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Photoperiod Peculiarity? Flowering Induced by 14 Hours of Daylight

Discussion in 'Growth' started by GanjaGardener, Jul 12, 2009.

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    After spending 8 weeks indoors under continuous (24/7) CFL light, my Shiva Skunk garden went outdoors, ostensibly, to continue vegetative growth under early May's 13½ -> 14hr daylight cycle. (Due to a miscommunication, the seeds for this grow were late in arriving. the start date got pushed back 6 weeks and the optimum timeframe for planting an early start/spring garden at my latitude had passed.) Instead of flowering under the 12½-13 daylight hours of April, my early start garden w/ a late start was still in it's vegetative state in mid-May and the days ahead weren't going to grow any shorter.

    I cleared out a room, light-proofed it and resigned myself to the task of moving an outdoors garden indoors for a 2-2½ hour dark period every evening for the next 2 mos to kick it into and keep it in it's flowering cycle. Well, a funny thing happened on the way to the Summer Solstice. My Shiva ladies began blooming in late May and they haven't missed a bud since.

    A corner of my garden. Plants have just entering their flowering cycle during a 14/10 photoperiod.


    10 days into flowering and the ladies are already dipping into my stash. shee-it! (Jun3)->


    Bud CU- a few days later (Jun7)->


    FF -> Present (Jul 10)->

    I train my outdoor plants horizontally to open them up
    to the maximum amount of light and to keep them low
    and out of the sight lines of any passer-byers.

    Octopus Angle


    Sideways Christmas Tree Angle


    Christmas Tree Angle






    CU Bud
    This shot was taken a week ago. Since then, some of the lower
    pistils have started browning up and the calyxes are getting frostier.
    I've harvested and dried some of the fluff bunnies from down under
    that were (conveniently) missed whilst I pruned and, uh, wait a second.....
    :smoking: ahh, mo betta........ now where was we ? oh yeah. ...
    the smoke tastes great and the buzz ain't half bad either.


    The flowering cycle for this grow kicked in during a 14 hour photoperiod, continued budding right through the Summer Solstice and is currently under trich watch. I know that a 12 hour photoperiod is the optimum lighting period for inducing an mj plant into blooming, (at my latitude), and I'm not here to make a case for a 14 hour mj work day. A 12/12 (or 11/13 southern) photoperiod induces flowering in nature and emulating nature is where it's at. What I'd really like to know is why the flowering cycle for this particular grow was induced by a 14+/10- hr photoperiod. If I can drill that down I, (you too, if interested), might be able to get close to re-creating the same cycle in future grows and w/ other cultivars. That begs a question, one that I will be asking you to weigh in on in a bit.

    Below are some of the thoughts or better yet, conjectures
    that I've been kicking around regarding the photoperiod and
    the flowering cycle of this grow. I have more questions than
    I have answers.

    1)In nature the plant's flowering cycle is triggered by the 12/12 pp (that conveniently lands on the fall equinox ;) ) and not by the 14/10 pp of May. But there's nothing in the plant's genes to prepare it for growing under 24/7 light for 2 months. The change from 0 hrs to10 hrs of darkness/da may have fooled around w/ the plant's genetic memory and tricked it into thinking that it's end had begun.

    2) I have a relatively unique outdoor situation. My garden is walled on 2 sides and abutted by buildings on the other sides. the plants receive direct sunlight for 8-9 hours/ da and bright shade prior to 9AM and after 6 PM. Taking away the vagaries of dawn and dusk, the photoperiod is a fairly absolute measurement (ie it's light or it's dark.) Still, I can't help but think that the quality of light may have some sort of effect on a plant's internal triggers. Long shadows and autumn harvests seem to go hand in hand.

    3) Shiva Skunk is described as an "easy to grow" (aka adaptable, flexible, forgiving), cultivar and as such, might be less demanding about the length of it's flowering pp than some of the other mj strains are. Maybe the 12/12 pp isn't as absolute as I thought it was. In any case, it's not as sacrosanct to me today as it was a couple of months ago when going into a darkroom w/ a flashlight that didn't have a green gel on it was a growing heresy that would most certainly cast my ladies back into a vegetative state.

