Orchid Care: Dendrobium
Dendrobium is a spectacular genus which contains the greatest diversity of horticulturally interesting specimens. They are native from Asian and South Pacific tropics and subtropics, to lowland warm regions to Himalayan mountains, guaranteeing a wide range of cultural requirements. Most dendrobiums are epiphytes, growing in the branches of trees, getting food from air, water and decaying matter that their root systems trap.
GENERAL NOTE Because of so many different species, culture can be confusing. Some are deciduous while others are evergreen. Both types may need a dormant period, usually for several months in winter. Other types grow actively all year round. Obviously, the trick is to figure out what type you are growing.
POTTING Dendrobiums must be properly potted, with close attention to type of medium (fine to medium textured, excellent drainage — fir bark is excellent) and pot size (small compared to plant size). They will benefit from being pot-bound and, in general, do not like being disturbed. Soak your medium overnight before potting.
TEMPERATURE During the summer the cool-growing varieties require a minimum night temperature of 55°F with a daytime rise of up to 85°F. The warmer growing types should be kept nearer to 65°F at night, again with a considerable rise during the day, which can exceed a cool house temperature for a few hours during the hottest part of the day. During the late autumn months, the plants should be moved to their winter quarters. For the cool-growing types, a winter night temperature of 50°F will suit them well, with a daytime rise to at least 65°F. The warmer growing varieties will require a night time temperature of 60°F with a correspondingly higher daytime temperature.
LIGHT Most dendrobiums need bright light. If the right type of cultural regimen is being followed for whatever dendrobium is being grown, and still no flowers appear, low light is probably the cause.
WATER In the spring, when dendrobiums start their new growth after having remained dry during the winter months, it is advisable to flood the surface of the growing medium two or three times to ensure that the moisture penetrates throughout the pot. During the summer months the aim should be to keep the medium continually moist, to ensure a continuous steady rate of growth. In addition, they may be lightly sprayed with water several times a day during bright, sunny spells. Where the plants are being grown indoors, making spraying difficult, they will benefit from having their leaves sponged off just as frequently. Beauty requires effort!
FERTILIZING A diluted 20-20-20 fertilizer is recommended only when in active growth, at every third or fourth watering. Or use 30-10-10 twice a month if planted in fir bark. Fertilizer solution can be applied to the pot or as a foliar feed spayed over the entire plant.