Winter, at least for those of us in Florida, came suddenly in
November. Freezing temps were widespread in the northern third of the
state. The first cold snap reminded me of an issue that seldom impacts
those of us in Florida; using cold water on our warm orchids. For me
now, this is not usually a problem because the water out of the hose in
my greenhouse is always warmer than the temperature in the greenhouse in
the early morning when I water. If, however, I wait until noon on a
clear day, I could damage sensitive leaves and buds by applying water
significantly colder than leaves. In the morning, the coldest the air
temperature in the greenhouse is 58 F and the water from the tap is 68
F, thanks to the fact that our water flows some distance in the warm
earth.
If your water is from a surface source, such as a lake or pond, be sure
you check the water temperature before watering. Water colder than 5
degrees F than the plant can cause damage to new leaves and buds,
especially on thin leaved or sensitive orchids, e.g. phals and jewel
orchids. Depending on your water source, the temperature can vary
greatly. Years ago, when I was using rainwater and there was a snow, the
temperature of my water was so low that I could not use it for over a
month, even though it was stored underground.
There is some good news this time of year despite heating bills. Thanks
to lower day temperatures, I am able to bring my heat sensitive species
and hybrids out from the dark areas and into more light. Even in a
greenhouse where day temps often top out around 100 F near the ceiling
in summer, there are places that stay cooler and where I put those
orchids.
My prize S coccinea and many of its 1st, 2nd, and 3rd generation
hybrids, e.g. Pot Gene Crocker, are put into heavy shade where they stay
at least a little cooler. Even some more complex cattleya hybrids that
have heavy doses of S coccinea can be surprisingly intolerant of
Florida’s heat. There is still stress on those orchids and some clearly
suffer, such as Phal parishii and Phal lindenii, but they survive and
then thrive during the cool parts of the year. If a species or many of
the parents in the background of a hybrid are from higher elevations,
there is the likelihood that high temperatures in summer will be a
problem.
A few years ago, I received some heat intolerant hybrids in clay pots
growing in New Zealand sphagnum. It was surprising how cool the outside
of the pots were in the heat of the day. It turns out that the key is to
keep the roots cool when the temperature is hot. Generally, high heat
leads to faster decomposition of the medium, so I was surprised to find
that the sphagnum lasted several years. When I finally repotted them,
the sphagnum was still fresh and just a little decomposed. When I asked
about the medium from the originator of the cross, I was told that it
was high quality New Zealand sphagnum.
This was totally different than the Chilean sphagnum that I had been
using on some orchids, which totally disintegrated after just six
months. For my prized, heat intolerant orchids, I now use New Zealand
sphagnum in new clay pots. I also found that flushing the pots with
rainwater at least once a month prevented the buildup of salts. In
addition, fertilizer on these orchids is minimal because I want to limit
the soft summer growth that always seems to come with high temps.