Compiled by Dixie McCulloch, a longtime KOS member who joined in 1988.
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Winter can be the most difficult season for your orchids. During the winter the days are shorter, when watering, soak plants thoroughly and do so only in the mornings, making sure your plants are dry before nightfall. The lower the temperature the less you should water. However, artificial heat often causes serious drop in humidity and overly dry conditions in your growing area. Be sure to watch your plants closely to insure that they do not get too dry. Space heaters and home furnaces create their own set of problems. They will be running more thus drying out the air. Dry air can cause bud blast. Always remove old flowers or dead leaves, as they can be carriers for insects or fungus.
This time of year plants may be fed a balanced fertilizer such as 20-20-20 at half strength every other week. An occasional application of a fertilizer with a higher middle number for bloom initiation can also he used for the spring blooming plants.
You should keep a close eye out for orchid pests in the greenhouse. One of the main ones this time of the year is aphids. They can start up and cause considerable damage to your plants if not controlled right away. Some good controls I use are: Malathion—WP l tsp/gal; Diazinon—WP 1 tsp/gal; Orthene—WP (only) 1 tsp/gal; plus several others that can be used. The only thing to remember is to alternate the sprays so the aphids will not build up an immunity to them. Slugs and snails are another problem during this time of the year. The two baits that I use are QUE Slug and Snail granules, that I just sprinkle on the pots, or Slug-Spray 50 WP—1 tbs/gal, that I spray on everything in the greenhouse every two weeks until the slugs and snails are gone. (Written by Ronald A. Sellon.)
Cattleya and Laelia: The temperature should be moderate with minimum 60–65 in the day and 54–59 at night. The potting mix should not be allowed to get completely dry. Keep plants that have new growth showing a little more moist. Watering and feeding needs are at a minimum, over watering and over fertilizing can cause rot and soft growth.
Cattleyas that have completed their flowering should be kept on the dry side until their normal growing period begins in spring. Go over each plant and remove the dried skin on the pseudobulbs, which is a favorite haven for scale, but be careful that you do not injure the eye at the base of the pseudobulb.
Cymbidium: Keep them moderately moist but not wet. Plants in bud should be given more water and fertilizer. Later varieties are just beginning to push up their flowering stems; watering frequency and volume is important to support the development of the inflorescence. Cool temperatures are beneficial.
The early flowering varieties, which end their flowering this month, should be allowed to rest. They need less water. A daily misting of the pseudobulbs and foliage to prevent dehydration is enough.
Lycaste: Watering tapers off now as the spikes start growing. Start staking soon to better position the flower spikes so as not to interfere with each other. Bright filtered light will increase stem strength. Do not readjust to a different direction than they are growing, as this ultimately will cause twisted stems.
Paphiopedilum: Reduce water only slightly. The temperature should be as given above for intermediate house. Plants developing buds should be kept a little warmer.
Standard hybrids are in about the middle of their blooming season, so enjoyment is the key word. They still require watering and light feeding, especially if they are in the drier home environment. More light will help to set buds for the spring and summer bloom season.
If any early flowering varieties have finished blooming and the potting material is in poor condition or the plant overcrowded, repot. If you are growing on a windowsill, use a pebble tray with water in the pebbles, to increase humidity. Keep water out of the sensitive pouches; accumulated moisture shortens flower life. Watch for insects on the foliage, particularly red spider mites.
Phalaenopsis: Warm house temperatures are required, with higher humidity. Phalaenopsis have no resting period. Be careful that the potting mix does not dry out. Bud development requires more light in order to prevent yellowing.
Constant air circulation is essential to avoid the heartache of Botrytis-spotted blooms. Water carefully to keep flowers dry and to minimize risks of soft rot in the fleshy leaves. Fertilize sparingly with a liquid or granular formula, and only when the medium is moist. Begin careful monitoring for scale and mealy bug on the inflorescence and under sides of leaves.
Stake the spikes so the flowers will be shown to their best advantage.
Dendrobium: Burmese and nobile types require a strict resting period, according to most growers. There is much to be learned about these orchids but it is generally felt they need high light, very little water, and humidity as low as possible at this time of year. Continue the water sparingly, or not at all, those species that require a dormant period before flowering this spring (Den. aggregatum, Den. chrysotoxum, Den. farmeri, Den densiflorum and Den. nobile or its hybrids). As the buds begin to emerge, gradually increase the watering frequency and amount. Be cautious that the evergreen type hybrids are not exposed to temperatures below 60 degrees or plants in flower may drop their leaves and buds.
Deciduous Orchids: Orchids such as Calanthe, Pleione, etc., are to be kept completely dry. There are a few, like Catasetum, Cycnoches, and a few others, that are kept moderately dry (this also includes Odont. grande).
Masdevallias: At this time the growth cycle starts, and repotting should be done. Keep cool, around 45 degrees both day and night, and provide plenty of air circulation and water. Fertilizer may be applied all year long, but at this time use 30-10-10 alternately with 10-30-20.
Vandaceous genera: Light, or the lack of it, becomes a challenge this month. Observe the growing area carefully to locate the brightest spots in the house where you can place your Vandas and Ascocendas. Do not make drastic transitions; instead gradually move plants from the darkest levels to the brightest upper levels to avoid leaf burn. Fertilize moist baskets or pots at lease twice this month if light levels are sufficient. Many of the popular Thai hybrids and the African angraecoids begin their winter flowering now, so watch for signs of inflorescence; “help” them away from the main stem of the plant to insure proper display. Maintain high humidity in the root zone, particularly for those plants in slatted baskets. Mist the roots daily with a light spray from a spray bottle or hose.
Check for red spider and thrips. Phalaenopsis type Dendrobium: Keep warm and watered all year long. On these species you have to be guided by their geographic origin. The Dendrobium group is so varied that no one set of cultural requirements fits all.
Information for these culture calendars is taken from The AOS Bulletin, Orchid Digest, a book Orchids and How to Grow Them by Gloria Jean Sessler and some of my own experiences.