Hydrolife Magazine April/May 2017 (Canada Edition)

The popularity of light deprivation cultivation
has been on the rise over the
past few years. There are several reasons
why, but key factors include higher-quality
yields and off-season harvest times,
allowing growers who utilize this method
to supply the market with a particular
product when others can’t. In light deprivation
growing, growers use sunlight to
fuel their gardens while simultaneously
employing environmental controls not
seen in traditional outdoor grow scenarios.
This blend of cultivation styles allows
light deprivation gardeners to combine
their knowledge of indoor and outdoor
growing to produce exceptional crops.
Furthermore, light deprivation requires
less electricity and allows for harvests
during better weather.
Plant Photoperiods
The most definitive characteristic of lightdeprivation
cultivation is the artificial
simulation of equal 12-hour light/dark
photoperiods. Using light deprivation,
cultivators seek to mimic the photoperiods
of the late summer and early fall, which
trigger plants to produce flowers. This idea
of artificially induced flower periods represents
a merging of outdoor and indoor
growing methods. While indoor growers
have timers that simulate night and day
in a growroom, light deprivation growers
must devise other means to black out the
sunlight during the 12-hour dark period.
It should be noted, however, that artificial
light deprivation methods are only
necessary in evening and morning in most
areas. Exposing your plants to sunsets,
moon rises, and the fresh air of summer
nights will generally improve their quality.
With that said, light deprivation enthusiasts
must devise blackout systems that
cover the entire canopy and exterior of
their gardens to block all sunlight in the
simulation of nighttime conditions.
Frames, Hoop-houses,
and Greenhouses
No matter how sophisticated or simple
cultivators wish to make their operations,
all light deprivation crops require an
exterior frame that supports a blackout
system. There are three routes one can
take in the creation of a framework: wood
frames, hoop-houses, and greenhouses.
Gardeners can create wood frames by
placing heavy wooden posts in cement
at the ends of the garden. These wooden
posts have heavy cables that support
the tarp and allow for it to easily slide
over the canopy of the garden. Secondly,
PVC hoop-houses can be constructed by
pounding two-foot pieces of rebar into the
ground at opposite
ends of the garden and
simply bending the PVC
over the canopy and onto
the rebar, forming a “hoop.”
Finally, greenhouse kits and
frames make excellent support
over which to pull blackout tarps.
Greenhouses provide growers with
the ability to utilize more environmental
controls than with wood frames and
hoop-houses, and greenhouses have
opaque walls as well as door systems,
making them more attractive for
privacy and security.
Tarp Systems
The sort of tarp-pulling system one
chooses for a light deprivation operation
will prove to be important for the
duration of a flowering cycle. This is
because the tarp has to be pulled over
the entire canopy of the garden twice
a day for an entire 55- to 70-day flower
cycle. Therefore, light deprivation cultivators
have to be present twice a day,
for two months solid, to ensure this task
is complete. In the novice operation, as
seen with wooden frames and hoophouses,
it’s often possible to simply pull
the tarp over the frame by hand or with
the help of ropes. To aid in this process,
growers also devise pulley systems
mounted on trees and wooden poles to
help with getting a tarp over a large or
tall frame system.
Finally, greenhouse companies have
designed a number of automated, less
labour-intensive systems that black
out daylight. These automated systems
include motorized tarp pulley systems
as well as large blinds that fold over
on one another to create a completely
dark environment.
Airflow During the
“Night” Period
Regardless of the scope of a light deprivation
operation, all cultivators need to
consider airflow in their gardens when
the tarp is pulled over the canopy during
nighttime simulation. This is because
the tarp hinders all airflow from outside
the canopy, presenting challenges with
humidity and subsequent issues with
mould and mildew. To remedy these
concerns, growers must employ intake
and outtake fans similar to those found
in indoor growrooms to ensure a steady
exchange of air when the coverings are
drawn. When choosing the size of inline
fans for intakes and outtakes, gardeners
should use similar considerations as
seen with indoor growing. Exhaust fans
“ THERE ARE THREE
ROUTES ONE CAN TAKE
IN THE CREATION OF A
FRAMEWORK: WOOD
FRAMES, HOOP-
HOUSES, AND
GREENHOUSES.
should completely exchange
the air in a light deprivation
garden in five minutes or less.
Depending on the size and the
structure of a garden, intakes
and outtakes can be mounted
on the framing system or simply
placed on the ground. However, for
air to move efficiently, it’s essential
that the ducting connected to these
fans is long enough so that the ends are
not covered by the tarp when it is pulled
over the frame.
Light deprivation greenhouses essentially
signal plants that seasons are
changing earlier than they actually are,
so growers can manipulate their crops to
produce more robust and frequent crops.
Keep in mind that some plants react
better to light deprivation methods than
others, and that issues such as excessive
heat or humidity, lack of oxygen to
the roots, and pest infestations can be
prohibitive. Once dialed in, however,
light deprivation technology can be used
to harvest early and often, particularly in
late summer and early fall.
Kent Gruetzmacher is a Californiabased
writer and the west coast director
of business development at Mac &
Fulton Executive Search and Consulting,
an employment recruiting firm. He is
interested in utilizing his Master of Arts
in humanities to explore the cultural and
business facets of this emerging industry
by way of his entrepreneurial projects.
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