Orchids can be grown very well in Colorado, but the extremes of our climate require considerable modification to grow the tropical cultivated type, whether in a greenhouse or in the home. The sunny climate offers many more bright days than many parts of the United States, as well as ample opportunity to damage plants through excessive light. And while the low humidity can severely desiccate a plant in a matter of days, it allows effective temperature control through evaporative cooling.
It definitely takes a little more effort to grow orchids well here than in some areas, but the results are particularly gratifying during the long winter while outdoor plants are dormant.
Light
A south or east window is ideal for most types, with a sheer curtain used as needed. Fluorescent lights work well; also, leaf tips should be kept 3 to 6 inches from the tubes. The greenhouse grower will want to reduce the available light by 50% or more using lath covering, shade cloth, or latex shade material. The leaves of most plants should be a medium green color. Yellow-green leaves generally indicate excessive light. Leaves that are very dark green, thin and brittle, often result from inadequate light.
Water
Orchids must be grown in a porous mix, so through wetting of the roots is crucial and sometimes difficult for the home grower. Water must be applied generously, and any excess removed so plants do not stand in water. An occasional soaking in a bowl or sink is helpful. Some types should become almost dry before watering again; others should remain damp. Check below the surface to be sure. This might require several days to a week, depending on conditions. IN the greenhouse, proper watering is much simpler. Water should be applied until it runs out of the bottom of the pot. Excess minerals can be flushed away by watering again later the same day before the plants have dried. This helps to maintain an active and healthy root system, and should be done occasionally, if not at every watering.
Local water supplies vary in quality. Most are hard, but adequate; a few have too much sodium for orchids. Water from home water softeners also contains sodium, and should not be used on orchids.
Humidity
This is probably the hardest need to satisfy in the Colorado climate. In the home, pebble trays, other plants, misting, and cool mist humidifiers will help. Any inexpensive humidity meter will serve as reassurance or warning that conditions must be improved. It is important to remember that extra water in the pot cannot compensate for low humidity; it will only rot the roots.
40% to 60% is suggested. In the greenhouse, a variety of swamp coolers, cooling pads, mist nozzles, and other devices may be employed to provide humidity as well as summer cooling.
Temperature
Orchids will appreciate recommended lower house temperatures almost as much as our checkbooks do. Even those considered warm growing need only 60 to 65 degrees, They suffer as we do on the hot days of summer, but will survive if proper humidity is maintained. Be careful of temperature extremes from strong direct sun or contact with freezing windows. Temperature control in the greenhouse is equally crucial summer and winter. The sun can rapidly raise the enclosed air to 50 degrees or more above outside temperatures. Circulating fans, as well as thermostat controlled exhaust fans, are a clear necessity.
In winter, double wall insulation with plastic sheeting is a virtual necessity from a conservation and economy viewpoint, as well as to prevent freezing of leaves near the glass. The temperature to be maintained will depend on the types of plants grown, with about 50 degrees being about the minimum allowable to maintain most kinds in reasonable health. While Phalanopsis initiate bloom at these conditions, they will generally grow and bloom better at higher temperatures as will many other warm growers.
Feeding
Most orchid mixes supply very little nutrient to the plants, so fertilizers are necessary. Orchids are not heavy feeders and their roots burn easily. Use a dilute solution (about ¼ tsp per gallon) of a balanced fertilizer, preferably one made for orchids, about twice a month. The analysis of the major nutrients is important for best results. A high nitrogen fertilizer (30-10-10) may be used for seedlings and many plants in rapid-growing seasons, but might inhibit flowering if used constantly on mature plants. A lower nitrogen formula (10-30-20 or 20-20-20) applied as the season’s growth matures will help to promote proper flowering.
