Orchids for Terraria
I get questions all the time about orchids that are well-suited to different forms of indoor culture- under lights, orchidaria, terraria, that sort of thing. This following is meant as a primer for those that enjoy
terrariums and their contents (frogs, snakes, lizards, that sort of thing) but know relatively little about orchids.
The majority of plants that are sold for terrarium culture come from tropical forest floors- philodendrons and other species that grow in a very humid, dark climate. They require relatively little light, and things
like air movement and drying cycles are unknown. For many orchids, this is certain death, for reasons that will be discussed shortly.
The majority of orchids- about 75% of all species- are epiphytes. This is to say, they live on other plants, usually trees, some distance off the ground. This environment is very different from that on the forest
floor: there is more light; there is air movement- usually constant; and there is a sharp wet-dry cycle from light rain or condensation that falls, often daily.
These factors are very important, as sub-optimal conditions will increase stress in the plant, and often cause rot or death. At the very least, unhappy plants won’t flower, and may steadily diminish in size
until they whither away.
Most terraria are kept at very high humidity; orchids do not find this objectionable, and most do best with humidity at 60% or higher. Some enjoy it at levels considerably higher than this. However, high humidity has
a drawback in that it does not allow condensation or other water on the plants to evaporate quickly; as a result, plants may rot. The chances of rot at very high humidity may be reduced by using a small fan
(“muffin” fans, such as those used to cool computers and other electronics), powered by a small transformer such as those used to eliminate batteries. A variable voltage battery eliminator in conjunction
with a fan allows one to control the amount of air being moved. These components may be found on the Internet, or from local electronics stores. Look for small, 12-volt DC fans. These fans can be put into the top
corner of a terrarium to recirculate air throughout the chamber. A small amount of mesh may be placed on either side of the blades to prevent injury to animals that might get that far up.
Above all, leaves should be dry by the time the lights go out. Moisture on the leaves after dark directly encourages fungal growth that may eventually destroy your plants. A sharp wet-dry cycle is appreciated by many
orchids; mist them until moisture drips off the roots or runs out of the pot, and allow to dry before watering again. Watering is best done in the early morning. If this is not possible, make sure watering is
performed long enough before dark that no water remains in the crown of the plant. While most orchids enjoy wet-dry cycles, some orchids prefer a little moisture around the roots at all times. These orchids are in
the minority, and if the wrong amount of moisture is provided, either the roots will rot, or the leaves will shrivel. A little research from the seller or on the web will provide cultural information for most plants.
Water quality is important. If your tap water has a lot of dissolved salts, reverse osmosis or distilled water should be used. Fertilizer should be applied weakly (1/2 label strength or less) on a regular basis. Many
people use “SUPERthrive” or similar growth-enhancing additives, which are very good at stimulating root growth and enhancing color and quality of foliage. Direct application of nutrient solutions to the
roots- avoiding the leaves- may prove beneficial, particularly if the plants in culture are particularly prone to rot.
Lighting is another subject entirely, one which requires a lot of specialized knowledge. The amount of light that orchids require may prove to be more than many terrarium animals enjoy; however, there are some
orchids that can be grown under relatively low light, such as “jewel” orchids (Haemaria discolor, many Goodyera species). It is also possible to place orchids higher in the terrarium, closer to the
lights, which affords shade for the plants and animals below. This may provide a better utilization of space and light. I’ll leave selection of the light source (incandescent, fluorescent, VHO, etc.) to other,
better writers. Insufficient light intensity is one of the leading reasons as to why your orchids may not be flowering.
What you grow your orchids on is also important. As they are epiphytes, they enjoy plenty of air circulation around the roots- otherwise, they might rot. One of the best way to grow orchids is on a
“plaque,” such as a slab of cork, a piece of bark, a cedar shingle, or even a piece of plastic foam that has been “painted” with a couple of layers of concrete. If not purchased on a plaque,
orchids may be secured to a slab with monofilament fishing wire, or dental floss (or dental “tape”). Smaller plants should have a bit of sphagnum moss around the roots as well so that a bit more moisture
is retained at the roots when watered. Otherwise, plants may dry out too quickly; roots that dry out quickly will not grow, and plants will slowly go into collapse- leaves shrivel, and the plants are less prone to
produce more roots. A downward spiral continues until interrupted, or the plant dies.
Temperatures are relatively unimportant for most tropical epiphytes that are commercially available. Orchids are generally broken into cool, intermediate, and warm growers. Stick with intermediate and warm species,
unless you have the ability to keep plants at or below 55 degrees F at night, and under 80 or 90 degrees F during the day. Cool-growing species may do well in terraria at these temperatures, but might not flower.
Other growers report few problems at even higher temperatures- it depends upon the aptitude of the grower, and the species in question.
This is not meant as an all-inclusive monograph on the subject; in general, pleurothallids and allied genera will do quite well in terraria, both as terrestrial and epiphytic species, depending upon the individual
species. Other orchids- including oncidiums, ornithicephalus, and other small, “charming” species, do quite well as epiphytes. Some of the smaller phalaenopsis species thrive under the lighting and
humidity in terraria. If in doubt, check with growers to see what they have that might meet your conditions. Maybe you’ll come away pleasantly surprised.