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January in Your Orchid Collection

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  • Average high: 76.5
  • Average low: 59.6
  • Average mean: 68.1
  • Average rainfall: 1.88"

Excerpted from Florida Orchid Growing: Month by Month by Martin Motes. All rights reserved.

January is somewhat like December but in reverse, with each succeeding day bringing longer hours of sunlight until days are long enough that afternoons return at the end of the month bringing extra sunshine to warm us after the extra sharp cold snaps. January, like December, is cold and dry, in fact even colder and drier. Dry is good, cold can be very bad. We need to accentuate the positive by especially careful watering in January. By keeping our plants as dry as possible and spacing our waterings as far apart as possible, we conserve our potential to use water to protect our plants from the cold, keeping our powder dry, as it were. In January water early, water thoroughly when you do and do so sparingly. The cooler overall temperatures of January are much less dehydrating even to plants which have received less water. remember, many of our orchids come from seasonally dry and cool climates not so different from South Florida. Many orchids are equipped to handle the drier cooler conditions of our January. A good strategy is to “top-up” the light watering that our plants receive with the passing showers that each successive cold front brings. This slight additional irrigation may prove to be all the watering that many genera need. Such parsimony, preserves the possibility of using water on truly cold nights to warm our plants.
Water is the only feasible source of heat available to plants grown in the open, under trees, in shade houses or on patios in South Florida. Ground water here (and in most of the rest of the world is about 63 F. (16C). Water out of municipal systems is not far different. On truly cold nights turning on the water can be of great benefit to our plants, provided that they have not been over-watered in the days and weeks preceding, thus inviting the ever present fungi to do more damage than the cold. For this reason as well, in general, orchids are better off dry until temperatures approach frost or freezing. The logic for maintaining plants dry is not only to minimize fungal problems but also because cold air is typically very dry air. If plants are wet in very dry and rapidly moving air say 10 or more MPH, evaporative cooling can take place, chilling our orchids further and faster than they would if dry. When the water goes on it needs to be in heavy volume and it needs to stay on to keep the plants thoroughly bathed in its warmth. Very still air on the other hand, presents a different danger as frost is possible at temperatures higher than is commonly realized. In calm air frost can form at higher elevations and settle in on plants while the surface temperature is only in the upper 30's. The best forecast for nights when the temperature will hover near 40 is a light wind of 2-5 miles per hour. This light wind mixes the warm air near the surface and draws warm from the earth. Clear, cloudless, still nights with bright shining stars elevate the spirit but harbingers frost.
Forecasts of temperatures below 40 F should stimulate us to action.
If it is not practical to bring all the Phalaenopsis, vandas and hard cane dendrobiums into the house or garage, think of using water to help protect them. Shade cloth or even patio screen hold in a surprising amount of heat like an lacy Mantilla. Under screen, a fine mist head attached to a hose and left running beneath the bench or plant rack will provide several degrees of additional warmth that will often sufficiently temper the chill and ward of any light frost settling in. Growers with swimming pools frequently turn on the recirculating pump to keep a supply of warm water near the pool’s surface where it can add heat to the ambient environment. A few degrees of warmth frequently makes all the difference to our sensitive orchids. In more open areas not protected by a permanent irrigation system, an oscillating sprinkler at the end of a garden hose is very effective. These are readily available at Home Depot and garden shops for a few dollars. On frosty nights, start the water at bedtime and let it run until the sun is up. The extra water once or twice in a month will do no harm to orchids that have been properly and judiciously watered the remainder of the month. In fact, these occasions present the opportunity to be sure that excess fertilizer salts have been leached from the pots and medium. A good work can be born of necessity! 
Remember that Himalayan dendrobiums and ‘‘warm growing’’ Cymbidium hybrids will positively relish temperatures down to 32F and a light frost is just the ticket for great bloom. Keep the water off these!
In the drought of January, mites, which affect nearly all genera of orchids, continue to be a serious problem that will only get worse. They will reach a crescendo in March and April but January is a good time to scotch them. Paphiopedilum and other softy leaved genera are particularly susceptible but no genus is free of them. One theory on why deciduous genera such as CatasetumCalanthe and others lose their leaves hypothesizes that this totally rids them of mites. 
Being totally rid of mites is a good thing! Sometimes this is easier said than done because mites reproduce with such voluminous speed. Their life cycle from egg to reproductive adult being is as short as twelve days. In order to control mites one must achieve as total a kill of the population as possible. Total control can only be achieved with two successive sprays. After spraying for mites initially, one must spray again in 7 — 10 days. No single spray is totally effective in killing both adults and eggs and a second spraying is necessary to kill any survivors before they can reproduce. Oil as recommended in the December chapter at 1.5 oz per gal followed in7-10 days by soap at the rate of 2 oz per gallon is very effective. These treatments are also quite effective against scale and mealy bugs which thrive on drought as well. Be sure your plants are well watered the day before applying both oil and soap and be sure that you cover thoroughly all leaf surfaces especially the lower ones which are mites favorite hide outs.

