i have always used 12/12, with the first number light on 2nd light off, now i am seeing 10/14??? i have grown white widow and was told to reduce light by 30mins per week in 12/12. my question is when and why do u guys change the 12/12 and to what effect? i was told on the widow to reduce the light to help in resign production? not sure... what about 2-3 days total dark at the end of flower???? L33t can u explain, only bin doing this for a year or so..
repo
Hi repoman,
To answer your question , well it mostly depends on the strain.There are many strains that will start to flower at around 8-9 of darkness.
Other strains need at least 11-12 hrs of darkness to start flowering properly.Usually equatorial sativas fall in this category.
So why/when do we prefer to use less hrs of light per day?
Well generally we want to use this type of light regime with sativas or sativa dominant plants that we want to force into flowering and make them produce lots of flowering hormones faster.Some sativas will flower for a long time and will not 'flower' properly but if we use less hrs of light per day we force the to flower and they finish faster.Indicas don't seem to have that problem and most will flower just fine even if we use more hrs of light (over 12).This has to do with evolution.In equatorial places light regime never goes over ~14hrs/day ('summer') and never drops below ~10hrs/day ('winter') so basically cannabis in that areas has been acclimatized over many generations to the natural environments light regime.Similar thing happens with plants that have been acclimatized in parts of the world away from the equator and closer to the poles of the earth (ie Canada, UK etc).In such areas the light regime is very different. The dark period is very long during winter but during summertime the dark period is very short. So a plant has been acclimatized there to start flowering with more hrs of light per day for its benefit.
Now when we flower plants indoors we sometimes want to force them to start flowering faster and want to make them finish faster.Using less over 12 hrs darkness/day does that.As I said usually sativas benefit from this and indicas don't.
A sativa/indica hybrid will most probably do fine with 12/12 light regime all the way during flowering but some sativas need to be forced into flowering with less hrs of light mainly for practical reasons.For example a sativa needs 18 weeks to finish under 12/12 and may take up to 8-9 weeks to show sex from the time that it is put in flowering mode , but if we use say 10light/14dark then it will most probabaly show sex way earlier and finish few weeks faster.Basically some sativas stay in a 'veg-flower' state if they are flowered under 12/12 so we need to force them to produce lots of flowering hormones in order to flower properly and faster.
As for gradually reducing the hrs of light per day during flowering as you draw closer to harvest time , this is like imitating nature again and it seems plants respond nicely (again I talk mainly about sativas).We can finish plants faster this way without the possible yield loss of a constant 'less hr/day' light regime throughout the whole flowering period.
The good thing with using sativas and less that 12 hrs of light/day is that the plants seem to focus on actual flower/bud production and not 'veg material' production which is always good.
Personally I 've tried to flower plants from seed with many different light regimes and I have experimented with quite a few strains . Ive tried to flower with 12/12 all the way, 11/13 all the way , 10/14 all the way even down to 8/16 all the way.I also tried the same things and lowered the hrs of light gradually.I 've tried things with pure sativas hybrids and pure indicas as well ..and got mixed results depending on actual method and strain.Gennerally I suggest dont start with less than 10/14 and dont finish with less than 8/16.Most sativas seem to like to flower with 11/13 and love the gradual lowering to as low as 8hrs light per day.
I am not sure about the effect on trichome production as I haven't done any side to side experiments but from the results I got from time to time I believe its good to lower the hrs gradually during the last weeks of flowering.As for the 3-4 total darkness period at the end of flowering before harvesting I can't say if it works but I like to leave the plants 36-48hrs in total darkness before I chop.I think shanti had said in an old CW post that the plants with genetics from the White family do benefit a little from an extended dark period at the end of the flowering before the chop.
Hope this helps
l33t