The use of shading
is important in climates such as where I live Texas, USA. Many of my
trees would not survive the extremes of heat and humidity without it.
Many Tropical species will not tolerate direct sun either, as they are
naturally understorey trees in their native habitat, where they are
shaded most of the time by larger overhanging trees in the jungles of
Asia and South America.
The shading cloth
allows sufficient light for growth to reach the trees whilst protecting
them from direct sunlight. Trees left in direct sunlight in Texas (and
other similar climates) can become severely heated and burnt. Leaves
can become desiccated (dried out) as water is so quickly evaporated
in the heat. Pot and soil temperatures can rise to the point where continual
watering is necessary to avoid permanent damage to the roots.
The material itself
is usually graded by the percentage of light allowed to infiltrate,
ranging from around 40% to 80%, the former being more suitable for areas
of moderate summer climates and temperatures in the upper 80°'s F -low
live in SE Texas in the central United States, with temperatures reaching
the mid 90's to 100s, and have found a 60% range works best under most
situations, lowering the temperature underneath by as much as 10°F.
The exception might be some of the less heat tolerant species such as
Acer palmatum (Dissectum / or cut leaf varieties in particular). These
need full shade throughout the mid to late summer months, as they suffer
severe leaf scorching to the point of defoliation. More shade would
be required for example in a desert condition with 100°F temperatures
as the rule rather than the exception, so 80% or more would be a better
choice. You may also further fine-tune it by doubling up a lower grade
to achieve something in between.
material can be obtained at many major garden suppliers. I've also found
it available at many greenhouse suppliers. There are different versions
and methods of manufacture available, but they all accomplish the same
end results. In some cases, the expense and trouble would be of little
benefit to trees, particularly in milder Northern climates where no
protection is needed at all and could actually impede light and therefore
growth. In other situations, heavily wooded locations with many large
trees overhead, it may also be unnecessary.
In conclusion, the
level or lack of shade required, should be given on an individual species
basis, given the needs and heat tolerance of each tree species.
Here follows an
example of how I construct my shading each Spring;
After determining the dimensions
of the shade material, I began the layout of the frame work, in this
case PVC pipe in a 1" diameter sizing it to allow 4-6" extra
on all sides of the cloth. I choose this medium for the framework, for
it's lightweight and strength.
will need to ensure that the frame is kept square, and to prevent warping
while attaching the material, I used a series of pipe fittings at the
corners to form cross braces on the diagonal.