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Interesting theory, use 50% less light in the last 3 weeks

ChaosCatalunya

ChaosCatalunya

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Talking to a friend recently about some information he has been given by a very busy, experienced grower who really knows what he is doing ..... so, slight Chinese Whispers but this is my take on it......

Basically he says that "You should cut 50% of your lights for roughly the last 3 weeks of harvest"

The theory is simple, in Nature, Autumn is a time of decreasing light, plants are used to this ...... with approx 3 weeks of the cycle left to go the buds have formed all the calyxes they are going to, defining your yield, so by reducing the light you are not reducing your yield. Added to this, excess heat is not good for buds, especially near harvest time, if anything you can/will loose flavour and possibly potency and may speed up any rot or mould problems, certainly Spider Mites, so it is win-win.

I have just put this theory to the test in a friends room [that really suffered from the heat this summer] and must say I am really happy with the result, very frosty, tasty, potent examples of cuttings I know well & have already grown myself elsewhere. IMO, seat of the pants opinion, the theory is good, and I do not think he lost any weight, just a 18% lower electric bill.

I had not heard of this or seen it discussed on IC or anywhere else, so I thouht I would share my mad theories and would love to know what others think.
 
J

JeffSpicoli

ive heard this is good to do with PURE sativas, but other than that i dont know....
 
ChaosCatalunya

ChaosCatalunya

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JeffSpicoli said:
ive heard this is good to do with PURE sativas, but other than that i dont know....
Click to expand...

Yes, now you mention it, I have seen that said here about Sativas ... but, as they are naturally Equitorial plants, they will be less seasonally affected [light cycle we know about, intensity less] than Indicas......so the effect should be more even noticeable in everything else other than pure Sativas ?


I am really talking about fine tuning 'normal' commercial Indicas/Hybrids used for cashcropping, not growing coinisseur Sativas for the love of it.
 
Pirate

Pirate

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Since you mentioned this being a "theory"............The only thing that jumped out at me is the fact the the sun is FAR more intense than our lights so even though it diminishes in the fall............its still far more intense than what we can create with HIDs. Just a thought.

So in order to reduce the light by 50% you would need the dimmable ballast right?
 
Last edited:
ChaosCatalunya

ChaosCatalunya

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Pirate said:
Since you mentioned this being a "theory"............The only thing that jumped out at me is the fact the the sun is FAR more intense than our lights so even though it diminishes in the fall............its still far more intense than what we can create with HIDs. Just a thought.

So in order to reduce the light by 50% you would need the dimmable ballast right?
Click to expand...

Yes it certainly is far brighter ... but ... in full sun, light it is not the most limiting factor for growth [plants onlly ever grow to the extent of the most limiting factor] ... and by Autumn I think some of my ladies get less outdoors than in ... in fact right now my Spring babies are in not out [in the day, [like normal] as it is a cold, gloomy day and my HPS sun is giving them more than the real one, wherever it is...

Reducing 50% can be achieved on one light systems with a dimmable digi ballast, with 2+, you just turn some off.

Matey also suggested raising the lights too, as he says the heat reduction is very important.


The results do look good, just by eye, the buds have filled out properly and are at least as aromatic and well developed as I have ever seen or done. I will try to get a pic of some Trainwreck bud up.
 
H

Haps

stone fool
Veteran
There is some truth to this idea, just enough to try. I did not see this as positive, although the right strain might work fine with it. My experiments were the last two weeks, three weeks is wrong in my opinion. I saw a reduction in bud volume and quality. That was my experience, and I can believe someone might get different results.
H
 
knna

knna

Member
I believe that changing photoperiods and light intensities along the flowering cycle is able to increase productivity. And for sure, this topic has been very little investigated on the MJ growing community.

But i think effect may vary depending on the strain, so you need to know what plants you are growing to take advantage of those techniques.

For example, talking strictly of this topic, reducing light on the 3 last weeks. Although leaves photosynthetic efficacy is reduced at the end of flowering, due to senescence and reduced N, and although at that point plants almost no grow anymore and only fatten bud slighty, all the vegetal matter built along this last stage is bud's tissue with strong tricomes density.

This mean that, although the weight gain vs light used at this last stage is low, its enterely "high quality" weight, which although may increase very little the weight of the whole harvests, most of the gain is added to resin weight. A 2% increase on fresh weight of the whole harvest is very little, right, but a 2% on the final resin yield may require a way larger increase on the initial (fresh) harvest weight.

I dont know if im explaining well my point, but it resumes in that added weight on the last stage is way more valuable than weight added previously, especially before the flowering peak about mid flowering.

So i really think that the opposite conclusion may be valid: use as more light as you can along the 2nd half of the flowering stage. It dont worth on g/w, but probably does if what we weight is resin/w.

On a grow with some differnt tables and lamps (not my case), it could be tested easily by reducing the light over one of the tables/areas, and compare results: fresh and dry weight, and finally, resin after an extraction).

