Dim LEDs near harvest ?

Prawn Connery

Prawn Connery

Well-Known Member
Well there you go. That sounds very reasonable. What strain is it?

If I could offer a suggestion, don't water it during the dark period and try to judge it so that by the third day, just prior to harvest, it is starting to droop from dehydration. The science behind stressors promoting cannabinoid production is that predators (mites and other insects) usually target the weakest plants first, so it is a front-line defense mechanism.
 
nfhiggs

nfhiggs

Well-Known Member
Prawn Connery said:
Well there you go. That sounds very reasonable. What strain is it?

If I could offer a suggestion, don't water it during the dark period and try to judge it so that by the third day, just prior to harvest, it is starting to droop from dehydration. The science behind stressors promoting cannabinoid production is that predators (mites and other insects) usually target the weakest plants first, so it is a front-line defense mechanism.
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I can't "not water it", its in a hydro Dutch Bucket. Like a Hempy bucket it can go several days without watering.

I started with Jack Herer and Plushberry. I've since lost track of what clone came from what plant. But I think this one is a Plushberry.
 
Enigma

Enigma

Well-Known Member
Prawn Connery said:
What you note is what I've seen with most 8-week strains - usually that Week 6 period is when they really swell. In the end, I simply stuck with HPS because I grew vertically and actively tried to promote stretch during the first two weeks so the rest of the plant would fill in from top to bottom. It is not the same as a horizontal grow where you want to keep stretch to a minimum and promote an even canopy.

If you have 3000K and 4000K boards, I guess what I'm saying is using all available light at all times (up to the point of heat/light stress) will - in my experience - produce better yields than using half your available light in the first couple of weeks.

Remember, those first two weeks of stretch grow the "bones" on which to hang the buds. That is also the most active time for root growth, which is key to supporting heavy flowering later in the cycle.

The caveat is that by harvest time you haven't overcrowded your grow space and you are not giving your plants more light than they need to the point of stress (a little extra light is better than not enough). If you feel that one board alone in the first two weeks is adequate to promote enough stem and root growth so that after adding the second board you are not sacrificing yield by the end of the grow, then I would try it.

Eventually, you will find what works best for your environment.

P.S. I've read good things about the Heri - Sannie's a decent guy.
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The spectral graph for the Vero29C in 4000K carries plenty of red light, I believe more than most MH lamps I've seen. One of these would produce around 700 PPF @ 70W in the space I have right now. That's more than enough to aggressively veg, then two 3000K would produce nearly 1400 PPF @ 70W each.

Running all three @ 70W would be over 2000 PPF, that's suicide.

I could underdrive the reds to half and achieve 1400 PPF with the blue.

From my HID days, red light stacked more weight and blue light made it tastier. What I want to know now, that LED has evolved past the blurple panels, is how well can I use these to my advantage.

On an eight-week strain, the first couple of weeks not a whole lot of bud production is going on, every plant I've seen acts more like it is in veg mode but it is climbing for the stars. The next four weeks I've noticed intense bud growth with "frost" forming about half-way through. Finally, the last couple of weeks I don't see much swell. What I do see are the trichs covering everything, even the sugar leaves.

That's what makes me think, blue has been known to enhance flavour and keep plants tight while red does a much better job of putting on weight, so why not take advantage of that knowledge to focus each stage of development with the most conducive light spectrum?
 
Prawn Connery

Prawn Connery

Well-Known Member
I can't strictly answer your LED questions, as I have no experience with them myself, but in theory I see nothing wrong with running the 4000k for the first two weeks - maybe even 1 x 4000 and 1 x 3000 - and then run both 3000s for the remainder. 4000K isn't really that blue (compared to MH bulbs in the 5000-6000k range), while 3000K isn't really that red (compared to most HPS bulbs,which are in the 2100-2700k range). You might want to just run the 3000/4000 combo the whole way through, or just for the first two and last two weeks . . . but I wouldn't cut my light in half for the last two weeks, as 8-week strains are still packing it on in the 7th week, and most will continue flowering significantly into the 8th.

You'll have a better idea of what suits your system, but my initial response would be to say you will compromise yield if you compromise light.

Now, it's not always about the yield - especially if you are a personal and/or med grower - so if you like the results of combining the two spectra, then that, in itself, is a success. Even if you do lose a bit of yield. I have also seen sativas respond well to slightly bluer light (MH/HPS combo) and indicas respond well to redder light (straight HPS). The extra induced stretch in the indicas can help with yields (spacing nodes to allow more light penetration through the canody) while preventing mould/bud rot, which can be a real problem with dense colas in cooler, more humid months, even with lots of direct ventilation. Sativas, on the other hand, can respond well to tightening the nodes - especially in a horizontal grow.

