RECENTLY there was an international orchid exhibition which brought experts to Kuching. They also brought in all these lovely plants from various parts of Asia. These plants were raised beautifully through much tender care. This week, let’s get back to the basics of how to ensure a successful orchid garden.
SWEET: A purple Cattleya orchid.
Remember that orchids are actually wild plants from the jungles where light and weather conditions are very different from urban settings. Orchids are neither parasitic nor carnivorous. They need a continuous supply of fresh air, diffused light and some water. The temperature is best around 28 to 30 degrees Celsius.
We tend to believe that orchids dwell on trees but there are also many terrestrial orchids such as cymbidiums and cypripediums that grow naturally on the forest ground, while some actually thrive on bare rock crevices. I know some locals and foreigners who seek out new mother plants in our jungles. Trees in the jungle provide good growing conditions of fresh air, sunlight and even protection from being eaten by animals when the orchids grow above ground level.
It was not until hobbyists grew orchids artificially in temperate countries in the 19th century that skills and botanical knowledge grew of the correct conditions to keep plants successfully. Many would keep the secret formulas to themselves for business gains. It was not until Sir Joseph Paxton came up with a cool, clean and open to air and sunlight greenhouse for orchids that household growers could successfully cultivate orchids in temperate countries.
This technique was adopted by scientists and growers doing tissue culture, hybridisation and cross-breeding. From then there developed proper gardening techniques, which we can now use at home. In reality, most local orchids are not too difficult to grow. What’s a bit more difficult is to get them to flower.
Carl Linne – the father of botany who first established the binomial system of plant classification – recorded some 100 species of orchids in the 18th century. Now there are more than 16,000 distinct orchid species.
High altitude orchids found above 5,000 feet, like cattleyas and Odontoglossums, require the temperate climates of great mountain ranges. Oncidium nubigenum or orchid of cloud is found at snow level high up in the mountains. So the requirements of orchids depend on where they originate from.
Growing requirements
Water – When watering orchids, we need to remember the fact that under the aerial root system, water is best applied with a spray or mist sprinkler system. Do not over-water them because if air is restricted in the root-sphere, rotting can occur.
Light – Light requirements for orchids are variable from tropical heat to the cool jungle environment according to the species. This is the chief consideration for greenhouses and outdoor growing. As a simple rule, check with your supplier on the needs of shade and darkness or else place them under the car porch or a tree.
Nutrients – As chemi-culture plants in greenhouses, orchids may not need as much nitrogen as other plants or the leaves would be dark green but limp. Foliar sprays are best applied during the cooler part of the day to allow more absorption. Slow release fertiliser may scorch or burn the tender new roots. A water soluble formula fertiliser is recommended as it can be washed off and re-applied in two to three weeks. The best time to apply is during the active growing period. There are a lot of fertilisers for orchid growing in the market. We should also not forget to use hormones to initiate flowering and growth.
Potting mix – Orchids need a good water-retaining medium like charcoal, coconut husks, bracken sheet lining, tree fern bark or sphagnum moss. These offer the best aeration and do not retain too much water to cause root rot. Charcoal is also useful to absorb toxic substances, while brick pieces provide good drainage along with vermiculite, perlite and larva rocks. The ideal combination of the above organic and inorganic items will depend on the species of orchid itself.
Pests
This is the most problematic for amateur growers as pests may attack not only the leaves, stems and roots but also the beautiful flowers. Those orchids on display at shows have been selected from farms, so you only see the best. Get rid of ants that carry along aphids, mealy bugs and scale insects. Aphids and scale insects must be tackled early by physically removing them. Red spider mites are real problems as they are small and not easily noticed until the bad effects like yellowing or curling of the leaves occur. Snails and slugs eat away portions of leaves and even the young shoots and buds. To control them use metaldehyde snail bait. The worst of the pests are weevils and beetle larvae that bore into the stem. Control using pyrethrum and other pesticides.
Diseases and disorders
There are several pathogens that are difficult to control from the common bacterial leaf rot, root rot and crown rot to virus colour break in orchid flowers. Leaf rot would start after constant rainy weather when the bacterial spores land on the tender leaf surface and germinate as tiny spots that gradually spoil the surrounding cells by turning them yellow. Rotting can extend to the rest of the leaf causing overall damage if not controlled early. The best solution is to cut away the diseased portion of leaf.
Crown rot is most damaging as it kills the growing tip or meristematic cells of the whole shoot or branch. There is little chance you can save the growing tips once this happens. Control watering and do not wet the top shoots to prevent water from collecting.
Root rot can be seen in the shrivelling of the lower leaves and is mainly caused by over-watering. Re-pot in a new medium and ensure good drainage. Remove all damaged roots and keep the good ones dry and then treat with a weak chlorine solution before re-potting them. Remember not to water for several days.
Another bacterial infection can cause wet brown spots on leaves and pseudobulbs. The disease is serious and all the affected areas need to be pruned and treated with chemicals like Thiram or other anti-bacterial agents.
Well I hope you will consider planting orchids in your garden. Send me an email for further details. Happy gardening.