The Dendrobiums belong to a very diverse genus, consisting of numerous evergreen, semi-deciduous, and deciduous species. This culture sheet deals with only three of the many genus.
PHALAENOPSIS OR ANTELOPE TYPE. Tall, thin canes, flowering on sprays from the tops.
NIGRO-HIRSUTE TYPE. Fine dark hairs on canes, flowers direct from canes.
Temperature - Dendrobiums can withstand hot weather if adequate ventilation and humidity are provided. They do best when the temperature is between 65°F and 75°F in the day and between 55°F. to 60°F. at night.
Humidity and Ventilation - A minimum humidity of 50% is generally considered a necessity. However it does not need to be constant, in the home, morning misting and or gravel trays (Remember not to sit the pot directly on the gravel) are usually enough. Air movement essential at all times, but especially critical when the humidity is very high. In the home, natural air movement is usually enough, but in enclosures and greenhouses, fans are recommended.
Light - They need an abundance of light, but not direct sun. A lightly shaded South window is best. East or West facing windows are satisfactory if bright (avoid direct sun except at the beginning or end of the day).
Watering and Feeding - Always water orchids in the morning so that the leaves are dry before night. How often to water depends on the potting media used, the type of pot (plastic or clay), and the size of the pot. Dendrobiums do not like to be potted in large pots, and are often as much as ten times as tall as the pot is wide. Because they are usually large plants in relatively small pots, watering twice a week is about average. They like to be watered well, drained well and like to be almost dry before re-watering. Feed plants potted in bark with Peters 30-10-10 twice a month in the Summer, every three weeks - Spring & Fall, and once a month in the Winter.
Pests - Slugs and snails can be controlled with products containing Metaldehyde such as Deadline or Slug baits. Diatomaceous Earth is quite effective against slugs and Beer in a shallow bowl is a good trap for them. For mealy bugs, scales and other pests use insecticides like Malathion or X-clude. Remember that these products are intended to kill and should be used in the open air outside your home. A light horticultural oil, like Year Round, (not a dormant oil) which smothers bugs and their eggs is quite effective against most pests and fairly safe. Insecticidal Soap is also effective against these insects and reasonably safe, but it has less residual action. 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. In the home, vigilance is often the best defense against pests. If you get them early, before they start laying eggs, they can be eliminated relatively easily. Remember to use any of these products with caution and in accordance with the manufacturers label.