If you don’t have a cold frame, making one would be a great
weekend project for any
gardener.
During winter, the cold frame will offer protection to
less hardy plants and newly
started perennials. It’s also an ideal place to overwinter
some plants or grow a small
patch of lettuce or other cool-season crop. It simplifies
the storage of bulbs and plants,
too, for midwinter forcing indoors.
 P. Sumner, UGA CAES |
| COLD FRAMES like this one can be built in a weekend. This bottomless box acts like a miniature greenhouse, protecting young or tender plants from temperature extremes. |
A cold frame is simply a bottomless box with a clear
glazing or covering to let in
light. Some gardeners make cold frames lightweight so they
can move them from one section
of the garden to another.
You can build frames from a number of materials. Wood and
cinder blocks are the most
common. Never use creosote-treated wood or wood treated with
pentachlorophenol or any
other material that could be harmful to you or to growing
plants.
Wood frames aren’t hard to build. You can buy an easy-to-
assemble kit. Some kits even
contain automatic ventilation equipment.
Ventilation is most critical in the fall and again in
late winter and early spring on
clear, sunny days above 45 degrees. Partially raise the sash
then to keep it from getting
too hot inside the cold frame.
As the fall progresses, you may have to add extra
insulation to the cold frame to
reduce extreme drops in temperature. Straw, bags of leaves
or foam insulation boards all
help control the temperature in the cold frame. Or just
stack bales of straw or hay
against the frame.
Some people like to experiment by using containers of
water to absorb solar heat during
the day and release it slowly at night. They make the cold
frames larger to include the
water containers.
While this may be useful in managing temperatures,
remember that it won’t help protect
tender plants, which will need to be moved indoors if they
are not cold-hardy.
Sinking the frame into the ground somewhat will provide
protection, too. It will use
the earth for insulation.
To make using the frame simpler, provide a walkway to the
front, leave enough space
behind the frame to remove the sash, and add weights to make
raising and lowering glass
sashes easier.
Unheated frames are useful for much of the year because
they collect heat from the sun
through the panes.
To make the most of the heat and light, put the cold
frame in a southern or
southeastern exposure with a slight slope for good drainage.
A sheltered spot with a wall
or hedge to the north will protect against winter winds.
