This is part three of a series on growing orchids as houseplants. My hope is that once you understand these unusual plants, you will take the plunge and start raising them. You do not need a greenhouse for many of the easier orchids. You simply need to be willing to manipulate the humidity and temperature in your home environment.
Let’s start with humidity. I will not kid you- orchids must have high humidity, definitely higher than the average home, which dips to 20% or less in the winter months. The goal is to provide a minimum of 40-50% humidity for easy care orchids during the day when the plants are receiving light. Misting your plants may seem like the most obvious way to provide this moist air. Although misting is good (as long as it is not done in the evening when the foliage will go into the night with wet leaves), it is a temporary and labor-intensive solution. I prefer to grow orchids on humidity trays. The simplest version is to place the plant on a saucer that is 4” greater in diameter than the pot the orchid is growing in. Fill the saucer with pebbles, set the plant on top of the pebbles, and add water until it comes to just below the top of the stones. NEVER let an orchid plant sit in water. As the water evaporates from this pebble tray, it surrounds the immediate area of the orchid with 40-50% humidity. You can group orchids with similar needs together on windowsill trays made of copper or other rustproof metal, glazed ceramic, or plastic. You may also be able to find decorative waterproof plant stands that will hold a grouping of orchids. In the morning, refresh the water, as much will have evaporated during the night, especially if it is wintertime and the heat is on. Another approach to raising the humidity around orchids is to grow them in freestanding ornamental glass cases. These were originally found in old fashioned parlors and are coming back into fashion again. The glass cases should have doors that open so that the humidity level can be controlled and the case can be vented if it gets too warm or too wet.
Temperature is a critical factor in raising orchids. There is no general rule that applies to all orchids- different orchids require different temperatures. Rather than trying to retrofit your home to accommodate a plant you admire, determine the temperature range that you normally keep your home at and pick plants to fit your conditions. The basic rule of thumb is that orchids need at least a 5-10 degree drop in temperature in nighttime versus daytime temperature. Phalaenopsis or moth orchids are probably the most common orchids sold to homeowners today. The reason for this is that they prefer warm conditions, with nights kept at about 65 degrees and days reaching 70 degrees or more. This is pretty typical of average home conditions in a sunny or partially sunny plant room. A second category of orchids should be grown at intermediate temperatures, with nighttime temperatures kept at a range of 55-62 degrees and daytime temperatures rising 5-10 degrees to 65-75 degrees. They should never be allowed to grow in extremely hot conditions above 85 degrees. Sunny rooms should be vented during the day, especially as the intensity of the sun increases in late spring. In the summer, this category of orchids does best outdoors, sitting beneath or hung from a tree in dappled sunlight. Realizing that 55-62 degrees is cooler than the average home at night, you should only grow orchids in the category if you have a cool spare room or a heated sun porch where you can drop the temperature at night. Orchids that thrive in intermediate temperatures and that can be grown in the home environment include Dendrobiums, Cattleyas, and tropical lady slipper orchids (Paphiopedilum) with mottled leaves. A third category of orchids are those that grow in a cool environment, with night time temperatures in the winter dropping to 45 to 50 degrees and daytime temperatures of 50-60 degrees. This is a specialized environment that not all homes can provide. If you have a very cool spare room or enclosed porch where you can control the temperature both by minimal heating and by ventilating during the day, you can grow Cymbidium orchids as well as Paphiopedilum with solid green leaves. If you have ever been given a gorgeous Cymbidium orchid as a gift that was in full bloom and you are wondering why you have never been able to get it to bloom again, think temperature. Without a definite drop in nighttime temperatures, it simply will not produce new flower buds. One trick I have found is to locate my Cymbidium orchids on the floor of my plant room. As hot air rises, and the room is not extremely well insulated, the floor is much cooler. In this way, I can grow both intermediate and cool orchids in the same space.
This article was originally published in the Shore Publishing newspaper as a part of Nancy DuBrule-Clemente’s column “In the Garden”.
In an effort to provide horticultural information, these educational documents are written by Nancy DuBrule-Clemente and are the property of Natureworks Horticultural Services, LLC. You are granted permission to print/photocopy this educational information free of charge as long as you clearly show that these are Natureworks documents.