In my earlier article on ‘Khaya: The wonder tree for commercial cultivation,’ I discussed the growing and uses of Khaya timber.
Now, having constructed a timber floor in a house with timber harvested from my own garden, I have been fascinated with the outcome and realized the future potential of Khaya and wish to share my experience with the readers.
I had a number of mature Khaya trees in my garden and the decision to use Khaya for flooring was solely based on information over the internet that, in the past, Khaya timber from West Africa was exported to Europe for flooring and furniture to the extent of causing near extinction. Khaya is used locally in the furniture industry and sold to customers as mahogany, but there was no report of Khaya being used locally for flooring.
Khaya in Sri Lanka
Out of the seven varieties of Khaya, the most valuable variety is Khaya Senegalensis, generally referred to as “African Mahogany” which is a tree similar to Mahogany natural to Africa and Madagascar. The tree was introduced to Sri Lanka several decades ago by the Forest Department, but the Department failed to educate the prospective end-users of the timber.
A large number of Khaya trees planted by the Forest Department exist by the roadside in the Kurunegala district. Mature Khaya trees can be seen along Kandy road near Kegalle, and also near Batticaloa town. Between Dambulla and Habarana, extensive young plantations exist by the roadside.
Khaya is a fast-growing tree, reaching a height of 100 feet and a diameter of three to five feet. It yields timber similar to mahogany, but the timber is heavier. In Sri Lanka, Khaya matures in a mere 10 to 12 years, whereas mahogany requires 20 to 25 years. A young Khaya plant develops a deep root system within its first year, making it drought resistant. Therefore, it can be successfully cultivated throughout the low regions of the country, and thrives in wet as well as dry zones, even in poor soils, but not near water.
Khaya timber has been exported from West Africa (Gambia) to Europe since the first half of the 19th century. In Africa, harvesting of natural Khaya has been so heavy it has led to the threat of extinction. Khaya is considered a vulnerable species and has been included in the ‘IUCN (International Union for Conservation of Nature) Red List of Threatened Species’.
Khaya, physical properties
Khaya timber had been described as “Colour varies from light pinkish-brown to deep reddish shade, often with a purple cast. Khaya/African Mahogany is a hardwood with an interlocked or straight grain, often with a ribbon figure, and a moderately coarse texture. Colour ranges from creamy-white sapwood to reddish-brown heartwood, often with a purple cast. African Mahogany is moderately heavy and with medium bending and crushing strength, low stiffness and shock resistance, moderate decay resistance, and good stability.”
Sawing, treatment, and drying
At harvesting, my Khaya trees were 12 years old, nearly 60 feet in height and at four-foot height were around five to seven feet in girth. After cutting and transporting trees to the sawmill, the mill owner wished to leave the logs to dry for nearly a month. The logs were sawn with a horizontal saw, the flooring planks just over one inch thick and six inches wide; the balance into various sizes depending on my requirement.
After sawing, the timber was in storage for nearly three months for air-drying and was transported to a treatment plant. At the treatment plant timber was placed in a long steel cylinder and sealed. The cylinder was first vacuumed to reduce moisture content in the timber and thereafter, impregnated with a boron-based chemical solution under pressure. The boron treatment is expected to make the timber resistant to insect and borer attack, although Khaya is supposed to be resistant to borer and white ant. Next, the treated timber was transferred to a drying kiln; the drying operation took nearly 10 days.
Converting to flooring planks
To modify treated planks into fixable flooring planks, they need to be converted to identical thickness and width, bottom leveled, top planed and sides be tongue and grooved. The entire conversion was done in a timber workshop in Panadura, in a large machine nearly 30 feet long in a single operation, which ensured every single plank is of exactly the same dimension. The planks were to be fixed on to a 2”x2” timber support, also of Khaya, treated, planed and sized by the same machine which tapered the top to just over an inch.
Floor preparation and installation
In the floor preparation, the ground was treated with an anti-termite chemical, compacted and was laid with a layer of concrete. The concrete after hardening was perfectly leveled with a layer of cement, sand mortar. The modified 2”x2” timber was placed on the leveled surface at one-foot intervals and was concreted leaving half-inch to the top. The heavier bottomed timber was anchored to the floor with concrete. The half-inch gap between the concrete top and the flooring plank would give a hollow sound when stepped upon.
When the concrete has hardened, the anchored timber was ready to accept the timber planks. The tongued and grooved planks were nailed to the anchored timber, ensuring nail heads were well sunk into the plank. The procedure should be precise and needs to be carried out by skilled workmen; otherwise, gaps would appear on the floor.
Leveling and painting
The completed timber floor had a slightly uneven surface and was cut and leveled with a specialized machine. The completed floor clearly showed the grains on the Khaya planks.
To safeguard the surface against scratching and damage, the timber floor needed surface treatment. I selected an advertised brand, with a clear finish without any dye that was comparatively more expensive than varnish and applied three coats as recommended. The first coat got absorbed into the wood immediately on application but improved the appearance. The second coat further improved the appearance and the final coat brought some shine and highlighted the grains of the Khaya timber.
I was completely amazed at the enhanced grain appearance on the timber and am extremely satisfied with the final outcome. The clear finish without any dye showed the fullness ingrain in the timber and the contrast from one plank to the other, which could only be highlighted on a timber floor, demonstrated the reason for the high demand for Khaya in Western countries.
Khaya for furniture and flooring
Upon harvesting, Khaya wood is pale in color compared to mahogany, but with the passage of time, Khaya becomes darker and does not require dyeing. However, different sections of the timber would differ in color and texture, and would not be acceptable in the furniture industry without dyeing. But this very fact makes Khaya an excellent flooring material.