For those who wish to be more aggressive, the University of Florida IFAS recommended chemicals for mite control are:
Avid 0.15 EC
Kelthane T/O
Mavarik Aquaflow
Talstar Flowable
Always follow label instructions for use. Any of the can be alternated with the soap or the oil in the 7-10 day cycle.
Controlling mites pays huge dividends! You’ll be surprised at the extra vigor your plants display.

Cold Watch
As cold is a major theme of this month, a review of some factors effecting temperatures in South Florida should be particularly valuable to new comers in the wide world of orchid growing.
    While we bask in the warm glow of a tourist board’s vision of winter, (made all the warmer by thoughts of our envious friends and relatives stuck in the northern snow and ice) we should be mindful that January can produce quite severe cold. The majority of hard freezes in Florida take place in January, and even short of that catastrophe, the month usually brings the coldest weather of the year. We need to keep a sharp eye on the weather reports while remembering that in our almost island of Florida a number of factors influence the severity of the cold which will impact us.
    First the shape of the cold front interacting with the shape of the peninsula. The weather that delights the tourist board and all of us while plunging most of the US into the throes of ice and snow usually result from particularly large, slow-moving masses of cold air that have spread across much of the continent before reaching Florida. Large broad masses of cold air that seep downward over a broad front also cover the Gulf of Mexico and the Atlantic as they progress southward. These tempering bodies of water bathe the cold to merely refreshingly brisk temperatures. More dangerous to our plants are the smaller, tighter, fast-moving fronts which plunge like a dagger of cold straight down the peninsula to the tropical heart of South Florida. Such fronts typically spawn the freezes and severe plant-damaging cold that is of the greatest concern to orchidists and other plant people. These Siberian Express fronts bring winds out of the Northwest that are un-influenced by the benign, protective bodies of water flanking the peninsula as they drive down the central landmass of Florida. When the winds from an approaching front start out from the southwest and move gradually to the northwest and then quickly to the north and northeast, we can expect cold nights and warm days that reasonably well-protected orchids not only tolerate but in some case actually relish. The more savage fast moving fronts where winds start in the Northwest and stay there are the ones to send us thinking of moving plants or providing additional heat.
    Wind direction is always critical in South Florida. Because of the peninsula’s decided eastward cant, winds from the north in much of South Florida are in fact relatively mild. North winds here are blowing across the warm Gulf Stream. The first shift to the northeast absolutely spells relief as the warm Atlantic has absorbed the cold.
    Wind speed is also important. Strong winds at low temperatures chill our plants more rapidly, exposing them to additional hours of chilling. “Wind chill factor” has no relevance to plants until the actual air temperature drops to a level unacceptable to the plant. After that, the more rapidly the plant itself’s temperature falls to that damaging level and the longer it stays there the worse the case. Wind speed enters the equation only if the final low temperature is below our plants’ tolerance. Wind breaks of vegetation or manmade are always to be sought. Native epiphytic orchids hide out in the most protected hammocks and sloughs. We can learn from them.
 Dead, still air looms with another threat: radiational cooling which can allow frost generated at higher levels of the atmosphere to settle in on our plants even when the air at the surface is only in the upper 30's. These frosts typically occur when the front has passed leaving such low humidity that there is no moisture in the air to retain ground heat which radiates quickly into the cold reaches of space. Light winds of 2-5 miles an hour are our friends on these nights. They stir additional heat from the ground and keep the colder upper air from settling in.
    Relative humidity also has a profound effect on temperatures. Dry, clear air allows heat to radiate out into space. Those bright starry nights are beautiful but as Good King Wenceslas knew they are not necessarily our comforters. The best measure of the dryness of the air relative to cold is the dew point. When water vapor is wrung from the air an incredible amount of energy is released and the heat of transformation raises the air temperature a degree or two. Because of this phenomenon, the dew point is usually the closest measure of the coldest temperature that will be reached in the night. Particularly on still clear nights it should be monitored closely.
    Wind direction, wind speed, dew point — where does one find these on a chilly night? At the Florida Agricultural Weather Network (FAWN), a system of automated weather monitoring stations, as close as your computer. There will be a station near you. There are also several at points north of the nearest location that give data on conditions that are effecting areas through which the cold front is moving toward us. FAWN is updated every 15 minutes here. Bookmark it for something other than worrying to do on those cold nights

December in Your Orchid Collection

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  • Average high: 77.5
  • Average low: 62.2
  • Average mean: 69.9
  • Average rainfall: 2.18"

Excerpted from Florida Orchid Growing: Month by Month by Martin Motes. All rights reserved.

