Phalaenopsis, also known as the “moth orchid,” is perhaps the best orchid for growing in the home, and is also a favorite with greenhouse growers and customers. Though the main season for flowering is late winter into spring, healthy plants flower often – sometimes with a few flowers throughout the year. Average home temperatures and conditions are usually sufficient to maintain healthy orchids. Flower stems on certain hybrids can be forced to re-bloom by cutting the tip off after the initial flowering. Only healthy plants should be induced to flower repeatedly.
LIGHT is easy to provide for phalaenopsis. They grow easily in a bright window, with little or no sunlight. An east window is ideal in the home; shaded south or west windows are also acceptable. In overcast or northern winter climates, a full southern exposure may be needed. Artificial lighting can be created easily and will suffice. Four fluorescent tubes in one fixture, supplemented by incandescent bulbs, are placed 6 to 12 inches above the leaves for 12 to 16 hours a day, following the natural length of the day. In a greenhouse situation, shade must be given; 70 to 85 percent shade, or between 1,000 and 1,500 foot-candles, is recommended. No shadow should be seen if you hold your hand 1 foot above the plant's leaves.
TEMPERATURES for phalaenopsis orchids should usually be kept above 60°F at night, and range between 75° and 85°F or more during the day. Although higher temperatures force faster vegetative growth, higher humidity and air movement must accompany higher temperatures, the recommended maximum being 90° to 95°F. Night temperatures up to 55°F are desirable for several weeks in the autumn to initiate flower spikes. Fluctuating temperatures can cause bud drop on plants with buds ready to open.
WATER is especially critical for phalaenopsis. Because they have no major water-storage organs other than their leaves, they must never be allowed to completely dry out. Plants should be thoroughly watered and not watered again until nearly dry. In the heat of the summer in a dry climate, this may be every other day; in the winter inside a cool northern greenhouse, it may be every 10 days. Water only in the morning, so that the leaves dry by nightfall, to prevent rot.
HUMIDITY is important to phalaenopsis, the recommended humidity level being between 50 and 80 percent. In humid climates, such as in greenhouses, it is imperative that the humid air is moving. Leaves should be dry as soon as possible and always by nightfall. In the home, set the plants on trays of gravel that are partially filled with water, so that the pots themselves never sit in water.
FERTILIZE regularly, especially if the weather is warm, when the plants are most often growing. Twice a month, apply high-nitrogen fertilizer (such as 30-10-10) if bark-based media is being used. Otherwise, a balanced fertilizer is best. When flowering is desired, a high-phosphorus fertilizer (such as 10-30-20) can be applied to promote blooming. Some growers apply fertilizer at one-quarter strength with every watering; this is best for warm, humid conditions. When cooler or under overcast conditions, fertilizer should be applied twice per month at weak strength.
POTTING is best done in the spring, immediately after flowering. Phalaenopsis plants must be potted in a porous mix. Potting is usually done every one to three years. Mature plants can grow in the same container until the potting medium starts to decompose, usually in two years. Root rot occurs if plants are left in a soggy medium. Seedlings usually grow fast enough to need re-potting yearly, and should be re-potted in a fine-grade medium. Mature plants are potted in a medium-grade mix. To re-pot, remove the old medium from the roots, trim any soft or rotted roots, and spread the remaining roots over a handful of new medium in the bottom of a new pot. Fill the rest of the pot with medium, working it among the roots, so that the junction of the roots and the stem is at the top of the medium.
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