When the days start to shorten and
night temperatures dip, do you often look over longingly at your neighbour's
greenhouse, wishing you too could keep plants producing into the fall?
Investing in a greenhouse, especially a heated one, is an expensive step. For
those of us who aren't quite ready to make the leap, there are a number of
inexpensive options to protect plants from wintry weather.
Cloches
and cold frames can help extend the harvest of summer crops into fall, keep
cool season crops growing through the winter, and help plants get a good start
in the spring. They can protect plants from moderate frosts, and increase
daytime temperatures by 5-20 degrees F.
Cloches
Originally,
cloches were constructed out of glass bell jars and were used to protect
individual plants. However, glass is fragile and expensive. You can make
similar cloches out of plastic pop bottles or milk jugs. Cut off the bottoms,
take the lids off, and place them over individual plants.
If
your plants are too large or you have just too many you can adapt this method.
A cloche can also be constructed using ½" PVC pipe and sheets of plastic
at least 5 feet wide and about 10 feet long. Cut 4 pieces of pipe into 5-foot
lengths (angle the cuts) and bury each end into the soil at least 6 inches so
that you have what looks like a series of crochet hoops. Space each pipe about
3 feet apart and then drape the plastic over them. You can secure the plastic
by weighing down the ends with bricks or rebar or clip the plastic right to the
pipe with large bulldog clips. Alternatively, you can use 10-gauge wire instead
of the PVC pipe.
Cold
frames
Cold
frames are very much like mini greenhouses but with solid sides. They can be
constructed using storm or sash windows and a simple wooden box or bricks for
the base. No bottom is required which enables you to just lift the cold frame
and move it around your garden. One trick to keep in mind is to make sure that
the back of the box is about a foot higher than the front so that you can angle
the lid and take advantage of as much sunlight during the winter and early
spring.
Floating
row covers
Floating
row covers, often sold as Reemay or Agrofabric, are made of spun-bonded
polyester or spun-bonded polypropylene. The fabric allows light, water, and air
to move through but enables you to have 2-8ยบ of frost protection. The row
covers are available in a variety of weights but for frost protection, 0.5
ounces per square yard is the minimum requirement.
Although
the fabric is light enough to "float" over your plants, winter winds
can cause abrasion so the cover should be supported with wire hoops or short
stakes. To prevent the cover from blowing away, the ends should be weighed down
with stones or buried right into the soil. Remember to leave enough slack to
allow room for your plants to grow.
The
lifespan of the row cover is usually 2 seasons. When the fabric becomes a bit
too ratty, use it to help germinate seeds. Placed over bare soil, row cover
fabric acts as a mulch, keeping the soil moist and raising the soil temperature
slightly. Seeds germinate very well in these conditions.
There
are few points to keep in mind before deciding which method of season extension
to choose.
1.
Temperature differences - plastic will
raise temperatures much higher than row covers. While plastic is great for
winter lettuce, cool season crops like cabbage and kale don't need such high
temperatures.
2.
Materials - not all plastics are alike.
Make sure the material you use is UV treated and at least 3 mil. thick.
Non-treated plastic will degrade and crack within just one season.
3.
Moisture - If you use glass or clear
plastic over your plants, remember that water doesn't come through and they
will need watering from time to time. Floating row covers don't have this
problem.
4.
Ventilation - On sunny days in the
early fall, it's easy for temperatures within cloches and cold frames to go up
more than 20 degrees over ambient temperatures. Ventilation will not only keep
temperatures moderate, but it will also help bring down humidity.
