referred to as “black out” material or 100% shade
cloth. There are different types and qualities of light
deprivation shade cloth, including varieties that are
“breathable” or ones that contain multiple layers. The
“breathable” fabrics are typically reserved for inter-
nal light deprivation systems (where the shade cloth
is within the greenhouse, not outside of the glazing
material). A breathable fabric will help avoid conden-
sation drips that may occur after the shade material is
removed for the day. External black out cloth is the
shade material that covers the greenhouse on the out-
side of the glazing material.
The temperature within the greenhouse can be
infl uenced by the type of shade cloth material being
used. The blackout material which is the most effec-
tive at reducing excess heat is one made of multiple
layers of fabrics, including a white layer on top.
When the greenhouse is “blacked out”, the white
layer refl ects the sun away from the greenhouse,
helping to reduce the amount of heat that builds up
within the greenhouse. The shading material used
for light deprivation needs to cover the entire green-
house structure to ensure complete darkness. Each
day the blackout material is removed for the desired
amount of light hours. After reaching the desired
length of light hours, the shade material is manually
or automatically put back on the greenhouse.
Manual or Automatic
With a manual light deprivation greenhouse, the
shade cloth must be manually positioned over the
greenhouse structure. As can be imagined, this can be
quite diffi cult with large structures. Gardeners usually
rely on some sort of rope and pulley system to aid in
moving the potentially heavy shade material. Aside
from the physical labor involved, the biggest disad-
vantage of a manual system is that someone must be
present every day for both the covering and uncover-
ing of the greenhouse. Forgetting just once can cause
problems for the greenhouse, including out-of-whack
atmospheric conditions or stunted growth due to
quickly alternating photoperiods.
An automatic light deprivation greenhouse is
one equipped with a motorized system for situating
and removing the light deprivation material. These
systems are typically equipped with a small electric
motor. These motors can be wired for use with a
chain of car batteries to operate in locations with-
out access to electricity. Automatic light deprivation
systems allow a gardener to automate the system’s
motor with a timer. This means the horticulturist does
not have to be present every time the covering is re-
moved or put back onto the greenhouse.
Heightened Control with Light Deprivation
The biggest advantage of using a light depriva-
tion greenhouse is the heightened control over ini-
tialing the fl owering or fruiting of the crop. Before
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www.GardenandGreenhouse.net
April 2018