    4) The plant's internal reproductive clock trumped it's photoperiod clock. Shiva Skunk is an early bloomer that, according to the breeders, flowers in 45-55 days. Although I'm happy with, make that *amazed* by the plant growth that is achieved under CFLs, (2300K, no less!), there's no doubt that the garden would've matured faster under a better indoor source. (ie hid's.) The upshot is that the plant's were moved outdoors on day 56, (1 day after, under normal circumstances, they were supposed to bloom) and the plant's reproductive hormones overrode it's photoperiod triggers.


    and one question~

    My intuition tells me that a flowering plant under 14 hours of light will produce better than the same plant would under 12 hours of light. My intuition also tells me that a flowering plant, (if you can get it to flower) will produce more bud and perhaps produce it faster under the light intensity level mid-July than it would under the mellower skies of early May or late Sept.

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    burndt out.

    High GanjaGardener :hello:

    I was reading this and I thought it might interest you:

    Marijuana Horticulture
    By Jorge Cervantes

    If the link doesn't bring you to the right page, it's page 173 Chapter Nine: Photoperiod
    It should answer some of your questions you have
    4 people like this.
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    Luke Highwalker Ultimate Gardener

    you gotta be careful when starting outdoor plants indoors...veg them at 15 hours a day so they wont flip when you set em outside.
    3 people like this.
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    something about cannabis sativa

    Cannabis Sativa
    Probably the most common form of Cannabis worldwide and also the type with the most applications. As a botanical name, sativa simply means ‘sown’ and is applied to the cultivated or common form of many agricultural crops.

    A typical Sativa is a tall plant, generally a lighter shade of green than the other types. Its leaves are made up of long, narrow blades. Female flowers are longer and more ‘feathery’ in appearance than those of an Indica.

    In general, the foliage of a Sativa is sparser than that of the other varieties Sativas grow taller than the other types, gaining height all through their growing and flowering phases. This is due to the equatorial origin of Sativas. In the tropical regions the length of day does not change very much between seasons, so Sativas are adapted to accomplish both their growing and flowering in a fairly uniform photoperiod.

    The female flowers of Sativa strains usually grow along the length of the stem and branches, instead of forming in clusters around the internodes, as with the other types. This flower formation is due to the Sativa tendency to grow and flower simultaneously. As a result, female Sativa flowers are usually less dense and weigh less than Indica flowers.
    A pure Sativa often requires a combined grow/flower period of around six months to ripen completely. For this reason there is no such thing as a pure indoor Sativa strain. All Sativa strains that are viable for indoor growing have been hybridised with Indica strains to make them more compact and faster to flower.

    Nearly all cannabis grown for industrial purposes is Sativa. As the tallest variety it produces the longest fibres and therefore has the widest range of industrial uses.

    Canna Zine comment;
    Sativa varieties bring with them a number of issues for the home grower and as the majority of sativa strains tend on the whole to be at the "stronger" end of the THC spectrum (the active compound, the bit that gets you stoned), this is what most of the fuss is about when it comes to the news headlines which announce "Cannabis 20x Stronger".

    If it were 20x stronger, it would most likely belong to the sativa family, but its not.

    The truth is, Sativa strains tend to originate from equatorial regions and as such, require far higher levels of light, and for longer periods, in order to produce the valuable and much-revered end product.

    I think it's genetics. Sativa's came from regions around the equator. They have adapted to an equinox year round.

    I believe it's in their genetics to be able to begin flowering fairly quickly as well as continue growth throughout their life. Hence the reason they get huge.

    I remember reading a grow journal about a guy growing a sativa strain in jamaica. He said that his crops start to flower with 16 hours of light and 8 hours darkness.
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    First off, great pics and great plants , GG!

