photo-period and how it works! we all know the basics of vegging and blooming cannabis. when the day is long and the night is short the plant concentrates on vegging (growing), when the day length shortens enough, the plant starts to bloom. but how does all this work? why does the same strain finish at different times in different parts of the world? does 12/12 really mean anything outdoors? why is latitude(or "lat") so important to some growers? what is a "auto-flowering" plant? lets get into the meat of the subject shall we? photo-period the first thing to cover here is photo-period- photo-period is the amount of time there is light in a 24 hour period. in cannabis growing, photo-period is typically shown like this- 12/12 or 16/8, or 18/6, etc. the first number is usually the length of the lighted period, the second shows the balance of the 24 hours that is dark. outdoors the sun controls the photo-period. its length changes through the seasons according to the movements of the sun in the sky, a matter of fact it causes the change in seasons. this brings us to...... photoperiodism photoperiodism is the reaction of many flowering plants (including cannabis) to changes in photo-period. plants that experience photoperiodism have pigment cells called phytochrome that monitor the amounts of light being absorbed by the plants (specifically the red end of the spectrum), and the length of day. signals from the phytochrome tell the plant to do many things, including to grow, bloom, and in the case of some trees, to loose their leaves and go dormant in autumn. most of these plants fall into three categories concerning blooming times, that being- long day plants(blooms as day gets longer), short day plants (blooms as day gets shorter), and day neutral plants(blooming is not according to light cycles). all cannabis varieties are either "short day", plants or "auto-flowering" (known as "day neutral" outside of the cannabis community). so called "auto-flowering" plants do not seem to take their blooming cues from the sun, and thus should be considered "day neutral", as most seem to be genetically programmed to bloom according to age instead. the year as we know it is basically the time it takes for the earth to make a complete loop around the sun. as the earth makes this loop it shifts on its axis, so that either the northern half or southern half (hemispheres) have the longer photo-period. the shortest day of the year is called the winter solstice, this day occurs on december 21st in the northern half of the world, on the same day in the southern hemisphere they will have their summer solstice, the longest day of the year. on june 21s it will be reversed, with the longest day of the year in the north (summer solstice), and the shortest day in the south (winter solstice). two days of the year are known as the equinoxes, one occurs march 21st and one on september 21st. these days represent the halfway point between the longest and shortest days of the year, on these days the day length is almost exactly 12/12 all over the world. if you are in the northern hemisphere, mar. 21 is the first day of spring and september is the first day of autumn, reverse these dates in the southern hemisphere. next i will go into talking about latitude. jw
Posted on: Mon, 22 Jul 2013 20:20:38 +0000
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