December marks the beginning of the serious dry season in South Florida. While this additional dryness provides relief from the autumnal rains that can bring so many fungal problems, December is also the month of shortest day lengths. This contracted period of light, on the contrary, reduces severely the drying potential for our plants. Nature thus both gives and takes away from us in December. We must make sure, therefore, that we do not aid the dark side of the force by improper watering. In December, above all, one must stick strictly to the two cardinal principles of orchid watering: water early in the day so your plants have as many hours as possible to dry, and water heavily when you water, allowing longer intervals between watering to dry plants thoroughly. This practice maximizes the benefit of the dryer air of December and minimizes the adverse effect of the shorter day lengths.

            When nature has delivered a light overnight or early morning rain as she so often does in December at the leading edge of a cold front, add to her efforts by watering thoroughly that same morning and skip out watering for an extra several days afterward. With this method you can use the general dryness of December to give yourself much of the advantage of a greenhouse in terms of controlling watering. As in all aspects of orchid culture, keen observation is the key to success. In cooler weather your plants need much less water. Moreover cool air even at the same relative humidity, strips less water from your plants because cool air has less water holding capability. Always be sure that your plants really need water before you roll out the hose in December. Remember to use at least one of the standard tests for dryness: the finger dug slightly into the media test or the newly sharpened pencil coming dry like a knife from a well cooked custard, or test by hefting a pot that you know the weight of, both wet and dry and be sure that it has attained sufficient lightness. When you are sure they are dry, water them until you are sure they are very wet, then let the drying air of December do its magic to ward off leaf spotting diseases.

            Himalayan dendrobiums of the nobile and Callista (D. aggregatum, chrysotoxum, etc.) Sections require no additional water (beyond rain) in December. Remember, those of you who water (or, even worse, fertilize) these dendrobiums in December, will be punished by having your flowers taken away in the Spring. Some growers who have the space, isolate these dendrobiums along with other types that want hard drying such as Catasetum, Cycnoches, Mormodes, and Calanthe. Another strategy is to hang these plants high or at the edges of the collection reminding oneself to neglect them and also to avoid watering them by mistake. Some growers achieve the same result effect by turning the pots of these genera on their side in November or December, to avoid catching water from whatever source. Plants of some of these genera that have finished flowering can even be removed from their pots and stripped to bare roots in anticipation of re-potting them in new media when they break growth in the spring.

            Most sympodial orchids are resting in December and require less fertilizer. Biweekly or even monthly applications of a balanced fertilizer or 15-515 are still desirable. Nitrate nitrogen is the most readily absorbed in cooler weather; therefore at least one more application of the potassium nitrate/magnesium sulphate (at 1tbs. each per gal.) recommended in November is still a good idea. It’s good stuff! Vandas, Phalaenopsis and other monopodial orchids should be fertilized right through the winter although both the amount of fertilizer and the frequency of application can be reduced. Remember reddening of the foliage is not natural, nor is it a response to the cold per se but rather a symptom of nutritional deficiency. The plants are asking for more potassium and magnesium. Give them the groceries.

            December can be cold. Frost has occurred in the first week of the month and unforgettably, the coldest temperatures ever recorded in South Florida were registered on December 25, 1989. If you haven’t taken some of the precautions outlined in the November Newsletter, get busy! Keep a close eye on the forecasts during this volatile month.

 Remember that hard cane dendrobiums of the sections Spathulata and Phalaenanthe are the most sensitive of commonly cultivated orchids. They resent temperature much below 60 degrees F. Phalaenopsis are next most sensitive, then vandas. Protect all these genera more carefully.

            If you are getting a jump on Spring potting chores by repotting sympodial orchids that have finished blooming, it is particularly important that you take extra care in securing them in their containers. These plants may not be sending out new roots for several months, enough time for them to be shaken loose from insufficient staking. Passing cold fronts can bring brisk winds in December. When new roots start to form on insufficiently secured plants, wind moves the plant and chafes the new root tips off. Improperly secured plants are never able to root properly and slowly pine away. If you love them you must tie them up, tie them down. This is also especially true of mass produced orchids sold in Home Depot, K Mart etc. The soft, peat based media used to grow these commercially produced plants in the controlled environment of a greenhouse often does not provide sufficient purchase to secure the plants in the rough and tumble of a South Florida orchid collection buffeted by harsh winter winds. You probably should have already re-potted these into more durable medium but until you do, tie ‘em up!

            Keep those vandas, phalaenopsis and hard cane dendrobiums as warm as you can. Merry Christmas, Hanukkah, and Kwanza!

