Two weeks ago Lee and I celebrated five years of being together. To commemorate the day, Lee bought me a beautiful orchid from the farmer's market. The flowers on the orchid are bright magenta and intensely suggestive, with layers of petals surrounding the sexual parts. I find the flowers mesmerizing and the orchid itself amazing in its ability to produce a flowering stalk that dwarfs the rest of the plant. I hope to keep our orchid alive for many years to come, so I researched orchid types and care.
Our orchid is a moth orchid in the genus Phalaenopsis. Moth orchids are native to the lowland rain forests of India, southeastern Asia, Indonesia, and northern Australia. Phalaenopsis orchids have become popular as houseplants because they are easy to care for, relative to other orchids, and they bloom for months at a time, sometimes multiple times a year. The showy flowers on Phalaenopsis orchids range in color, from whites to pinks to purples, and in pattern, from solid to faded to spotted. In its native rain forest, the scent and display of the flower would attract a specific fly, who would try to mate with the flower and, in the process, get covered in pollen to be carried to the next flower visited.
Phalaenopsis orchids are epiphytic, which means that they live on the branches of rain-forest trees. Epiphytic orchids have long, cord-like roots that can be seen climbing out of their pots. In the rain forest, the long roots securely attach the orchid to a tree branch and capture rainwater for the plant. Epiphytic orchids, like other plants, are able to use sunlight to make sugar, their food source, but they also need nutrients, including nitrogen and phosphorous, that plants normally absorb from the soil. Orchids have adapted to living with low levels of nutrients, which they absorb from fallen leaves, bird droppings, or other organic matter that accumulates in tree branches.
The goal of caring for a Phalaenopsis orchid as a houseplant is to mimic the natural conditions of the lowland rain forests:
Water Phalaenopsis orchids frequently enough to keep the roots moist but not wet. Watering about once a week is a common suggestion, with more frequent watering in the summer or during active blooming and less frequent watering in the winter. It is preferable to water orchids in the morning, because evening watering can promote fungal diseases. Water with room-temperature (not cold) rainwater, spring water, or filtered tap water. Between waterings, the roots should dry enough that the plant becomes significantly lighter, but the roots should never be allowed to dry out completely, as orchids do not easily recover from becoming wilted. It is equally important that orchid roots never sit in water, because their roots are adapted to being in the open air, not in the soil, and will rot if they become waterlogged.
Phalaenopsis orchids are considered warm-temperature orchids because they normally grow at or near sea level in the tropics. Their ideal temperature range is 70 to 85 degrees F during the day and 65 to 70 degrees F at night. They grow best when the night temperature is about ten degrees cooler than the daytime temperature, allowing the plant to metabolize more slowly in the evening. A drop in the night temperature, which usually happens in the fall, induces flowering in the moth orchids.
Phalaenopsis orchids need low light levels. North- or east-facing windows, or shaded south- or west-facing windows, are good places for Phalaenopsis orchids to live. Moth orchids require six to ten hours a day of light with an intensity of 1200 to 2000 foot candles. I have to admit that "2000 foot candles" is totally meaningless to me. More tangible definitions of low light range from having enough light to be able to read a book to having enough light to cast a fuzzy, but not clear, shadow on the leaf of the plant when a hand is held over a leaf. Phalaenopsis orchids that do not receive enough light will have dark green leaves, as opposed to brighter green leaves on orchids in sufficient light, and will not be able to produce a flowering shoot.
Moth orchids need moderate levels of humidity. Higher levels of humidity in the summer, when the temperatures are higher, are fine for orchids because the higher temperatures speed evaporation. High humidity at low temperatures can promote fungal growth on the plants, due to low evaporation rates, and extremely low humidity can be damaging to the plants at any temperature. The recommended solution for low humidity, which is often caused by central heating, is to place a tray of water under the orchid plant during the winter months to increase the humidity around the plant. When using a humidity tray, make sure that the orchid is not sitting directly in the water, or its roots will rot. Because orchids are prone to fungal diseases, it is also important that there is air circulation around the plant.
Finally, orchids require less fertilizer than most potted plants because they are adapted to low-nutrient conditions. Some Phalaenopsis orchid growers follow a "weekly weakly" fertilization plan, meaning that they fertilize their orchids with very dilute fertilizer once a week. Other growers recommend fertilizing once a month with an orchid-specific fertilizer. Fertilize after watering because the roots are more able to absorb nutrients after they have expanded with a recent watering. If watering with distilled or highly-filtered water, it is important that the orchid receives a fertilizer that contains all the micronutrients (iron, manganese, zinc, copper, boron, molybdenum, chlorine) normally found in spring water as well as the macronutrients (nitrogen, phosphorous, potassium, calcium, sulfur, and magnesium) normally found in fertilizers.