Cool weather is here for most of us. Even South Florida is experiencing lower daytime temperatures and cool nights. The shortening day length and cooler nights initiate all sorts of changes in your orchids.
Many fall blooming cattleyas are getting ready to bloom and buds are swelling in their sheaths. C labiata, C bowringiana and the fall blooming form of C skinneri, and their hybrids typically have double sheaths. It seems that the big change in day to night temperatures can cause moisture to accumulate between the inner and outer sheaths causing buds to rot. Watch these orchids carefully and be sure there is lots of air movement around these orchids. If you observe any moisture accumulating, carefully open the outer sheath and allow air movement into the space between sheaths. That usually solves the problem.
Vandas are known as heat-loving orchids, but have always bloomed better
for me in the fall and winter as long as temperatures do not get below
60 F and there is enough light. Colors are always brighter when nights
are a little cooler. This is especially true for any Vanda or Ascocenda
with Vanda coerulea in the parentage.
Cool weather is here for most of us. Even South Florida is
experiencing lower daytime temperatures and cool nights. The shortening
day length and cooler nights initiate all sorts of changes in your
orchids.
Many fall blooming cattleyas are getting ready to bloom and buds are
swelling in their sheaths. C labiata, C bowringiana and the fall
blooming form of C skinneri, and their hybrids typically have double
sheaths. It seems that the big change in day to night temperatures can
cause moisture to accumulate between the inner and outer sheaths causing
buds to rot. Watch these orchids carefully and be sure they have lots of
air movement. If you observe any moisture accumulating, carefully open
the outer sheath and allow air movement into the space between sheaths.
That usually solves the problem.
Vandas are known as heat-loving orchids, but have always bloomed better
for me in the fall and winter as long as temperatures do not get below
60 F and there is enough light. Colors are always brighter when nights
are a little cooler. This is especially true for any Vanda or Ascocenda
with Vanda coerulea in the parentage.
Phalaenopsis require a significant day to night temperature change to
initiate spikes. It usually takes a couple of weeks of these conditions
to get all of the phals in a greenhouse to put their energy into growing
spikes instead of leaves. Phals will be fine on a porch or in a
greenhouse even after nights are in the upper 50s F as long as the day
temperature rises above 80 F. Once daytime high temperatures are below
78-80 F, phals need to be kept no lower than 60 F at night.
Paphs and phrags really seem to love the cool nights too. Mature
growths, especially in the multifloral paphs will prepare to flower.
Usually development of new growths is the first sign that a flower spike
will soon emerge.
Essentially, I stop fertilizing cattleyas (except seedlings) starting in
October and reduce watering frequency, but not watering intensity. Less
light and heat each day means that orchids dry out less rapidly. Pay
careful attention to periods of clouds and rain, which can also lead to
less need for water.
Some books recommend switching to high phosphate fertilizers for phals,
paphs, vandas, and other orchids that do not have a rest period before
flowering. For years I did this, but finally decided that maintaining a
high nitrogen fertilizer gave me better flowers and more of them.
Because watering is reduced and fertilizer is provided with each
watering, there is a reduction in fertilizer, but that is the only
change.
Cymbidiums are not widely grown in the Deep South, but can do well here.
If you have some of these genera, now is the time to move them into
increased sunlight. Best results occur when Cymbidiums are kept under
heavy shade during the intense summer heat. Now, give them a good shot
of fertilizer and slowly move them into the sunlight. Unless you have
one of the tropical forms, they can take temperatures near freezing and
seem to bloom best when they have a light frost on their leaves at
sunrise. Once you see bloom spikes emerging, protect them from extreme
cold until they flower.