By George E. Boyhan
University of Georgia
It doesn’t feel like it now, but the growing season is quickly
coming to an end. If you want to keep growing vegetables through
the winter, you may want to look into a greenhouse.
A greenhouse may sound expensive, but the principles behind it
can be anything from a sunny window to a cold frame to a
full-fledged, heated greenhouse. All can be used to extend your
growing season for vegetables.
Of course, if you live in south Georgia, you can still grow many
vegetables through the winter in your garden. This would include
crops like onions, collards, cabbage, broccoli, carrots and peas.
All of these can stand very cold weather, including some frost.
A sunny, south-facing window can be an ideal place to grow a few
herbs or leafy greens. For an even better environment, you may
want to install a greenhouse window that extends from the side of
the house. This maximizes the amount of sun the plants get while
remaining warm at night and allowing for convenient access.
Tasty treats
Fresh leafy greens or herbs can be tasty treats during the
winter. Herbs in which the leaves are harvested are best. Those
in which you harvest the roots or flowers are harder to grow
under these conditions.
A cold frame is another low-cost greenhouse environment you may
want to consider. This is an enclosed, unheated space, usually no
larger than 1 to 2 feet high. It’s usually covered with plastic
or glass and relies on the sun to warm it during the day.
At night, it may drop back to ambient nighttime temperatures.
Large stones or a container of water can help keep night
temperatures up by releasing heat accumulated during the day.
During sunny days, these enclosures can get quite hot even in
winter, so you may have to vent them during the sunniest
parts of the day.
Venting
Venting can be done manually or with a passive, solar-powered
venting device. These devices will open a vent when heated and
are adjustable to your temperature requirements.
For even greater temperature control, these cold frames can be
heated. Electric heating mats will add bottom heat to your plants
and seedlings and help prevent cold injury on the coldest nights.
Finally, for the Cadillac approach, get a greenhouse. These can
be inexpensive wood or PVC structures covered with plastic. Or
they can be glass-enclosed, sophisticated environments that can
even be an extension of your home.
Many companies manufacture home greenhouses of various designs
that can be free-standing or attached. Sunrooms that extend your
living space are really nothing more than greenhouses. These
rooms not only give you space for growing plants but can extend
the heated square feet of your home, adding considerable value to
your investment.
Unheated or heated
Greenhouses can be unheated or heated, but all should have some
method of venting during warm, sunny days. Many vegetables can be
grown in such a structure.
If it’s unheated, cool-season vegetables such as lettuce,
spinach, cabbage and broccoli will do well, and the enclosure
will protect them on the coldest nights while accelerating growth
with the heat from the sun on warm, sunny days.
With a fully heated and vented greenhouse, the sky’s the limit.
Do you want fresh tomatoes or cucumbers in the winter? You can
grow them in such a structure.
Space is usually limited, so you may want to look for smaller
plant types, like short-vine cantaloupes or patio tomatoes.
Trellising is a good way to maximize the space, too. In fact,
commercial greenhouse vegetable production relies heavily on
trellising to produce quality tomatoes, pepper, cucumbers, etc.
Nothing beats walking into a warm, moist greenhouse in the
winter. This can be a wonderful hobby with endless hours of
enjoyment, and vegetable production can be just a small part of
the possibilities.
(George Boyhan is an Extension Service horticulturist with the
University of Georgia College of Agricultural and Environmental
Sciences.)
