Is Root Zone Heating Really Necessary?
With proper root zone
management you can grow
tropical plants in 45°F
ambient air as long as the
root zone is in the 70s.
The benefits of root zone heating to help extend a plant's
growing season or increase plant yield have been recognized
and employed by gardeners for centuries. Growers have devised
hundreds of methods to keep plant roots warm and looked for
ways to heat the ambient air for plant foliage as well. The reasons
for keeping roots and foliage warm might seem obvious, but
the physiological processes occurring in the root zone are quite
complex and affect the growth and development of your plants
profoundly—in fact, what happens under the surface is far more
important than what happens above.
With proper root zone management you can grow tropical
plants in 45°F ambient air as long as the root zone is in the 70s.
Sound farfetched? It's not. The biochemical processes that sustain
a healthy plant are based on the root zone environment—the
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foliage propels the photosynthetic process and as long as the
leaf tissue does not freeze (it should not fall below 40°F for
sustained periods) and the root zone stays in the 65° to 80°F
range, you can grow plants in an ambient temperature of 45°F.
Many growers start seeds or small plants in cold frames, heating
the soil but keeping the air at cooler-than-normal temperatures.
Their efforts extend their plants’ growing seasons and—in some
cases—their yields as well, while conserving the energy normally wasted on heating the ambient air.
How does root heating benefit plants? First, you have to look
at the soil as a living entity, not just a substrate whose purpose
is to support and stabilize plants and act as a reservoir for water
and nutrients—the traditional soil science viewpoint. All living
things have a temperature ‘comfort zone’ that they are most
comfortable within. Living things that exist in environments
that fluctuate from cold to hot or dry to soaked, however, are
constantly under stress. Under ideal conditions, though, if the
root zone is properly maintained in a consistent environment—
where temperature, water and aeration remain within optimal
levels—the plant will be stress-free. Typical root environments
fluctuate constantly. They go from being flooded after watering to dry between waterings and from cold at night to warm
in the day—the living soil is constantly trying to adapt to this
ever-changing environment and so the plant roots do not function as efficiently as they could. If root zone environments are
maintained consistently in the comfort zone, however, plants
actually become more photosynthetically efficient—using all
the energy they produce to focus on efficient growth and reproduction. As the plants use energy more efficiently, they begin
to process nutrients better and they use light and water more
efficiently as well, with less ‘stretching.’ In short, the plants can
now utilize resources at the level of their needs, not in excess to
overcompensate for stress.
Temperature has an enormous impact on these processes.
There are a few basic concepts that need to be considered
when trying to understand the dynamics of root zone management of temperature. Soil science breaks up into three main
areas: biological, physical and chemical. The biological aspect
of soil science is concerned with the living constituents of the