This is reprinted from an email sent by Martin’s son. Martin has always been generous about sharing information in the past and is in India right now so I can’t get explicit permission to reprint, but he has always said “yes” before when I asked…
Much of the information comes from Martin’s book, “Florida Orchid Growing: Month by Month” which can be purchased at this link from the publisher.
Martin publishes a monthly newsletter to which you can subscribe at this link.
The newsletter and book are both highly recommended with information tailored to our South Florida growing conditions.
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Dear Readers:
As you know, this week’s temperatures are dropping to dangerous levels for our beloved orchids. Martin and Mary are still in India, but they asked me to send out the relevant information from Martin’s book Florida Orchid Growing: Month by Month.
The page numbers are included for easy reference for those of you who already own Florida Orchid Growing: Month by Month.
Additionally, I have included an excerpt from the forthcoming
Cultivo de orquídeas en Florida — Mes por Mes, available this January, for Spanish speaking friends and family of our readers. Thanks again to Pro Translating for wonderfully translating Dr. Motes’s book into Spanish.
We’ve also added social media share buttons to the top of the email, so you can easily share this information with your friends via Facebook and Twitter.
Good luck with the cold!
Bart Motes
(Excerpted from Florida Orchid Growing: Month by Month page 113, all rights reserved)
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 chapter, 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.
For more expert advice like this, click here to get your own copy of Florida Orchid Growing: Month by Month.
Cold Temperature Tolerance of Different Orchids
(Excerpted from Florida Orchid Growing: Month by Month pages 117-120, all rights reserved.)
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 50º F (10º C) 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.
For more expert advice like this, click here to get your own copy of Florida Orchid Growing: Month by Month.
Dendrobiums are among the most confusing for new orchid growers. This huge genus, well over a thousand species divided usually 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 D. anosum 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 truefor 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 60º F (15º C) 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 30s (3-5º C). Section Formosae, D. formosum, D. infundibulum and the new hybrids prefer slightly warmer conditions but are quite happy with temperatures in the 40s (6-9º C). 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 50s (12-13º C). A few exposures to temperatures below 60º F (15º C) 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.
For info on other sensitive plants get the book!
Vandas come next on the scale of sensitivity….
Oncidiums of the “mule ear” type with thick fleshy leaves (O. luridum, lanceanum etc.) have warmth requirements similar to vandas…..
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 40s (8-9º C). They must, however be protected from both frost and freeze….
Forecasts of temperatures below 40º 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 like a lacy Mantilla holds in a surprising amount of heat. Under screen, a fine mist head (½ gallon per minute) 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 off any light frost settling in. Growers with swimming pools frequently turn on the re-circulating 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 make 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 32º F and a light frost is just the ticket for great bloom. Keep the water off these!