Heri has pretty dense buds on an open structure (for an indica) anyway, from what I've seen, so maybe a light combo would work?

Me? I'd be looking for an LED in the 2700k range for a pure flowering light, so I reckon 3000k is already a bit of a compromise. But you know, results speak for themselves, so I really don't know if there's direct comparison between 2700k of LED and 2700k of HPS - that would just be my starting point.
 
BobCajun

BobCajun

Well-Known Member
WeedSexWeightsShakes said:
I've been doing 10/14 from the start. With QBs I bet you could get away with 8/16 from the start?
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There's a person with a whole thread on his 8/16 flower cycle, Torontoke is his forum name. Seems to like it for some reason. It works, but it must reduce yield. No way 8 hours could equate with 12 hours light, but plants can still grow on it. Even down to 6 hours works, just with slower growth. I think around 5 is the bare minimum to keep a plant from dying.
 
P

Photon Flinger

Well-Known Member
BobCajun said:
There's a person with a whole thread on his 8/16 flower cycle, Torontoke is his forum name. Seems to like it for some reason. It works, but it must reduce yield. No way 8 hours could equate with 12 hours light, but plants can still grow on it. Even down to 6 hours works, just with slower growth. I think around 5 is the bare minimum to keep a plant from dying.
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Why? I am running 6/18 now and they are still getting 36 DLI. Works fine.
 
Enigma

Enigma

Well-Known Member
Prawn Connery said:
I can't strictly answer your LED questions, as I have no experience with them myself, but in theory I see nothing wrong with running the 4000k for the first two weeks - maybe even 1 x 4000 and 1 x 3000 - and then run both 3000s for the remainder. 4000K isn't really that blue (compared to MH bulbs in the 5000-6000k range), while 3000K isn't really that red (compared to most HPS bulbs,which are in the 2100-2700k range). You might want to just run the 3000/4000 combo the whole way through, or just for the first two and last two weeks . . . but I wouldn't cut my light in half for the last two weeks, as 8-week strains are still packing it on in the 7th week, and most will continue flowering significantly into the 8th.

You'll have a better idea of what suits your system, but my initial response would be to say you will compromise yield if you compromise light.

Now, it's not always about the yield - especially if you are a personal and/or med grower - so if you like the results of combining the two spectra, then that, in itself, is a success. Even if you do lose a bit of yield. I have also seen sativas respond well to slightly bluer light (MH/HPS combo) and indicas respond well to redder light (straight HPS). The extra induced stretch in the indicas can help with yields (spacing nodes to allow more light penetration through the canody) while preventing mould/bud rot, which can be a real problem with dense colas in cooler, more humid months, even with lots of direct ventilation. Sativas, on the other hand, can respond well to tightening the nodes - especially in a horizontal grow.

Heri has pretty dense buds on an open structure (for an indica) anyway, from what I've seen, so maybe a light combo would work?

Me? I'd be looking for an LED in the 2700k range for a pure flowering light, so I reckon 3000k is already a bit of a compromise. But you know, results speak for themselves, so I really don't know if there's direct comparison between 2700k of LED and 2700k of HPS - that would just be my starting point.
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Each manufacturer produces emitters with different outputs.

If you check the spectral graphs for the Vero29 you'll see the 4000K and 3000K to clearly be the strongest.

In fact, I don't believe I've seen a MH Robbie able to produce as much red as the 4000K does, with a massive spike in blue.

You'll have to research your emitters before you arbitrarily start choose colour temps.


BobCajun said:
There's a person with a whole thread on his 8/16 flower cycle, Torontoke is his forum name. Seems to like it for some reason. It works, but it must reduce yield. No way 8 hours could equate with 12 hours light, but plants can still grow on it. Even down to 6 hours works, just with slower growth. I think around 5 is the bare minimum to keep a plant from dying.
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I believe the experiment was a bust. I remember reading a thread about this before, he settled on 10 hours of light being the absolute minimum. Any less and you sacrifice weight.

It could have been a different person with the same experiment.
 
BobCajun

BobCajun

Well-Known Member
Enigma said:
Each manufacturer produces emitters with different outputs.

If you check the spectral graphs for the Vero29 you'll see the 4000K and 3000K to clearly be the strongest.

