AFRICAN

ORCHIDS

Cultivation of Bulbophyllum
From the point of view of cultivation, Bulbophyllum is like most other genera - same species are reliable, easy to grow plants, whilst others are practically impossible to keep alive for any reasonable length of time. It is difficult to fathom why this should be so, and there are often no obvious reasons why, for example, two species which share the same habitat, and may even grow in close association, will behave quite differently from one another in cultivation.
Generally speaking, most Bulbophyllums enjoy moist, humid and protected conditions, and in cultivation these preferences should be observed. They have relatively thin, short and -unbranching roots, features which indicate an intolerance for dry conditions, especially for any extended period.
Of course, this varies from species to species, although those from high rainfall areas may require daily watering throughout the year, particularly when grown as slab plants.


Relatively cool conditions are also beneficial to most Bulbophyllums. Even in the tropics, most species occur in mountainous highlands, where the environment remains fairly cool and damp for much of the time. Regular, year-round rain-fall, as well as frequent fog s and mist, sustain the orchids inhabiting these forests, and although many species are able to tolerate reasonably bright level s of light, they dislike heat, and will suffer if temperatures get to high.
In the warm, lowland tropical rainforests, conditions remain fairly constant throughout the year, and there are seldom extremes of high or low temperatures. Average temperatures are certainly much warmer than elsewhere, and winter-time minimums would only occasionally and briefly drop as low as 15°C. Protected by the jungle canopy, and nurtured by constant humidity, the truly tropicaI species enjoy an insular environment, and maximum temperatures during the warmer months may be 6°-8°C cooler within the rainforest than outside it.
Because of their rambling or pendulous habits of growth, many species are cultivated on slabs, which allow plenty of room to move. It is often surprising to see how much living plant material can be accommodated on a single slab, with the orchid growing up and down, over and around, and sometimes completely obscuring the underlying slab.


Tree-fern fibre is the most successful and commonly used slab material for most species. It is free draining, but will retain same moisture between waterings. Probably the best tree-fern fibre is that obtained from Cyathea australis, commonly known as the rough tree fem. The fibre obtained from the thick, buttressed trunks of this species is known as hard black tree-fern fibre. Because of its tight, rigid structure, it can be cut into relatively small pieces and still maintain its structural integrity, or be left as bigger slabs for the larger growing species.
Soft brown tree-fern fibre from Dicksonia antarctica is also useful, although the roots of some species are unwilling to penetrate this type of tree-fern fibre, perhaps because it is too naturally acidic. Also, soft brown tree-fern fibre can be quite moisture retentive, and watering needs to be closely monitored to avoid constantly wet conditions. However, for some species it makes an excellent host.
Slabs of natural cork bark also figure strongly in the culture of Bulbophyllums, and orchid roots usually take readily to cork. However, it is not very moisture retentive, and this factor usually means extra watering is required. A number of other slab mate-rials have been used by growers with varying degrees of success s, and these include weathered hardwood (good for B. globuliforme and B. minutissimum), coconut husk, lengths of natural timbers and ironbark totems. All are worth a try.


In recent times, some growers have taken to cultivating their slab plants in a horizontal position on the bench, rather than vertically on a mesh frame. This method is especially useful in the early stages of establishment, when the plant requires extra moisture around its roots and rhizomes to avoid dehydration. After 12 to 18 months, most species treated in this way will be well established, and they can then be positioned on an upright frame in the regular manner. However, there are a few species that really do regent any drying out, and these are best left in the horizontal position permanently.
Whereas Bulbophyllums have conventionally been grown as slab plants, many of the larger growing species have proven quite amenable to pot culture. A fairly fine grade potting mix is required, usually consisting of 60% fine pine bark, 20% small pebbles, 10% perlite and 10% chopped sphagnum mass, or something similar. Due to their relatively short root systems, only shallow pots, or squat pots, are required for most Bulbophyllums. Because of the extra watering generally required for the successful culture of these orchids, the fine mix will tend to break down more quickly than normal. About three years is the life expectancy, and repotting should be carried out before the plants begin to deteriorate. Sphagnum mass also makes an excellent potting medium, either on its own, or combined with polystyrene beads. Use only fresh, top grade sphagnum for the hest results. Do not pack it too tightly into the pots, do not use fertilizers on it, or the surface will become slimy with algae and impede air flow through the pot, and do not neglect regular repotting.


Sphagnum moss breaks down after 18 - 24 months, at which time your plants should be repotted into fresh sphagnum. The best way to remove spent sphagnum from the roots of the plant is to rinse it out in a bucket of water, and then carefully pull away the strands, while continuing to rinse.
Hanging baskets are also used successfully for Bulbophyllums. Wooden baskets are probably hest, as they allow the plants to ramble across the surface, and then down and around the sides without any impediment. For larger specimen plants, wire baskets may be required for extra capacity, and these also work quite well, although a larger grade of potting mix should be used in the bottom of the basket. A piece of shade- cloth, trimmed to fit the basket, will hold the potting mix in place, and yet still allow good drainage and air movement.


Even many of the tropical species may be grown without artificial heating during winter in the southern states, as long as they are provided with protection from frost, and as slab plants they take up little space in the orchid house.


Interest in Bulbophyllums is at an all-time high, with many enthusiasts specializing in these orchids. The diversity of floral form never fails to fascinate, with a seemingly endless array of dramatic shapes, bizarre appendages and striking colours and colour combinations. Same of the perfumes are interesting as well. They really are wonderful plants, with species for all seasons and all tastes.