I believe we could expect a noticiable change in the ratio of resin/weight from both tables.
 
ChaosCatalunya

ChaosCatalunya

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Haps said:
There is some truth to this idea, just enough to try. I did not see this as positive, although the right strain might work fine with it. My experiments were the last two weeks, three weeks is wrong in my opinion. I saw a reduction in bud volume and quality. That was my experience, and I can believe someone might get different results.
H
Click to expand...

Hi Haps,
Yes, an underrepeated truth on IC & elsewhere, so much, from start to finish, is down to the individual variety ....

2 weeks may well be better than 3, especially with shorter flowering plants.

Interesting you saw a reduction in volume and quality ... this garden was flowering different clones at a different time of year to last time round [when the heat really caused problems] so is not exactly a scientific experiment ... I intend to have a further play with this .... just on a seat-of-my-pants feel, I thought it was an excellent crop with great smell, taste, high and full calyx development.
 
ChaosCatalunya

ChaosCatalunya

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knna said:
I believe that changing photoperiods and light intensities along the flowering cycle is able to increase productivity. And for sure, this topic has been very little investigated on the MJ growing community.

But i think effect may vary depending on the strain, so you need to know what plants you are growing to take advantage of those techniques.

For example, talking strictly of this topic, reducing light on the 3 last weeks. Although leaves photosynthetic efficacy is reduced at the end of flowering, due to senescence and reduced N, and although at that point plants almost no grow anymore and only fatten bud slighty, all the vegetal matter built along this last stage is bud's tissue with strong tricomes density.

This mean that, although the weight gain vs light used at this last stage is low, its enterely "high quality" weight, which although may increase very little the weight of the whole harvests, most of the gain is added to resin weight. A 2% increase on fresh weight of the whole harvest is very little, right, but a 2% on the final resin yield may require a way larger increase on the initial (fresh) harvest weight.

I dont know if im explaining well my point, but it resumes in that added weight on the last stage is way more valuable than weight added previously, especially before the flowering peak about mid flowering.

So i really think that the opposite conclusion may be valid: use as more light as you can along the 2nd half of the flowering stage. It dont worth on g/w, but probably does if what we weight is resin/w.

On a grow with some differnt tables and lamps (not my case), it could be tested easily by reducing the light over one of the tables/areas, and compare results: fresh and dry weight, and finally, resin after an extraction).

I believe we could expect a noticiable change in the ratio of resin/weight from both tables.
Click to expand...

Hi Knna,

Again, yes, as haps pointed out, different strains will do all sorts of different things in different environments... we need to test things out to find out for ourselves, but there is a lot to be learned from shared experiences.

I have played with light cycles a bit, mainly reducing the 12/12 to 11/13 & 10/14 [10 on, 14 off ] to speed up late finishers, or so I thought.

I am fully with you on not skimping on the last few weeks and getting a plant to the max, I want the full weight, taste and potency... this was put to me as a way of getting just that, specifically that the plant does not need that much light, but is harmed in terms of smell, taste and potency, by higher temps in the last few weeks.

I dont think [but may well be wrong...] that the resin puts on any weight itself in the last few weeks, that comes from the calyxs swelling .. the resin just degrades, sagging, stalks going wonky, browning.
 
george j warner

george j warner

Member
you ay the sun is far brighter than our grow lights .... even when it hits the earth at 100,000 lumens ..... an air cooled 1k light produces 190,000 lumens at bulb .... and since its cooled it can get up close.

what the sun does have that we can never improve on, is intense canopy penatration
 
ChaosCatalunya

ChaosCatalunya

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george j warner said:
you ay the sun is far brighter than our grow lights .... even when it hits the earth at 100,000 lumens ..... an air cooled 1k light produces 190,000 lumens at bulb .... and since its cooled it can get up close.

what the sun does have that we can never improve on, is intense canopy penatration
Click to expand...

Pirate said it, but I am pretty certain he is right, that is what I remember ... 'the sun is far brighter than our grow lights'

I did not know the 100KL@earths surface figure, but lets take that ... even if you do use an air cooled, you will not be running it any closer than 18" [?, or you get no real growing area from it] where the 190KL has dropped to...? way less if I remember EdR's books right, possibly below the 100KL of the sun.

I always try to get my clones going strongly enough indoors to get them into flowering [ScroGs only these days] quickly enough so the canopy is not too thick to fill out the bottom buds anyway... in the recent experiment the crop was mildly lolipopped and there was nothing much under 0.7 grams at the bottom, regardless of the reduced light in the last 20 days.
 
JamieShoes

JamieShoes

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I'm glad I read this... I have 2 x 400w HPS and was planning to introduce the 2nd lamp toward the end of flowering...I may have to rethink that idea :)


In the case that you had 2 lamps and therefore the oppertunity to add or remove 50% of light easily, how would you "play" that?
 
