Dendrobium (den-DROH-bee-um) is a diverse genus and is the second largest genus with over 1200 species. They range throughout the Pacific, including Australia, and in Asia from India east through China. They are one of the most commonly encountered orchids offered for sale today and are well worth the time to grow since their flowers will last from weeks to months at a time.
In general, they have a cane-like pseudobulb that looks something like a bamboo cane with leaves growing along the canes. The inflorescences will develop from the top of the plant either on new growth or re-bloom from the previous year’s growth. The stem will grow up initially until the weight of the stem and buds cause it to arch down. They can be allowed to arch naturally or be staked to hold the flowers upright. I like to allow them to develop naturally and place the plant on an upturned pot so that they are displayed well.
The most commonly seen Dendrobiums are those from the Phalaenanthe group. The name comes from the shape of the flower which looks much like a Phalaenopsis. They generally bloom in the winter or spring and often will bloom twice a year. The blossoms come in a variety of colors from white to dark purple. There are even some with striped flowers.
There are two main size groupings of Dendrobiums seen—standard (approximately 2-3 feet) and the miniatures (1 foot) tall. The large types are grown for their long-lasting flowers mainly for the cut flower trade. There is no reason that the hobbyist cannot grow them, but they do take up a lot of room. The miniatures with their smaller flowers and size are much more suited to the home grower.
Many of the Dendrobiums go through a growth period and then a rest period based on time of year and temperature but hybrids based on Den. Phalaenopsis grow year round. They should be potted in well draining medium and need medium light and heavy fertilizer while in a growth period. They are warm to intermediate growers (60 degrees at night, and 85 degrees to 90 degrees during the day) and will do well grown in the same conditions as Phalaenopsis including the cooler month of 50-55 degree weather in the fall to promote blooming. During this rest period, cut back on watering until new growth is seen. If it is too cool or dry, the canes will loose all their leaves. Don’t throw them away, increase heat and watering in the spring and they should put out new growth.
Most of these orchids grow best rather pot-bound—in other words in pots that look too small for the plant. This encourages growth and flowering. If you are growing the standard types (2-3 feet), be sure that you put regular rocks or black lava rock in the pot before you put in the potting medium. This adds necessary weight to hold the plant upright and keep it from tipping over. I also use stakes to hold the plants upright and keep them straight.