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.