Maximum Yield Cannabis USA February/March 2018 | Page 77

T
he Earth takes about 365.26 days—that is, one
year—to complete one orbit around the sun. The
axis on which the Earth spins is at an angle of 23.5
degrees relative to the sun. Due to this tilt, the two
hemispheres will, depending on the time of year,
have either a longer-than-average or shorter-than-
average exposure to the sun per day. This difference
in sunlight results in the seasons. When the
northern hemisphere is pointed closer the sun, the
southern hemisphere is pointed further away (and
vice versa). As such, the dates for the equinoxes and
solstices are reversed in relation to each other. They
do not always happen on the exact same date every
year due to leap year adjustments. 
The reason all of this is important to cannabis
gardens is because cannabis uses a process known
as photoperiodism to determine when to flower.
Specifically, flowering in cannabis is triggered by
long daily dark periods. This makes cannabis a
short-day (or long-night) plant. Artificially lit gardens
take advantage of this by denying the plants long
dark periods to keep them growing until they have
reached the desired size. Limiting the dark period to
six hours or less is a common method, although any
schedule that avoids a long continuous dark period
should prevent flowering.  
Light schedules intended to induce growth simulate
the light around the time of the summer solstice.
Summer occurs in the hemisphere that it is tilted
toward the sun, resulting in longer days, shorter
nights, and generally warmer weather. The summer
solstice, also known as midsummer, is the longest
day of the year. It occurs near June 21 in the northern
hemisphere and near December 21 in the southern
hemisphere. The months around the summer solstice
are the only months that do not have long enough
nights to trigger flowering in cannabis. However, if
flowering during these months is desired, outdoor
plants can be covered with opaque sheeting to
lengthen the dark period. This allows for flowering to
start earlier than it would naturally.  
Fall is a time of transition. The days continue to
get shorter and the nights longer until they are the
same length at the autumnal equinox. The equinox
occurs when the Earth’s tilt points perpendicular to
the sun, removing the preference of one hemisphere
over the other. The autumnal equinox is near
September 22 in the north and March 20 in the
south. Light schedules intended to induce flowering
simulate the light around the time of the autumnal
equinox, with 12 hours of light and 12 of dark. 
myhydrolife.com
“LIGHT SCHEDULES
intended to induce growth
simulate the light around the
time of the summer solstice.”
grow. heal. learn. enjoy.
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