A greenhouse
can be the avid gardener's best friend during the
fall and winter months. Greenhouses make it possible
for us to extend the lifespan of our valuable plants,
and sometimes even overwinter them so they can enjoy
yet another growing season next year. If
you already own a greenhouse or
are thinking of buying one, there are several
important things to consider when it comes to
prepping your greenhouse for winter
use.
The primary consideration in winter use of any greenhouse
is your local climate. How cold does it get in your area?
If you experience harsh winters full of snow and ice, using
your greenhouse all year long will be very difficult and
possibly quite costly. If your region experiences milder
winters, with nighttime temperatures sometimes dipping near
the freezing range, extended winter use of your greenhouse
will be easier.
It's also important to ask yourself, what types of plants
will you keep in your greenhouse during the winter months?
What range of temperature do those plants require? In
general, you want to overwinter plants that can tolerate
some fairly cool weather. Warm weather tropical plants that
are very sensitive to the cold will not do well in an
outdoor greenhouse during cold winter months.
Once you've determined the type of plants you'll be growing
and the lowest possible temperatures of your local area,
you're ready to consider alternate heat sources for your
greenhouse. Remember, daytime temps in a greenhouse will
usually reach 20 to 40 degrees warmer than the outside air.
At night, however, the air inside the greenhouse will fall
to about the same temperature as the cool night air
outside. This is the time when you have to protect your
plants from possible freezing in your greenhouse.
If the nighttime temps will only dip to the 50 or 60 degree
range, and you have fairly hardy plants in your greenhouse,
you may not have to provide any alternate heat source at
all. A very easy and inexpensive way to provide a little
additional heat is to place several very large rocks or
buckets of water inside the greenhouse. During the day, the
rocks and water will absorb the heat from the ambient air.
At night, they will then radiate that heat back out into
the greenhouse.
If you're dealing with much colder nighttime temperatures,
such as into the freezing range, you'll likely have to
bring in some small electric heaters. Look for a portable
heater that is specifically designed for use in
greenhouses. Such heaters will usually feature thermostats
and auto on-off switches that are programmable. A
greenhouse heater is also designed to run for quite a few
hours at a time, if needed, without overheating.
Last but not least, if you do have some snow accumulation
in your area, be sure you remove the snow from your
greenhouse as quickly as possible. Snow on the roof or
sides of your greenhouse will reduce or completely
eliminate any possible solar gain during the daytime.
Furthermore, if you get too much snow on top of a
greenhouse, even one that isn't in use in the winter, you
have to worry about snow load on the roof and possible
damage to the structure. In any case, it's always a good
idea to keep snow brushed off the roof on a regular
basis.
As you can see, greenhouse gardening during the colder
winter months isn't impossible, particularly if you live in
a mild climate. With a few simple steps and some
pre-planning, you'll be well on your way to raising
beautiful plants the year around.