A black 5-inch corrugated drainage
pipe is laid between rows of tender seedlings and filled with water which
gets heated by the Sun. Heat is released to the cooler night air.
If a frost is likely, a cover draped over the pipe and nearby plants can
keep them "snug as a Bug" in their Tent.
This Solar Heater can give you
early Tomatoes and Cantaloupes
by foiling a late Spring Frost.
This Heater is also beneficial
when there is no Frost predicted, since many plants fare better in an environment
that does not have major temperature swings. If you have similar plantings
without the benefit of this Heater, chances are they will be less productive
than these that get the heat.
An automatic feature is that
the colder the air, the more heat is released: if the water is 90F. and
the air temperature is 90F. there is no heat released. But if the air temperature
drops to 70F., then heat is released until the water is also 70F. The same
as when the air temperature drops to 50F. or 30F. It is not unusual for
the water to get much hotter than the air temperature.
The ends of the pipe must be
elevated to confine the water. Here they are wired to 6-inch mesh square
Tomato Cages, but twin stakes would serve as well. The corrugations double
the surface area, which equates to a smooth pipe twice as long. This allows
the water to heat up quicker. The ends are capped to keep out egg-laying
What works in the Spring time
also works in Fall. This Heater can extend your harvest by thwarting the
first light frosts which usually wilt your tender plants. The Pipe can
be left in place until after the vegetable harvest, but you may want to
drain the water out to stop the heating action if the night air temperature
approaches 70F. and refill it as the Autumn chill approaches.
You can use any heat source
that provides a little warmth to covered plants. Sometimes a degree or
two will make the difference between plants that survive a "cold snap",
and those that don't.
Maybe just a plastic, or woven
cover will do. Or a 100-watt light bulb, or maybe 2 or 3. Or a properly
grounded and protected thermostatically- controlled portable electric heater.
Or an adjacent Compost pile.
Or a helpful sleeping pet.
Also see Garden