Maximum Yield Cannabis USA October/November 2018 | Page 76

Looking at flowering cannabis indoors, artificial light wavelengths seek to
mirror those occurring with sunlight in the late summer and fall months. Light
spectrums during these seasons see a significant shift towards red colors. In the
past, HPS lights have been far-and-away the most popular choice for cannabis
flowering. High pressure sodium lights, in both double-ended and single-ended
fixtures, are revered by cannabis growers due to their high-powered discharge
and wavelengths imbued heavily with red spectrums. It’s also worth noting
HPS lights can be utilized for vegetative growth — many hobbyist growers dual
purpose them for simplicity’s sake. Lastly, LED lights are gaining leaps and bounds
with cannabis flowering applications, as increasingly efficient technological
innovations are making the lights powerful enough to stimulate flower growth.
Concerning light spectrum analysis, LEDs essentially reduce wasted wavelengths
and focus specifically on the blues and reds with which cannabis plants respond
favorably. This cutting-edge approach ensures LEDs operate efficiently, greatly
reducing excess heat in growrooms as well as utility expenses for growers.
Plant Growth
Cannabis plants grow rapidly under the right environmental conditions, so how
you design your lighting schematic should account for this increase in canopy
size. Indica and sativa plants present drastically different growth patterns,
with indicas generally growing short and bushy and sativas stretching out to
extensive heights. This notion is exemplified when cannabis plants change from
vegetative to flowering phase, where most plants double in size. Growers must
look far beyond the first glance of a growroom when planning their lighting,
as the canopy will look much different when plants are in full-flower phase —
this anticipatory planning is especially important regarding ceiling height. If
curious about the ideal distances of certain lights to a cannabis garden canopy,
here are some figures to consider:
• Air-cooled SE HPS/MH lights: 12-18 inches from canopy
• Fluorescent lights: 6 inches from canopy
• DE HPS lights: 3-5 feet from canopy
• LED Lights: 18 inches from canopy
“When balanced correctly, grow lights are used
to trigger vital lifecycle changes in cannabis
plants as well as stimulate exceptional growth.”
Finally, growers should consider the space they need to work within their indoor
garden as relating to light fixtures, as massive hoods crammed into a small room can
easily render pathways impassible without a hard hat. As most experienced indoor
gardeners know, hitting your head on the corner of a hood is never a fun experience.
A good method for planning growroom lighting relating to anticipated plant growth
is to visualize a garden space with a specific strain of cannabis in mind. Let’s say
our hypothetical garden features eight-foot ceilings and the cultivator is planning on
growing a sativa-dominant strain like Blue Dream. The grower is unsure of their best
lighting choice and needs some more information to help them make a sound deci-
sion. It is not unusual for Blue Dream plants, even grown in smaller five-gallon pots,
to reach a height of six feet in full flower. Therefore, in this hypothetical scenario,
DE HPS lights are not an option as they run extremely hot and can easily burn foliage
if set too close to the canopy (they need three to five feet minimum distance). At this
point, this grower has two choices for their room concerning their lighting options.
They can implement air-cooled SE HPS lights or LED lights, which can both be utilized
in closer conjunction to a given canopy (they need 12-18 inches minimum distance).
Otherwise, this grower could choose to grow a stalky, indica-dominant strain like
Grand Daddy Purple and implement DE HPS lights.
Cannabis loves light and indoor growers seek to mimic the environmental
conditions in which this species thrives. When balanced correctly, grow lights
are used to trigger vital lifecycle changes in cannabis plants as well as stimulate
exceptional growth. When planning the lighting design of an indoor garden, these
plant processes should garner as much attention as infrastructure and cost.
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