Hydrolife Magazine February/March 2017 (USA Edition)

ask kyle
Q
I’ve always thought using an 18/6 (18 hours on, six hours off) light schedule while plants
were in veg stage was the way to go, but recently I’ve been hearing a 6/2 (six hours on, two
hours off) schedule is better because pot plants only flower when exposed to long periods
of darkness. Is this true? Are there benefits or drawbacks to changing my light schedule?
a
abandoned using
I the traditional 18/6
schedule long ago due
to the following facts:
First, you can veg a
plant under 24 hours
of light, growing more
biomass in less time and getting you to
the point of flowering quicker. However,
after a few weeks, this benefit lessens
due to plants needing a break.
When the plants are photosynthesizing,
all the movements of water, nutrients,
and pressure go upward. At night,
the motor—so to speak—is turned off.
This allows for the pressure to reverse,
root exudates to be fully discharged,
and plants to rest.
Secondly, most of today’s strains are so
hybridized that they sometimes begin
flowering under an 18/6 photoperiod.
They require less darkness to begin to
flower. So, I adopted a 20/4 (20 hours on,
4 hours off) vegging schedule after two
to three weeks of continuous light. I find
this to be the best combination between
nature and production.
As with almost any subject regarding
cannabis cultivation, there are many
different schools of thought when suggesting
photoperiods. Are you most concerned
with maximum production and
yield? Is finding the most efficient input
of energy in return for yield what you’re
after? Does closely mimicking nature
make your heart sing? All the above are
valid intentions and widely practiced
throughout the home and commercial
agricultural communities.
I tend to fall into the category of those
trying to closely imitate nature whenever
possible. The second lighting schedule
you suggested above reminds me of
a cloudy day. The lights or sun come out
for six hours, then go behind the clouds
for two hours. I don’t see any gain by
denying your plants full sunny days. I’m
sure my vegetable garden grows bigger
when there are more sunny days.
However, there are noticeable gains to
be made regarding light intensity during
flowering. That’s the science behind the
new lights coming onto the market that
sequence short periods of lower wattage,
thus mimicking cloudier days and
giving plants a chance to recover from
direct, intense light.
Outdoors, in addition to clouds, the sun
moves across the sky, lighting different
parts of the plant. Indoors, the most intense
projection of your light hits the exact
same spot for the entire lit portion of
the photoperiod. This is one reason why
it is extremely important to have lots of
circulation, most importantly across the
space between your lights and plant
canopy. Plants should gently sway from
an intermittent breeze.
Late season sun is far less intense.
Having the same light intensity on
your buds at the end of the growing
cycle, as in the beginning, is less than
optimal. I always leave room for raising
the lights to double their distance
from the plant, or have the ability to
lower the wattage on digital lamps just
in case I don’t have the vertical space,
near the end. Growers may want to
consider 10-K finishing lamps, which
give off higher UV levels, mimicking
the late fall sun.
Kyle Kushman is an internationally renowned marijuana
cultivator whose collaborations have earned 13 Medical Cannabis
Cup awards, including three US Cannabis Cups for Best Flowers. As
the creator of Vegamatrix, the only line of vegan and organic nutrients
designed for growing cannabis, Kyle continues to make advances for
people who want to cultivate the purest, cleanest medicine possible.
Do you have a
question for Kyle?
Email editor@myhydrolife.com
to get an answer.
18
grow. heal. live. enjoy.
myhydrolife.com