Maximum Yield Cannabis USA October/November 2018 | Page 75
Secondly, cannabis is classified as a short-
day photoperiodic plant species, meaning
changes in sunlight patterns directly
dictate the seminal phases of a plant’s
lifespan. As most cultivators know, the
defining photoperiodic characteristic of
cannabis occurs with vegetative and flow-
ering cycles, in which 12 hours of uninter-
rupted darkness causes a plant to flower.
These light durations are indicative of
late summer and fall sun cycles. Serious
indoor gardeners must accommodate for
the biological demands of cannabis and
the plant’s accompanying changes in
growth patterns related to lighting.
In designing a lighting schematic for an
indoor cannabis garden, growers must
consider the advantages and drawbacks of
a variety of technologies — making deci-
sions between these can be difficult and
often boils down to subjective preference.
The primary grow lights on the market
today are: fluorescent, metal halide (MH),
single-ended high pressure sodium (SE
HPS), double-ended high pressure sodium
(DE HPS), and light emitting diodes (LEDs).
Rather than focus solely on growroom infra-
structure or the technical specs of specific
lights, the following information is based on
biological needs and growth patterns of the
cannabis species relating to light sources.
Vegetative and Flowering Stages
W
hen planning any cannabis grow operation — indoor,
greenhouse, or outdoor — light is perhaps the most
important variable to consider. Designing a functional and
efficient lighting system in controlled environment agriculture
can prove challenging. When considering indoor gardening,
cultivators must weigh several important variables relating
to infrastructure, budgeting, and plant growth when choosing
the proper lighting plan for a successful cannabis grow.
Physiologically speaking, there are several reasons why
effective lighting is so important in growing cannabis. To
begin with, cannabis has evolved to thrive in arid, sunny
climates. Indoor growers are well advised to create envi-
ronments and lighting schematics that match the ecological
influences in which the DNA of cannabis responds favorably.
Looking at the lifecycles of the cannabis
species regarding photoperiodism, the
most important factor to note concerning
growroom lighting has to do with changing
light requirements of both vegetative and
flower growth. Each of the crucial periods
of growth has specific requirements for
lighting. These changing light patterns are
indicati ve of seasonal changes in sunlight
patterns, spectrums, and intensity.
In the northern hemisphere, the vegetative
growth period of cannabis plants occurs
naturally in the spring and early summer
months. Studies show that light wavelengths in this time
of year present predominant blue spectrums. Under the
influences of sunlight imbued with blue light wavelengths,
cannabis plants naturally grow stout and strong during
the vegetative photoperiod. As a result, grow lights
designed specifically for vegetative growth seek to mimic
the spectrums occurring naturally in the spring and early
summer months. Traditionally, fluorescents and metal halides
have been the grow lights of choice for vegetative indoor
cannabis cultivation because they present predominant
blue wavelengths. In recent years, LED lights have grown
in popularity as the relatively new technology is trusted by
growers to handle vegetative growth, which is not nearly as
demanding as seen with flower production.
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