For variety of color, floriferousness and long lasting flowers, few genera of orchids can surpass these lovers of cool temperatures. Cymbidiums are divided into several types. The Standard Cymbidium is differentiated from the Miniature Cymbidium principally by the size of the flower and the fact that the Standard Cymbidium wants a slightly cooler night temperature in the fall and Winter.
Temperature – In the spring cymbidiums love to be moved out of doors as soon as the night temperature is going to stay in the mid 40’s or above and not come back in until a light frost, very light, in the fall. It is very helpful, if practical, to bring the cymbidiums in when frost is likely and then put them back out if it warms up. Very important for initiation of spikes is good temperature differential from night to day. This can be achieved in the summer by sprinkling the leaves in the late afternoon or early evening for evaporative cooling. If the night temperatures are too high the spikes, will not develop. Most Miniature Cymbidiums do best throughout the winter with a maximum night temperature of 55°F. While Standard Cymbidiums want a maximum night temperature of 50°F.
Humidity and Ventilation – Humidity is less critical with Cymbidiums than with most orchids but this does not mean you can ignore it completely. Of course since they grow outside so much of the year, there is not much you can do anyway. Air movement is essential at all times, in Summer for cooling and in winter to avoid stagnant air and fungus problems.
Light – From spring to autumn cymbidiums should be grown in the maximum amount of light (but not full sun) that is consistent with keeping the foliage cool (it will sunburn). The amount of light you can give your plants may be in direct relation to the availability of someone to mist the foliage on hot summer days, if this is impractical then you must balance the light levels with daytime temperature. Remember, when you first move them outside, that they are not yet use to strong sun, acclimate them gradually. As plants come into bud shading is gradually increased.
Watering and Feeding – The word wet exists in our orchid vocabulary only in dealing with cymbidiums. Cymbidiums should never be allowed to become dry (but like good drainage and ventilation). To this end we prefer plastic pots and nursery containers to facilitate the maintenance of adequate moisture for the plants. Sprinkle Cymbidiums thoroughly in the very late afternoon on every hot summer day, to reduce the temperature by evaporation. Cymbidiums need to be fed every two weeks with a balanced fertilizer (such as Peters 20-20-20) from March until September to help establish good vigorous growth, and in turn to increase the likelihood of a good number of spikes in the fall. As for late winter and the fall, the plants should be fertilized once every three weeks and once a month in the mid winter.
Pests – Aphids and mites are probably the worst insect pests bothering cymbidiums. Malathion or X-clude are effective against these insects, Kelthane is especially effective against mites. Remember that these products are intended to kill and should be used in the open air outside your home with caution. A light horticultural oil, like Year Round, (not a dormant oil) which smothers insects and their eggs is quite effective against most pests and fairly safe. Insecticidal soap is also effective and reasonably safe, but it has no residual action. Plain soap and water is also effective, most insects can be controlled by washing plants thoroughly. The most effective control is early control. One or two insects can be cleaned up easily, a few generations later and it’s a much bigger problem. Slugs and snails find cymbidiums attractive too, products containing Metaldehyde such as Deadline and Slug Baits can help control these pests. Diatomaceous Earth is quite effective against slugs and Beer in a shallow bowl is a good trap for them. With any of these products some insects, and especially their eggs will survive to breed again. One dose of even a systemic insecticide will not wipe out a large population of insects totally and completely. Remember to use any of these products with caution and in accordance with the manufacturers label.