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July in Your Orchid Collection

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July Climate Data

  • Average high: 90.9

  • Average low: 76.5

  • Average mean: 83.7

  • Average rainfall: 5.79"

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

    Although it mostly passes unnoticed to millions locked in their air-conditioned bubbles, July in South Florida is quite different from June. While the pattern of afternoon showers built from the moisture of the morning’s sea breeze persists in July, the thunder-storms are sharper and shorter. The clouds linger less and the foliage dries more quickly. Less quantity of rain falls in July than in June and periods of several days typically pass without a drop. This is good news for orchid growers. July (and August) allow orchidists to focus on the first essential of orchid growing, drying the plant out.

            Frequently, neophyte growers ask “What if I go away for several weeks in the summer and there is no one to water the plants?” The response is “That’s wonderful”. Experienced growers use the break in the rainfall during July and August to dry their plants “hard”. Depriving orchids of water for several days until they and the media or baskets they grow in are bone dry is essential to good orchid culture. By drying the plants hard, one deals a severe blow to orchids natural enemy, fungus. Orchids have evolved to withstand drought because fungus can not. During severe drought fungus’ only defense is to cease all growth and retreat into a spore stage. Hopefully (and with good cultural management) these pathogens will not be aroused from this slumber until the first drizzle of September sets in, allowing our plants two months to mature and harden their growth making them less vulnerable to the September conditions which give some advantage again to the fungi.

            Careful watering and judicious drying will do more than any other practice to ensure healthy plants. Drought is the orchid plants armor against disease. Be sure that your plants dry as completely as the weather of July permits. Nonetheless, as our plants are in full growth they need adequate water in July therefor after a hard drying, orchid plants need a thorough re-hydration. If the next rain fall is insufficient to saturate pot, roots and media, the grower should add to the natural moisture until he is sure both roots and media are saturated, using two or three applications of water spaced a few minutes apart. When the plants stop dripping is the time to apply the next dose of water. Don’t stop watering until the “heft” of the pot tells you that it is holding as much water as it can. More typically in July, orchidists should use these opportunities when more moisture is required to substitute fertilizer for water and saturate the roots and the media in the same thorough manner. In July typically think of fertilizing rather than watering. Weekly application of a commonly available balanced fertilizer (20-20-20 or 18-18-18) at two teaspoons per gal. will supply the nutrients that our plants require in this period of lush growth. This balanced formula should be alternated every other week with potassium nitrate and Epsom salts (one tablespoon each) to supply the extra magnesium and potassium we now know are plants need on a regular basis. Even better (although not so readily available) lower phosphorus fertilizers containing extra magnesium and calcium with a formula like Peter’s Excel (15-5-15) have been shown to be the precise fertilizer our plants need. This formula is recommended year round. Hopefully such orchid specific fertilizers will become more widely available. Lowering the phosphorus intake of our plants is particularly important in South Florida because of our alkaline water. Always apply fertilizer in the same way as water, in two to three doses spaced a few minutes apart. Apply the fertilizer to the point of “run off” IE.when the solution starts to fall off the plants; stop and move on to the next plant. Repeat the application a few minutes later when the plants stop dripping. In July more than ever, never, never follow the frequently heard and disastrously bad advice of watering before fertilizing. Always substitute fertilizer for water: now and at every season. Roots saturated with water cannot absorb fertilizer but the prolonged wetness can rot your plants. Don’t give fungus the upper hand by wetting the plant’s foliage and roots more often or longer than necessary. Careful watering is especially important throughout the rainy season.

            The wise orchidist will have long since finished all of his potting of sympodials and the top working of his vandas but for the rest of us this is the eleventh hour. Autumn is closer than we think and vandas will need at least three months to settle in to their new baskets or pots before the first chill of October tickles their root tips. Unless you can protect them thoroughly from cold, Vandatop cuttings and keikies should not be made after the end of July. If you do take cuttings remember the “3 root rule”. Count down from the crown and make the cutting beneath the third or fourth root. Keep as many leaves as possible on the stump and you will be rewarded with a greater abundance of offshoots. Always slip the sterile knife or shears down between the stem and the leaves and then cut transversely to save as many leaves as possible. Be sure to anchor the cutting firmly in its new lodging. Tie them up and tie them down! There is no time for mistakes in July.