DoobieDuck

DoobieDuck

Senior Member
ICMag Donor
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Chaos..I tried a little something in my last two grows for increasing resins. I cut from my 12/12 flowering cycle to 10/14 for a week, then to 8/16 for the last two weeks. The images are in my grow threads, Casey and Lapis. I can't tell you anything weight wise as I don't weigh a thing. But as a long time photographer I think it increases the visible resins. DD
 
mark1253

mark1253

Member
I have just read, copied and pasted this from another site (sea of green).....

Your ladies do not measure daylength only darkness.

When your about 2 weeks from harvest increase daylength to 24hrs on/12hrs off .


1.gives you about 15% more yield
2.use up any remaining nutrients in its system (organic growers)
3.improves taste dramatically for non-organic plants

Has anyone heard of this or even tried it ?
 
toohighmf

toohighmf

Well-known member
Veteran
I've heard going 13 on 11 off and raising your lights as well as adding UVB to the room the last 2-3 weeks depending on flowering times but it was a Big Mikes grow tip from Advanced nutrients... Can't beleive any thing that guy says after the lies he's told over the years..
 
P

purpledomgoddes

re-post... did the math below. there were threads on og/cw re this. also introducing colors of aurora borealis via party/led/flashlight+cellophane may influence plants. many ways to manipulate indoor enviromental variables.

16/12+12/16 stats fwiw
for what it is worth, in an 8 week (56 24hr periods) bloom cycle, the following are the differences w/ respect to the above:

standard 12/12
in 56 day/night 24hr periods:
7x24=168 total hrs per week
1x12=12hrs light per day
1x12=12hrs dark per day
7x12=84hrs light/dark per week
8x84=672hrs of light per 8 wk cycle
8x84=672hrs of dark per 8 wk cycle

16/12 cycle
6x(16/12)=168hrs per week
6x16=96hrs of light per 7 day calendar week
6x12=72hrs of dark per 7 day calendar week
96+72=168
8x96=768hrs of light per 8 week cycle
8x72=576hrs of dark per 8 week cycle

768-672=96 more hrs of light over an 8 wk period w/ 16/12
672-576=96 less hrs of dark over an 8 week period w/ 16/12

the standard 12 hr dark period is followed throughout w/ 16/12

12/16
how about 12 hrs of light w/ 16 hrs of dark? this will give:
6x12=72hrs of light per 168hr week
6x16=96hrs of dark per 168hr week

or

6x12x8=576hrs of light per 8 week bloom cycle
6x16x8=768hrs of dark per 8 week bloom cycle

768-672=96 more hours of dark per 8 week cycle w/ 12/16 than standard 12/12
768-576=192 more hours of dark than 16/12
 
knna

knna

Member
ChaosCatalunya said:
Hi Knna,

Again, yes, as haps pointed out, different strains will do all sorts of different things in different environments... we need to test things out to find out for ourselves, but there is a lot to be learned from shared experiences.

I have played with light cycles a bit, mainly reducing the 12/12 to 11/13 & 10/14 [10 on, 14 off ] to speed up late finishers, or so I thought.

I am fully with you on not skimping on the last few weeks and getting a plant to the max, I want the full weight, taste and potency... this was put to me as a way of getting just that, specifically that the plant does not need that much light, but is harmed in terms of smell, taste and potency, by higher temps in the last few weeks.

I dont think [but may well be wrong...] that the resin puts on any weight itself in the last few weeks, that comes from the calyxs swelling .. the resin just degrades, sagging, stalks going wonky, browning.
Click to expand...

Im not sure at all of the opposite either.

Ive just pointed out that eye conclusion for this topic, and still weight, may be misleading jugding results of this techs.

But i agree excess light intensity at the end of flower may enhance potency, but what ive noticed for sure is it degrades taste. So at least taste wise, reducing light intensity at the end of flowering works well. Just im not sold on the idea it worth if we are interested in potency or resin yield. I believe we will need to do accurate measurements to state that.

A tech ive been using on last grows is giving max intensity during peak flowering and during 1-2 weeks later, then keep intensity but reduce photoperiod (to 11/13 and 10/14). I tried to do it just for the last week, while raising sllighty the light, in order to force fast maduration, at the time of the finish flushing. But ive tried to strongly change this schedule, by reducing photoperiod some days before, but putting 16/8 for the last 3 (first try) and 6 days (last try), raising the lights.. There is no time for revegging, but im liking very much effect on taste, strongly enhanced IMHO (with all the subjetivity implied on taste reports).

Im trying to confirm if other growers have tried this and if they are getting same conclusion (on the other hand, ive noticed a slight loss in potency, but i prefer this taste for potency trade off hands down).

Resin yield wise, i think increasing light hours at the end while reducing light intensity worth. But its probable some strains, especially sativa dominant, dont react well to this treatment.
 
O

o0th3d4nk0o

I rememer my grandfather telling me before he passed away that he ran all his lights on 11/13 for flower all the way through.

but all of this makes sense
colder temps are good near the end to dense up the nugs a bit and get some colors showing.

I don't know about using less light per hour just less hours of light.!
 
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