Dendrobium Orchids

Dendrobiums are among the most commonly encountered orchids in the retail trade.  Like most other cultivated orchids, dendrobiums are epiphytes, or air plants.  They have well developed water storage organs (pseudobulbs), often called “canes” for their upright, leafy appearance.  They should be potted in porous, free draining media. There are many different types of dendrobiums available to the specialist grower.  However, hybrids involving Dendrobium phalaenopsis are what you will most often encounter.




Sufficient light is important for healthy growth and flower production.  Provide bright light, to 50 percent sun.  In the home, an east, west or lightly shaded south window.  In a greenhouse, about 30 to 50 percent of full sun.  Under lights, four 40 watt fluorescent tubes and two 40 watt incandescent bulbs directly over plants.  Plants should be naturally erect, without need of (much) staking, and of a medium olive-green color.




Mature plants need a 15 to 20 degree F difference between night and day.  Provide nights of 60 to 65 F, days of 80 to 90 F.  Temperatures up to 95 to 100 F are beneficial if humidity and air circulation are increased.  Low temperatures (below 50 F) may cause leaf drop.




Keep evenly moist while in active growth.  Allow to dry between waterings after growth is mature (indicated by terminal leaf).




Dendrobiums need 50 to 60 percent.  In the home, place on trays over moistened pebbles.  In greenhouse, use a humidifier if conditions are to dry.




Should be provided on a regular basis during the active growing period.  The exact fertilizer you use will depend on the mix in which your plant is growing.  A good general rule is to apply a balanced 20-20-20 fertilizer (or orchid fertilizer) during the period of active growth.  That is, fertilize every week at one quarter to one half of the recommended dilution.




Should be done every two to three years before mix loses consistency (breaks down).  Pot firmly in medium, giving aeration and ample drainage, allowing enough room for two years’ growth.  Dendrobiums grow best in small pots for the size of the plant.


Orchids in the Home


Anyone can grow orchids in the home without living in the tropics or having the luxury of a greenhouse.  Today, houseplants are a regular part of home decoration.  If you have ever successfully grown a houseplant, or enjoyed a flowering potted plant, you can grow orchids.  The good news is there are plenty of options to give you a beautiful display of flowering orchids year round.  Hint:  Orchids grown in the home during the colder months will respond wonderfully well to being summered outdoors in a protected area.  This will also extend the range of plant selections available to you.  Be sure to read the AOS’s companion sheet Orchids in the Garden and on the Patio.




No flowering plant will do well without sufficient light.  In the home, where most available light is incidental (that is, at an angle, and therefore less intense), plants will need to be fairly close to an east or west, or lightly shaded south window.  A north window will rarely provide adequate light.  If light is too intense in a southern exposure, a sheer curtain could be hung to diffuse the light.  Extra hours of light will not entirely compensate for poor light quality.  Indeed, extending day length artificially to more than 16 hours can be detrimental to the plant’s health and often will prevent flowering.




The plants will be comfortable where you are comfortable.  Typical home temperatures of 55 to 60 degrees F at night and 75 degrees F during the day are fine.  Guard against excessively low or high temperatures immediately adjacent to glass windows.  Some leeway for seasonal fluctuations is allowed.




Rugs, drapes and some furniture act as giant wicks that absorb the home’s humidity, as do heating and air conditioning systems.  Also, it is not advisable to have the home’s interior be too wet to accommodate the plants.  Solutions:  Group plants to take advantage of their collective transpiration (exhaled moisture) or place them on gravel-filled humidity trays to raise the humidity to 50 percent.




Care must be taken to balance the rapid surface drying that can take place in the home with the plant’s lower metabolic processes resulting from lower light.  Each particular type of orchid will retain its basic water needs, whether for moisture or periodic dryness.  The home grower also needs to give thought to the logistics of watering.  You can carry plants to the sink or even outdoors (when weather allows), or water them in place and remove excessive water so the containers do not sit in water.




Fertilize regularly at a low dosage of approximately one-quarter strength with a fertilizer appropriate to the potting mix in which your plants are grown.  Fertilize less often during the winter.


Selection of Plants




Dwarf Madagascaran species, fragrant at night; bright light.


Cattleya Alliance Hybrids and Species


Choose miniature types less than 10” tall; bright light of southern exposure is best.




Dwarf phalaenopsis types, or higher-altitude miniatures; bright light at south window required.




Many types available in flower, best if smaller growing; bright light.




Lady’s slipper orchids grow well under home conditions, giving long lasting blooms; provide African-violet conditions.




Moth orchids are absolutely the number one best orchid houseplant; provide African violet conditions.