    Saying that 12/12 triggers flowering is not accurate at all.

    What triggers flowering is a night period long enough once the plants are large enough so they has reached sexual maturity.

    The longer the nigh period, the stronger (faster) the flowering induction. Often is a long delay between the flowering signal and when the plant actually start to build buds.

    Although northen strains has adapted to longer critical night lenghts, most comercial strains have critical night lenghts below 10h. There are strain 9h critical drkelenghts. So 14/10 is for many strains (probably, for most strains) a flowering photoperiod.

    Although I induce the flowering under longer darkelenghs period, in order to get a faster flowering induction, once I see the first buds forming I flip my plants to 14/10, and do most of the blooming time under that.

    PS: Temperature affects the critical darklenght. When plants are indoor at higher nigh temps, critical darklenght is a little shorter.
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    Luke Highwalker Ultimate Gardener

    you flower 14 on 10 off? or the other way around?
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    Thanks for the feedback everyone. I would've gotten back to you sooner but I needed some time to process the info and do a little more research.

    I have a copy of Cervantes "Indoor Marijuana Horticulture" and the photo period info is pretty much the same in both books. But thanks for the cue. After carefully reading (and re-reading) the pp section, I found a couple of tidbits that I'd missed 1st time around.

    It also occurred to me that a book covering a subject that's as broad in scope as mj horticulture can't go into every mj strain in every growing situation. Handbook writers like Cervantes don't have the space to go into a subject like the pp in any detail and are relegated to playing it safe by making generalizations that apply to the "*majority* of indica plants (for instance) in *most* situations". The authors may feel that this is implicitly understood by the reader, but when I run across statements like, "Flowering is most efficiently induced in most varieties with 12 hours of uninterrupted darkness in a 24 hour photoperiod.", or "Marijuana must have 12 hours of uninterrupted, total darkness to flower prorperly." (both from Cervantes section on the photoperiod), it's easy to see why I assumed that the 12/12 photoperiod was the gold standard for initiating and maintaining the flowering cycle.

    I'm sure there are others, but knna is the first grower that I've met here that uses a 14/10 pp for his flowering cycle. 12/12 and flowering have almost become synonymous in books and forum discussions on the subject, (at least the ones I've visited.) -> How do you count days of flower

    I agree. Have never grown under 24/7 light before- was trying to compensate for a late start but I do know better. I ended up w/ a good (4:1 female to male) ratio but I think I got lucky this time around.
    16-18 hours is the maximum period of usable light for mj plants or "the point of diminishing returns" as Cervantes puts it. Just curious about how you landed on 15 hrs.

    I'm not sure if you're talking to me or to knna, but speaking for myself, (and I think knna too), 14 on and 10 off. I've read where some growers use 10 on and 14 off to kick in flowering for a couple of weeks before moving them to 12 or 14.

    gotta love that user name! although Shiva Skunk's genetics are primarily Afghani and indica in origin, (Skunk #1 x Northern Lights #5), the cultivar does have some sativa from Mexican, Columbian and possibly other So American parentage mixed in. The citrus element of the bouquet, that didn't show up until midway through the flowering cycle, is definitely sativa.
    Thanks for weighing in knna. We've discussed LED/lighting in the past, I respect your expertise and attention to detail and I think you hit the nail on the head w/ this one. As logical as your breakdown is, a 14/10 pp for flowering is still a minority view. My grow has been flowering for 7 weeks under 10-9½ hr darkperiods (14-14½ days) so I'm not about to argue w/ your conclusions.

    There's also a logical argument for a 12/12 cycle in plants w/ an Afghanica genotype, for instance. They originated in a latitude that has a 12/12 fall equinox.

    I don't doubt you. This does beg a question, though. What strains and what were the latitudes of origin of the plants the breeder's used to knock 2 hours off the darkperiod. Somewhere w/ long days and short summers I presume. Or maybe the selective breeding of parents that were tolerant of shorter darkperiods? :goof:
    2 people like this.
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    Both ways, I think.

