FEATURESTORY
by Eric Hopper
Using Light Deprivation to Increase Harvests
G
reenhouse growers employ many differ-
ent techniques and products to increase
the production of their gardens. From fully
automated feeding systems to high tech
heating and cooling equipment, greenhouse grow-
ers are always on the lookout for anything that can
help achieve optimal results. Like indoor growers,
greenhouse horticulturists can realize higher quality
crops by having heightened control over temperature,
humidity, and air quality. However, one large advan-
tage indoor growers have over greenhouse growers,
is the ability to control the photoperiod (the length
of light per day). At least that was an advantage they
had, until greenhouse growers started implementing a
technique that allowed them similar control over the
photoperiod. That technique is known as light depri-
vation.
Controlling the Photoperiod
Light deprivation is exactly what it sounds like:
depriving the plants within the greenhouse of light.
This is accomplished by using a large shade cloth
that covers the entire greenhouse. Why would a
greenhouse grower want less light to enter his or her
greenhouse? The answer: to have control over the
6
photoperiod. Many plant varieties are sensitive to the
amount of light/dark they receive in a 24 hour period.
In fact, for many plants, it is the amount of light/dark
they receive that actually triggers certain responses,
such as the initiation of flowering or fruiting.
In a typical greenhouse, this natural response
to the light/dark periods will happen as the seasons
change and the days in the late summer get shorter.
The plants respond to the reduced light and increased
darkness by beginning to produce fruit or flowers.
When implementing a light deprivation technique,
a greenhouse gardener is able to mimic the shorter
days which occur in late summer and “trick” his or
her plants into flowering or fruiting earlier than they
would normally. This allows the horticulturist to have
ultimate control over when the plants will be har-
vested and to increase the amount of harvests he or
she gets per year.
Black Out Material
Unlike a typical shade cloth, which only reduces
the amount of light entering the greenhouse, the cov-
ering material used for light deprivation is designed
to keep out as much light as possible. The shade
cloth material sold for light deprivation is sometimes
www.GardenandGreenhouse.net
April 2018