Earlier, when I harvested a 10-year-old Khaya tree, the sawmill owner was skeptical of the quality. But having sawn the logs, he was surprised at the hardness and difficulty encountered in sawing. Carpenters complain that Khaya timber is tough to work with, due to the interwoven grains which make the timber resistant to wear and tear. Although Khaya timber is supposed to resistant to borer and termite attacks, in my construction I treated the timber to be on the safe side.
Khaya flooring for export
The fast-growing Khaya could be commercially cultivated, converted into flooring planks and could find a ready export market in developed countries, which used Khaya flooring over the centuries. Converting timber to flooring or marketing would cause no problem, but timber needs to be available in large quantities to sustain a market.
Growing of Khaya
Similar to mahogany, Khaya is expected to produce flowers and seeds for propagation. I had over 10 Khaya trees, some over 12 years of age, but did not come across any fruits. The Forest Department had been importing seeds for their plants and I am not aware of locally-produced seeds. Perhaps the humid climate in Colombo District may be non-conducive for flower and fruit formation.
Most lands at low elevation throughout the country would be suitable for Khaya. Even in Colombo District, former rubber plantations, which have been abandoned due to labor shortage and low commercial value due to distance considerations, could be cultivated with Khaya. Rubber plants become ready for tapping after six years, but proper yields take eight years; whereas Khaya matures in 12 years, with minimum maintenance in pruning excess branches, would be an attractive alternative under the current labor shortage.
But the biggest barrier would be the availability of seedlings for planting. The Forest Department produces only a limited quantity of plants with expensive imported seeds. The answer would be a tissue culture.
Plant tissue culture
Plants have a special ability where a small part of their body can grow into a complete plant: for example, a bud or a root through proper cultivation. Usage of this special characteristic of plants for large-scale seedling production is known as plant tissue culture technology and has been practiced for nearly a century. The tissue culture technique helps to develop plant sections under sterile conditions on a nutrient medium, in order to produce clones of a particular plant, maintaining the same properties of the mother plant.
The procedure involves the following steps. First, tissue samples are scraped from the parent plant and transferred to plates containing sterile agar jelly cells that multiply rapidly into small masses of plant tissue. In the next phase, the plant material is re-divided and placed in a medium with plant growth regulators that induce the proliferation of multiple shoots. This process is repeated many times until the number of plants desired is reached.
Thereafter, in the root formation phase, hormones are introduced to induce rooting and the formation of complete plantlets. When plant cells have grown until they have recognizable roots and leaves, the plantlets are transplanted into potting trays with compost, where they develop into plants.
Tissue culture produces new plants exactly like the original mother plant, maintaining quality and uniformity over a short period of time. Plants are characterized by disease-free growth, are more fibrous, with healthier root systems, and have a higher survival rate.
The techniques of tissue culture had been practiced in Sri Lanka for decades. Years ago, CIC produced potato seedlings under tissue culture techniques and was distributed as planting material replacing imported seed potatoes. Local production of large quantities of Khaya plants for local cultivation would enable the establishment of large-scale plantations at a reasonable cost, for the production of quality timber for local furniture and export as a flooring material.
Research responsibility
Multiplication of plants with tissue culture technology could be carried out by the private sector (for commercial purposes). In addition, the research could be conducted by government organizations like the Forest Department and the Universities of Ruhuna, Rajarata and Eastern, whose location and climatic conditions favor large scale cultivation. For universities, the research could commence with Khaya and be extended into other areas.
The country’s fruit supply depends mainly on home gardens, whereas countries as Thailand possess large extents of commercial plantations producing fruits on smaller trees, but yielding prolifically. Locally, good quality, reliable plants are almost unavailable and most purchased plants for home gardens, after years of care, turn out to be those of low yield or different to intended plant type.
Technical details
For those interested in the technical details of Khaya timber, could be got from a document produced by the Australian Government under ‘Evaluation of the Wood Quality and Utilisation Potential of Plantation grown Khaya Senegalensis (African Mahogany)’.
The report offers details of merchandising log volume, log physical properties as density, hardness, heartwood/sapwood proportions, sawing behavior, recovery, drying properties, shrinkage, termite resistance, gluability, marketing requirements as to colour, texture, grain, figure and other information that would be useful for a potential exporter.
Commercial cultivation
Agricultural laboratories should be encouraged to undertake large-scale production of high-quality Khaya plants with tissue culture techniques for the anticipated market. Searching “tissue culture” over the internet illustrates diverse works carried out the world over and opens up enormous potential and opportunities in fruit cultivation and in floriculture, which would present employment opportunities.
The increasing prices of high-quality timber for furniture, house construction, and possible exports would continue to increase the demand for timber. Currently, large quantities of timber are imported and the exporting countries would not be able to continue forever. The short growing period of mere 12 years, the shortest time period for any timber variety, would enable a quick return on investment.
There would be a ready market for the produced timber and those hoping to enter the export of flooring or veneer market should study the Australian report carefully. The study gives details of market requirements, which otherwise the exporter/grower would have to learn the hard way. Especially note the value of avoiding knots in timber, resulting from branches during the growing stage that could be avoided by regular pruning during early growth.
The cultivation of Khaya with tissue cultured plants could open a new frontier in the cultivation, production, and export of timber flooring and veneers for the private sector, especially in abandoned/partially cultivated lands in labor deficient regions.
The tissue culture laboratories could advance themselves into other sectors as fruit and floriculture, in producing quality fruits for local and export markets, and replacing large quantities of flowers that are imported, especially to the hotel sector. Growers suffer from a deficiency in high-quality planting material and fulfilling their requirements would open a new chapter in the country’s agriculture.