temperature of the floor is always cool,
either the surface has been insulated or the
plants had been raised off the floor. This is
very important because cold floors draw
heat from the containers. Plants germinate
and grow considerably slower when their
roots are cold.
There are a number of ways growers
insulate the floor. Styrofoam insulation,
which comes in sheets or rolls, has been
placed over the floors. This material has the
added advantage that it is very reflective,
so that any light hitting this surface bounces
back to the plants. Plywood is often placed
over a layer of insulating material. Plants
are raised off a floor using a table or
wooden boards. Shipping pallets provide air
spaces so the warm air circulating in the
room can reach the containers.
Heating the Roots
Cold roots slow growth to a crawl.
Heating cables or a heating mat made for
heating soil or containers keep the roots
warm. Some cables and mats have a built-
in thermostat to keep the temperature a
constant 70-75 degrees. Heating cables
and mats are available from many garden
shops. They are convenient to use and
consume only a few watts.
Growers use room temperature or
lukewarm water to irrigate the plants so that
the roots are not shocked and cooled down.
They use lukewarm tap water, or heat the
water in the reservoir. Small reservoirs (up
to 100 gallons) are warmed using an
aquarium heater and thermostat. Larger