            Thrips are much less of a problem in July as the rain tends to wash them away and doubtless there is an abundance of other lush fodder for them elsewhere in our yards. They can reappear in a prolonged patch of dryness, so if you need to think of watering in July it may be dry enough to worry about thrips. A prophylactic spraying for thrips in July will also put a damper on scale crawlers. If a second spraying with soap follows the first by seven to 10 days, the population of mites will be scotched as well.

Treating Cold Damaged Orchids

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Cold damage appears on orchids as whitening of the foliage and stems. The white gradually turns to brown as the effected tissue dies. Often this dead tissue simply dries and the damage is limited to the unsightly patches that are left. Frequently, however, the damaged tissue is infected with bacterial rot which can spread in the plant and cause further damage. 
 
Softening of the edges of the cold damaged areas or oozing of brown fluid indicates bacterial infection. Removal of the leaf or stem is a simple but somewhat drastic solution. If one is loath to lose so much of the plant, the most effective treatment for bacterial infection is treatment with cupric hydroxide (Kocide or Champion) which should if possible be combined in equal parts with mancozeb (Manzate or Dithane M45). 
 
This combination is packaged, pre-mixed as Junction. By adding a small amount of water to the chemicals in a jam, one can make a slurry that can be brushed on the lesions.

Be cautious when making the slurry not to inhale any of the dust and never, never, dust these chemicals without wearing a mask.

An old toothbrush is efficient in applying this and your dentist will be happy to have it out of your mouth. Any left over slurry can be placed on a high shelf (brush and all) and re-hydrated later. This stuff is also the cure for those soft spots that appear on Phal. leaves in summer. 
 
For large collections, with extensive damage, one tablespoon per gallon of cupric hydroxide and mancozeb can be sprayed. Mix the two and wait an hour or more before spraying. Do not apply this mixture to dendrobiums which are hyper-sensitive to copper or to bromeliads (ditto).

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.

Treasures from the Storm

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Excerpted from Florida Orchid Growing: Month by Month page 126-127 by Martin Motes. All rights reserved.

It's an ill wind that blows no one any good. Minor hurricanes are still a major nuisance but small blessing can nonetheless flow to South Florida orchidists in the enforced pruning of our trees which will bring cherished light to our orchids. The prunings themselves are a major resource for the clever orchidists. The streets of South Florida are typically lined with a virtually inexhaustible lode of great orchid mounting material in the wake of minor hurricanes. All that is needed is the energy to cut and haul the appropriate branches that will supply years of great orchid mounts. With such an abundant (dare I say windfall?) one can even be quite picky. The savant orchidist should select his material with an eye to the best suited and the most appealing. Three species stand out. First, the golden trumpet (Tabebuia argentea or caribae) whose cork like bark is ideal for most orchid genera is always the first to fall and particularly abundant in roadside plantings. 

Live oak (Quercus virginiana),a favorite host of our native epiphytes, is also highly favored by epiphytic orchids in general and dendrobiums in particular. It is, of course, of the very same genus as cork itself and the wood is highly durable. 

 Next among the commonly fallen and desirable is button wood (Conocarpus erecta) both green and silver, again a favored host of native epiphytes. These branches is "driftwood" on the hoof. It is the roots of this species that become the "driftwood" of orchid culture. The branches are great mounts too.

Other species such as bottle brush (Callistemon) are good but the three common storm victims will provide more than enough of the very best mounts. Look for branches that are forked or twisted or that have other distinctive turns that will add character to the finished mounts. 

 Try to imagine the plant situated on the branch. A small chain saw makes short work of these branches, quickly rendering them into raw works of art. A well sharpened double set hand pruning saw will do fine. Now would be a good time to acquire these tools if needed before they are inevitable truly needed in the aftermath of a major hurricane. When a "minor" storm has passed, we can count our blessings and collect the orchid manna falling from heaven.