MYTH: The Greenhouse Effect is responsible for faster growth
and better health.
FACT: The Greenhouse Effect is over-rated.
Although
there is some truth to the belief that the Greenhouse Effect is responsible for the trees' accelerated growth, research shows
that more of the accelerated growth is due to the lack of wind and the effects of phototropism. As wind speed increases above
seven mph, the tree's defense mechanism begins to shut down photosynthesis to prevent the tree from drying out. Without photosynthesis,
the tree stops growing.
Some manufacturers attempt to close off their protectors and shelters in order
to create a "mini-greenhouse" micro-climate. This "closed system" approach seldom achieves the intended
result and could actually be fatal to the tree. These manufacturers tout the benefits of this "closed
system" at the same time they warn growers to lift the shelters when the weather is unseasonably warm. That's because
the so-called greenhouse prevents the dissipation of heat and moisture. However, raising the shelter can create a "chimney
effect" that can cause the leaves to become dessicated.
A certain amount of heat and moisture is good
but too much of a good thing is a bad thing.
For photosynthesis to take place at a healthy rate, leaves must absorb
huge amounts of carbon dioxide from the air. Restricting air flow into the protector reduces inflow of carbon dioxide, and
that's simply not good for the trees.
Closed system shelters slow dormancy in the fall and
accelerates emergence from dormancy in the spring. While other trees around them are keeping pace with the change in temperature,
trees inside closed system shelters are not.
In the fall, the problem occurs when the temperature drops below
28 degrees Fahrenheit and remains there for several hours. By then the trees not "protected" by these shelters have
usually gone dormant and are therefore not adversely affected by the drop in temperature. Not so for the trees inside closed
system shelters. They freeze and often die. For that reason closed system shelters must be lifted each fall, even
though that's difficult because the shelters may be stuck in the ground.
Then, after these trees
have gone dormant, their shelters must be lowered to the ground to provide protection from winter weather. The procedure must
be repeated again in the spring; otherwise, the trees in closed system shelters will emerge from dormancy too soon.
If
that's not enough hassle, during the summer, when temperatures soar into the 90s for days on end, the trees will bake and
sometimes die, if the shelters aren't lifted.