Cold Temperature Tolerance of Different Orchids

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One major obstacle for neophyte growers is in understanding the diversity of cultural requirements of various genera of orchids. Orchids are such a vast group of plants which have succeeded in nearly every conceivable habitat on earth, that knowledge of a specific genus’s cultural requirements, rather than a general knowledge of what “orchids” like, is necessary to successfully cultivate the various types. Most cultivated orchids come from tropical regions but differences in elevation and other geographic features of their native habits can mean dramatic differences in the response of orchids to various external conditions. Most emphatically these differences can be seen in different genera’s toleration of cold. While some orchids are native to regions where frost is more the norm than the exception, others are hyper-tropical plants for whom 50 F (10C) is far too cool. Knowing which is which is essential in a mixed collection of orchids. A great irony for beginners is to discover that their extra nurturing efforts to protect certain orchids have in fact done more harm than good.

            Dendrobiums are among the most confusing for new orchid growers. This huge genus, well over a thousand species divided into 15 sections, ranges over nearly a quarter of the planet. Found from western Indian all the way to Micronesia, dendrobiums inhabit an incredible variety of ecological niches. Ironically, the two sections most common in horticulture are diametrically opposite in cold tolerance. Section  Dendrobium, the soft bulb or “nobile types” whether in their pendulous forms like Danosum and aphyllum or in the upright types like D. nobile and its hybrids, positively relish the cold. Temperatures right down to frost are the best culture to produce the most prolific blooming of these plants. Without cold and drought stress in winter these plants will retain their leaves and produce an abundance of vegetative growths but few if any flowers. Stressed by cold and dried out properly these plants lose all their leaves and in spring the bare bulbs are covered in flowers. The opposite is true for the “hard cane” dendrobiums of sections Spathulata and Phalaenanthe. Loss of leaf on D. phalaenopsis types is usually indicative that they have suffered from too much cold. Temperatures below 60F (15C) can produce this undesirable effect. D. phalaenopsis and evergreen types should receive the maximum cold protection.

 Other sections of the genus have slightly different tolerances. Section Callista, D. farmerii, D. lindleyii (aggregatum) and their relatives can take temperatures nearly as low as the nobile types and will bloom all the better for exposure to temperatures in the 30's (3-5C). Section Formosae, D. formosum, D. infundibulum and the new hybrids prefer slightly warmer conditions but are quite happy with temperatures in the 40's (6-9C).  Other sections of Dendrobium in cultivation such as Pedilonium, Latouria, and the Australian hybrids of section Dendrocorne have slightly different requirements and those growing these more “exotic’ will succeed best in researching them. Try B. Lavarack et al. Dendrobium and its Relatives, Timber Press.

            After the cold sensitive “hard cane” dendrobiums, Phalaenopsis are the most tender of commonly grown orchids. Phalaenopsis will be strongly induced to bloom by temperatures in the mid 50's (12-13C). A few exposures to temperatures below 60F (15C) will produce the desired spikes and thereafter the plants will be happiest if they are kept above 60. One or two nights down to 50 or slightly below will do little harm but are to be avoided in the best kept collection.

            Vandas come next on the scale of sensitivity. Like Phalaenopsis they are stimulated to bloom with sharp drops of temperature into the 50s at night, especially when the temperature can be induced to climb into the 80's (27-32C) by day. Vandas will tolerate brief excursions into the upper 40's but are best keep above 50 degrees. Temperatures below 50 for very long or very often will produce the tinkling sound of falling Vanda leaves, turning the plants into palm trees. 52.

            Oncidiums of the “mule ear” type with thick fleshy leaves (O. luridum, lanceanum etc.) have warmth requirements similar to vandas. The thinner leaved Oncidinae will usually take temperatures into the 40's with aplomb. Many of the hybrids in this group have been bred to Miltoniopsis and to Odontoglossum to increase their cold tolerance. A caution with this group is the ability of wind to strip heat rapidly from their thin leaves. The cold tolerance of these will be much greater in still air.

            With the exception of some species of Amazonian origin like Cattleya violacea, most cattleyas can take quite cool temperatures. Most growers have few concerns for them even in temperatures down to the upper 40's (8-9C). They must, however be protected from both frost and freeze. Be extra cautious on those clear still nights when the temperature drops to the 30's (3-4C).

            In addition to the cold loving nobile dendrobiums, certain other genera from the high Himalayas such as deciduous Calanthe and Cymbidium species and hybrids, actual require quite cold temperatures to stimulate them to their best bloom. Even “warm growing, temperature tolerant” hybrid cymbidiums flower best when chilled repeatedly into the low 30's.

            All orchids tolerate cold best when they have proper nutrition. Avoid too much nitrogen which might stimulate too soft of growth and increase the dosage and frequency of application of both magnesium and potassium in colder weather.