VANILLA GROWING IN UGANDA
SCIENTIFIC NAME: Vanilla planifolia
FAMILY: FAMILY: Orchidaceae
Whilst working in Uganda for the Uganda Development Corporation, one of my tasks was to develop a 24-hectare block of Vanilla. This is a semi-terrestrial orchid, Vanilla fragrans syn. V. planifolia, a member of the ORCHIDACEAE family. The sticks of vanilla you buy in the shop are the pods, which have to be cured after harvesting.
The object of developing the block was to get experience in growing vanilla on a large scale, and eventually to provide planting material for local African growers as another source of export income besides Robusta coffee. Hopefully, the plantation has survived the political upheavals of the past 20 years.
Management of the plantation involved a three-year rotation, i.e. crop for two years and rest for one, thus the area was split up into three eight-hectare sections.
TOP SHADE
Vanilla requires top shade. This was provided by Maesopsis eminii (RHAMNACEAE family) trees, known locally as "Musizi". These are tall, fast-growing African trees with straight lobes and a spreading canopy of small leaves which cast a light dappled shade, ideal for vanilla. These were raised in soil blocks and planted out 6m apart each way. They grew more than a metre in six months. The correct amount of shade is important. We found Vanilla is susceptible to too much shade, which tends to weaken the vines.
SUPPORT TREES
To support the vanilla vines, we grew Jatropha curcas (EUPHORBIACEAE) or Physic nut trees. The Vanilla roots attach themselves to the rough bark of these trees and draw nourishment from the organic matter and moisture in the bark. A vine in the fruit section of the Cairns Flecker Botanic Gardens can be seen with its roots attached to a palm tree. The Physic nut is a low-growing tree and easy to keep in check by slashing unwanted growth to regulate the shade. Thus the Vanilla vines had permanent living supports instead of white ant-susceptible posts, each tree supporting two vines, one on either side but not looped over into adjacent trees. These support trees were planted at 3m x 1m spacings.
We did also consider trying Casuarina as support trees without top shade, but the growth of the species we had was extremely vigorous in that climate and we feared that the trees might produce too much shade and become difficult to manage in time. The "Musizi" and Physic nut combination proved easy to manage.
PLANTING
Six-node cuttings are taken of mature vegetative wood - not from wood which has flowered. Two cuttings, one on either side, are planted up against the support trees with the bottom two nodes under the mulch - not in the soil, otherwise they tend to rot. If necessary, they can be tied with string to the support trees. Use a string which will rot, not plastic twine.
In the part of the country where we grew Vanilla and Cocoa, known as the 'fertile crescent' around the top end of Lake Victoria (Lake Amin) it rained just about every week. But under our conditions with our long dry periods, we would need overhead sprinkler irrigation. After planting, there is about a three-year immaturity period.
SLASHING AND MULCHING
Only slashing of the grass was carried out between the rows and the trash piled up against the bases of the vines. Vanilla roots, after having descended the support trees then travel along the surface of the ground beneath the mulch and across the rows under the mat of grass. Where trash was lacking we trucked in bagasse from local sugar mills.
In Uganda, cheap hand labour did the slashing and mulching, but under our conditions lightweight slashing equipment would be needed so as not to damage surface roots. Something like a four-wheel bike with wide flotation tyres pulling a separately powered or P.T.0.-powered twin-bladed slasher to throw the trash under the rows in one pass. Mulching must be thick enough to, hopefully, control all weeds - so forget Roundup®!
PRUNING
Shoots from the cutting eventually grow up through the support trees and become pendulous. Flowers form later from the axils of most leaves. The soft tips were removed near ground level. These were taken to the nursery and rooted under shade in bags filled with fern fibre to supply the out-growers.
After the beans were harvested, the stem which has borne the pods is cut back to a growth bud near the support tree and where there are plenty of aerial roots.
Vines were always pruned and pollinated according to their vigour. No weaklings were allowed to bear fruit. Only vigorous, healthy vines were brought into bearing, leaving only the amount of mature fruit wood that the vine is able to support. When pruning, one must always think one year to 18 months ahead, at least under Uganda conditions. That is for the growth to form, flower set and mature its pods.
POLLINATION
In Uganda, flowering occurred in March-June and September-October. There were no suitable pollinating insects or birds so this job was done by hand, one being employed almost full-time and with excellent results. Using a pointed stick, he transferred the pollen masses onto the surface of the stigma in each flower. 5-10 flowers per raceme are pollinated according to the vigour of the vine. After pollination, the pods took about six months to form.
CURING
The pods are ready for picking when the ends become slightly yellow. After picking, the pods were dipped in hot water at 65°C for two minutes. After draining, the pods were laid in lines on a cotton (not wool) blanket. We experimented and found a cotton blanket was best. The blanket is then folded over the pods and then rolled up. The rolls of blankets were placed on shelves in a dry, airy shed to allow the pods to sweat. The blankets were unrolled each day to expose the pods to the sun for a period of around half an hour. This was repeated until curing was finished. The whole idea is to retain the juices in the pods and not to desiccate them. Once cured, crystals of vanillin form on the outside of the pods which give off a pleasant vanilla odour.
After storage for a couple of months, the cured pods were packed in tin boxes lined with silver paper and sealed for export.
PESTS AND DISEASES
Nothing significant in Uganda. Minor problems such as snails were controlled with baits and ants with insecticide.
ECONOMICS
I can't remember the yield per hectare or the price we received in those days, but it was certainly profitable under our conditions with our cheap labour! According to H. F. Macmillan's Tropical Planting and Gardening 1991 edition, demand for Vanilla rose 10-15 years ago, the price rising from US$15 per kg to $120 per kg. The book quotes Vanilla as being one of the world's most profitable Agricultural Commodities.
About 18 months ago, I noticed that Vanilla was quoted at $48 per kg under market prices in the press. Macmillan's quotes yields of from 500-800 kg cured pods per hectare per year over a crop life of about seven years.
Taking the lower figure of 500 kg per hectare, and say $50 per kg, we have a gross figure of $25,000 per hectare. Not bad!
Using current technology, we should be able to improve both the yield and quality. Under our weather conditions, as well as irrigation, windbreaks would also be necessary. Based on my practical experience, I do not think it is sufficient just to plant vanilla in the rainforest and let it look after itself because of excessive shade. Too much shade I found was very detrimental to Vanilla.
Anyway, if you want to have a go at growing Vanilla, I wish you the best of luck.
DATE: July 1992
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