceme of buds and bloom at a rate of nearly one per day, the outermost ring maturing and blooming and continuing upward on the raceme. The flower itself will open shortly before sunrise and achieves maximum bloom by noon after which it begins to wilt as night progresses (Fig. 2). If the flower in not pollinated within the window between bloom and nightfall, it will shrivel and drop off the plant, typically by the next morning. This combined with the presence of a trap door betwixt the male and female parts of the flower assure that in the wild the probability of pollination, even in its native habitat rife with stingless bees, is at or less than 10% (Withner, 1959).
A few basic methods of hand pollination detailed in the last 50 years of orchid literature were available. Two are the most prominently used in modern production, and are quite similar, but differ by either pinching off the pollinia from the hinged tip of the anther (Fouche and Coumans, 1992), or letting it be, and--instead--lifting the rostellum that separates the two, and pushing the organs together (Arditti, 1992).
Fig. 3. V. planifolia, raceme, profile of flower, & blossom assumed pollinated. Digital photo 18Apr09.
Fig. 4. Column, flower, V. planifolia. 18 APR 09
Fig. 5. Anther & Pollinia, V. planifolia. 18 Apr 09.
Personally, I approached the Vanilla planifolia plant hands-on; armed with a toothpick and a line drawing detailing the anatomy of this peculiar flower (Fig. 3). The John Wayne Trail Nursery greenhouse as of April 16th had two vanilla plants in flower, each having grown at least 5 foot from a hanging pot, up a tree fern material and continued growth draped over a steel support. The first action was to pull back the sepals of the flower and gain access to the column which, in orchids is the tubular organ housing both sexual organs (Fig. 4). At the distal end of the column, the hinged anther loops downward to hold the pollinia to the roof within the column. The toothpick was looped in under the hinged anther, and pulled straight outward to show the dual pollinia cluster visibly ripe with bright yellow pollen (Fig. 5).
Fig. 6. Pollinia. 18 Apr 09.
Fig. 7. Anther, base, rostellum, & stigma. 18 Apr 09.
A light pinch with thumb and forefinger detached the pollinia from the springy hinge of the anther (Fig. 6). Squeezing the pollinia cluster lightly pushes the pollen grain onto the fingertips and the now free toothpick can be moistened with a bit of saliva to scoop the pollen onto its tip. Repositioning one's hand and offering the free end of the toothpick to the flower, this tool was now utilized to lift the rostellum which is springy and cups over the top of the stamens. Once lifted, the toothpick is flipped around, rostellum held in place with the thumb, and the pollen gently twisted into the ample round opening of the stigma (Fig. 7).
Fig. 8. Part of raceme and browned flower at eleven days post-pollination, V. planifolia. Digital photo 27 Apr 09.
With the mechanics of the pollination completed, it is merely a matter of waiting until signs appear that fertilization has occurred. The flower should stay intact and one should be able to notice a pregnant droop to the pollen tube going back to its peduncle link to the raceme. Over the course of 11 days the first flower pollinated browned and developed a very noticeable bend (Fig. 8). Hopefully the few centimeters inferior to the flower will develop from a slender ovary to a capsule of between 7 and 20 cm, rewarding our efforts with a Vanilla planifolia fruit.
Many variables present themselves at this juncture. Popular literature puts the time of maximum fertility at anytime between blooming (0500-0600) to midday (1100-1200) before the flower atrophies. Clinically, I used the pinch-and-pollinate-toothpick method on 13 flowers, between 1130 and 1155 hours. The result has been six successful pollinations, with the flowers holding and drooping pendulously with the newest pollination attempt having occurred 36 hours prior. A success rate of just less than 50% is considered not overly unproductive for an amateur pollinator in an otherwise pollinator free environment.
At this point the work has merely begun. It takes 5-6 weeks for the capsule to mature (Arditti, 1992) and can take as long as 9 months for the "bean" to sweat and ferment before it even resembles vanilla. According to the Tahitian methods of sweating, (Fouche and Coumans, 1992) the beans are wrapped in cloth and sun dried for an hour or so during the day to purge moisture, and at night they are kept in wooden boxes to ventilate them and further concentrate the vital compounds of the bean.
Fig. 9. V. planifolia flower, dissected and parts noted. Digital photo 28 Apr 09.
Still, questions remain. Why after numerous years of growing and viewing the Vanilla orchid (Fig. 9) has this been the only session of budding and blooming seen by Trail Nursery's resident orchidologist R.J. Ferry? Reference is made (Withner, 1959) to a technique used by modern cultivators to provoke the budding of vanilla orchids that forces the vine to bend over a support to not only put the top at a reachable height for pollination but also to break the straight upward growth. This has taken place inadvertently in our greenhouse with both plants, both surprisingly coming into season together and producing racemes in unison. Withner proposes that it is the action of a carbohydrate buildup below the bend of the vine that spurs the growth of a raceme inflorescence from a normally leaf producing meristem, and he notes that this method has been successful in triggering a predictable flowering season in commercial vanilla production. Another variable concerns the soil moisture as Withner very aptly draws a connection between dry warm winters having correlating with successful blooming and appreciable yields. Was the blooming triggered by lessened watering during the winter months? From late October, 2008 through March, 2009 the area experienced a severe drought. Might the outside overly dry conditions have had a significant effect on this green-housed plant? Was the plant induced to flower by bending of its growths which inhibited its straight upward course? There appears to be many still unanswered questions!
One doubts that his first experiment into vanilla production will be fruitful, but I remain eager to see the ovaries bulge and turn into pods bursting with tiny seeds that in turn flavor an iced tea or tub of hand cranked ice cream. Sweet vanilla, see you in 9 to 14 months!
Arditti, J. 1992. Fundamentals of Orchid Biology. New York: John Wiley & Sons. 691pp.
Vanilla--The Orchid of Commerce. C.L. Withner (pp. 477-508) in Withner, C.L. ed. 1959. THE ORCHIDS A Scientific Survey. New York: The Ronald Press Company. 648pp.
J.G. Fouche, J.G., and M. Coumans. 1992. J.G. Coumans and M. Coumens summarize four techniques for pollinating Vanilla planifolia. AOS Bull. 61(11): 1118-1122.
Ashley, J. The Culture of Vanilla planifolia in Uganda. AOS Bull. 45(4): 291-296.
Cruz, M. de la and J. Badianus. 1940. The Badianus Manuscript (Codex Barberini, Latin 241. Vatican Library). Baltimore; The Johns Hopkin University Press. 118 facsimile colored plates from original ms. and 4 other plates 4to, pp. xxiv, 341, cloth. An Aztec herbal of 1552.
Miller, M.A. 1959. Orchids of Economic Use. AOS Bull. 28(3): 157-162.
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Williams, L.O. 1951. The Orchidaceae of Mexico. CEIBA 2:1--321 plus index.