In fact, I don't believe I've seen a MH Robbie able to produce as much red as the 4000K does, with a massive spike in blue.

You'll have to research your emitters before you arbitrarily start choose colour temps.





I believe the experiment was a bust. I remember reading a thread about this before, he settled on 10 hours of light being the absolute minimum. Any less and you sacrifice weight.

It could have been a different person with the same experiment.
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Well considering that the day length never gets more than a few minutes shorter than 10 hours in Kabul Afghanistan, I doubt any Indica dominant strain would benefit from less. Probably acclimated to ripen by the time it gets down to 10.

On the red light, with LEDs you sacrifice light output to get more red, because it has to be produced from the blue LED causing the phosphor layer to fluoresce, and it's inefficient. You're actually better off getting a high cct, like 5000k or higher, and putting just a few lower cct ones in with them to supply enough red to activate the flowering response. You don't need a lot of red for that actually.

Does more red equate to better flowering? I doubt it. Why would it? It only takes a few watts /sq meter to trigger the phytochrome response. Pure blue light always produces more dry weight than pure red, or any other color in experiments, but some red with it produces more normal plant shape. With HPS it doesn't matter because the red is not produced by phosphors, so there's no efficiency hit.
 
P

Photon Flinger

Well-Known Member
BobCajun said:
Oh yeah, cool. Have you used that cycle for a full flowering yet or is it a new thing you're trying? If you used it before, how did it turn out?
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The test cycle is just finishing now so I can say it does work. Temps in line, good air flow and 1500-1850 PPFD at the canopy.

Next cycle will be 24 cobs/1m2 at 12w each.
 
Prawn Connery

Prawn Connery

Well-Known Member
Enigma said:
Each manufacturer produces emitters with different outputs.

If you check the spectral graphs for the Vero29 you'll see the 4000K and 3000K to clearly be the strongest.

In fact, I don't believe I've seen a MH Robbie able to produce as much red as the 4000K does, with a massive spike in blue.

You'll have to research your emitters before you arbitrarily start choose colour temps.
Click to expand...
I absolutely understand this. MH and HPS, for the most part, complement each other in terms of spectral output, which is why many old-skool growers combined them 2:1 to try to replicate a full spectrum HID.

While HPS produces most of its light in the photosynthetically efficient yellow/red spectrum, it also produces a fair amount of far red that, while promoting stem elongation (internode spacing), is also responsible for flowering. Plants will convert Photochrome Red (Pr) to Photochrome Far Red (Pfr) in the absence or shortage of far red light (which uses stored energy) to propagate flowering.

BobCajun said:
Well considering that the day length never gets more than a few minutes shorter than 10 hours in Kabul Afghanistan, I doubt any Indica dominant strain would benefit from less. Probably acclimated to ripen by the time it gets down to 10.

On the red light, with LEDs you sacrifice light output to get more red, because it has to be produced from the blue LED causing the phosphor layer to fluoresce, and it's inefficient. You're actually better off getting a high cct, like 5000k or higher, and putting just a few lower cct ones in with them to supply enough red to activate the flowering response. You don't need a lot of red for that actually.

Does more red equate to better flowering? I doubt it. Why would it? It only takes a few watts /sq meter to trigger the phytochrome response. Pure blue light always produces more dry weight than pure red, or any other color in experiments, but some red with it produces more normal plant shape. With HPS it doesn't matter because the red is not produced by phosphors, so there's no efficiency hit.
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I can't say I agree with the above. While I don't have any experience with LED growing (that's why I'm here - to learn), in the HID world, red always outyields blue in terms of flower output.

You probably already know that equatorial sativas are very sensitive to photoperiod, given the smaller changes in daylight hours, but some East Asian sativas grow much further north than Central Asian indias. For example, I've seen land-race sativas growing as far north as the 45th Parallel in northeast China (further northeast, you start getting into Ruderalis territory), and indicas growing north of the 40th Parallel in northwest China, north of the Hindu Kush.

My personal theory on the evolution of sativas/indicas has a lot to do with humidity being responsible for the taller, thinner, more open structure of sativas vs indicas, which tend to be confined to dryer, land-locked areas. That would account for why some landrace sativas grow further north in East Asia than Central Asian indicas, as China, Korea and eastern Russia are affected by the East Asian Monsoon, which translates to hot, humid summers, but freezing, wind-swept winters. Sativas are much more mould-resistant than indicas. But, of course, I'm going off on a tangent . . .
 
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