October 2011 - Fall Adjustments

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Whether you are an indoor grower or grow in a greenhouse, Fall is the time to review your current culture and make appropriate adjustments. Depending on where you live, air conditioning will soon be replaced by open windows inside and cool breezes in the greenhouse. These changing conditions provide many different signals to your orchids, which may require some changes in your culture.

It is, or soon will be, time to move the cool-loving cymbidiums into more light. Southern growers of cymbidiums often keep their cymbidiums in dense shade during the heat of summer, moving them into increasing light levels as the days get shorter and nights get cooler. If cooled gradually, this group of orchid can even handle frost. Many cymbidium lovers claim that they get the best flowers when there was frost on leaves earlier in the season. Depending on location, cymbidiums may be left outside most of the winter and only protected when temperatures dip below freezing. Be sure, however, that you do not include the tropical cymbidiums in this frosty exposure as they require temperatures more similar to phals.

Many tropical orchids respond to lower night temperatures by switching from a growth cycle to a blooming cycle. Phals need a week or so below 65 F to initiate spikes and cymbidiums like it even cooler for a longer period. If they receive warm sunny days and drier growing conditions, these warm loving orchids can tolerate lower temperatures than suggested by the literature. As a general rule, tropical orchids can handle lower minimum temperatures than suggested.

Seedlings are an exception to the rule in that we want to get the maximum growth from them each year. Seedlings of all genera should be kept warmer now than mature orchids if you want to keep them in the growth mode. The exceptions are species and hybrids that require a dormant period, e.g. catasetumes, mormodes, etc. Fertilizers may also be used on seedlings if the orchid does not require a dormant stage. Be sure to reduce watering, even for seedlings, as there will be less drying because of the lower temperatures and light levels.

Indoor growers may have a difficult time providing the proper stimulation to initiate flowering if your home is maintained at a constant temperature. The most frequent question from indoor growers is how to get their orchids to bloom. Often the lack of flowering is caused by interior lights making day length too long or lack of temperature change with the season. Successful indoor growers often leave windows open or move orchids to a porch as the seasons change to provide the propoer stimulus and initiate a seasonal response to get flowers.

In the Deep South, vandas and their kin have been grown under trees all summer. When should they be moved and protected? There are a few species and even hybrids that enjoy nights in the 50s, but not many in this group. Most vandaceous species and hybrids need to be kept warm to keep them in a growth mode. Ascocendas, if they are relatively small, can be moved into south facing windows and bloomed successfully. The same can also be accomplished in an enclosed, sunny porch. If the porch is unheated, but enclosed, a small electric oil heater placed under vandas on a porch will work well to keep orchids warm on cool nights.

Be sure any orchids brought in from the outside are examined for bugs and disease. Pots are great hiding places for roaches, slugs and a variety of other pests that should stay outside.