    There is already wild strains with longer critical darkelenght photoperiod, although most of them have at least a part of Rudelaris. And of course, there are strains insensitive to photoperiod (autoflower ones), where the Rudelaris part is dominant.

    Those wild genetics are very often very little productive and have little THC, so breeders works with them in order to get strains adapted to north latitudes but being more productive and psicoactive.

    Luke, yep, 14/10 is 14 on and 10h off.

    I adviced many people to use this pp at least during the flowering peak, at the mid of the bloom stage, and for the moment none has reported me any revegging due it, nor I noticed it.

    Indica dominants hybrids works way better with these long photoperiods, while some sativa dominant hybrids likes them less: tend to reflowerings and the bloom takes longer, producing more sparsed buds. In general, sativas dom likes shorter photoperiods at higher light intensities, and there are strains that get better results using 10/14 and 11/13 than with the typical 12/12.

    12/12 is a good compromise for almost all strains, and due that its adviced to starting growers. But experienced growers with selected strains should study them to find what pp, or combinations of them works better for each strain. Some strains, specially sativas, grows better with shorter daylenghts, while other, generally indicas dom, grows better using longer daylenghts.

    And this just for people wanting to use just "natural" 24h photoperiods. Schedules with different duration than 24h, either longer or shorter, can be used and are able to give better results than standard 24h ones.

    Manipulation through photoperiod is one of the techniques with lots of possibilities that are very little used by MJ growers. Once a grower has learned the basics, finding the best schedule for a given strain is an interesting practice that may improve results, as photoperiod not only affect flower/veg status, but much more, as phenotype expression, quality/resin production, distribution of weight between parts of the plants and so.
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    Makes sense. 12/12 is a general recommended schedule to flower the majority of marijuana plants. Sort of like recommended feeding schedules on nutrient bottles; they can be followed or tweeked to suit the grower.

    I agree, i feel genetics plays a big role in the flowering for sativa and indica. Sativa's originated along the equator and are accustomed to an equinox. Essentially, they receive 12 hours of light during their veg but at high intensity. That would make sense why growing indoors, one should give them less light than 12/12. I assume they can handle higher temperatures?

    Indica is from the north. Well the name was given by a scientist who happened to study this specie from india. Hence he named it indica. When it can grow, weather permitted, it's used to longer days, shorter nights. Come fall, it experiences an equinox putting it into flower. So indoors, growers should veg it for 18/6 and flower closer to 12/12...maybe 13/11.

    Environmental adaptation is truly amazing.

    I'm still lost over ruderalis. Ruderalis originated from Russia and its name means "ditchweed/grows along side the road". I know they are photoperiod insensitive and flower based on age. Here is where my confusion sets in. This is for you to answer knna. The original ruderalis begins flowering after 7 weeks of 'growth'. Online, we have autoflowering strains, actually the majority, that are ready to harvest 70 days after germination and begin flowering once they reach about 3 weeks old.

    I know autoflowering strains are crossed with indica and sativa genetics, but how did we get the ruderalis to start flowering in 21 days as opposed to 7 weeks originally?

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    Im not a breeder, and I just have a basic understanding of breeding principles, so I think a breeded may ask that question way better than me and going deeper.

    But breeding is mostly a job of observing different plants and what traits they express, as sensivity to photoperiod and the maturity needed to start flowering, select parentals that starts to flower later and cross them selectively until get that trait constantly expressed in the offspring.

    Many botanist believes that "drug" type cannabis strains, high on THC, was the result of human breeding since many thousands of years ago, that cross selectively plants with the higher psicoactive effect. That active selection was which caused the current division between strains high on CBD (hemp) and strains high on THC (marihuana).

    Hemp has been cultivated and used for Humankind for so long for different applications that is difficult to say what traits are "natural" and what traits are selected, so sometimes deducing the caracteristics of a given strain just knowing its geografical origins may be misleading. As with maize, human activity is already fixed in the genomic of the plant.
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