Control red to far-red light ratio to limit stretching

lowerarchy · Dec 23, 2010

Just gotta interject here, fascinating thread. Thanks spurr and all you other contributors.

Quick thought - if you want a DIF of zero, could you simply heat your room to daytime temps all night? Sorry if this seems like a stupid question but it's so simple I don't see why everyone doesn't do it.

BlueberryLovr · Dec 23, 2010

Or cool your daytime temps to be close to night temps. aka run the a/c.

hades · Dec 23, 2010

Sup homie,

Thank God I am not the only one who thinks that someone got some words mixed up in those quotes! I kept reading it over and over, and thinking that they are mixed up, but they can't be wrong, right? LOL, webmasters aren't exactly the people who do the research, though....

What they describe is the red plastic mulch will trick the plant into thinking that other plants ARE crowding it, even though they aren't, and this will 'trick' them into 'competition' mode. They describe it as a reaction to surrounding plants reflecting the red into their canopy, and thereby increasing red:far red.

I guess what they are describing is a different response to increasing the red:far red. Either:
A) The plant thinks that it is being crowded from the increased red that is reflected off of nearby plants, and thereby goes into 'competition' mode.
B) The plant thinks it is alone by itself because more red is getting through its canopy than if it were being shaded by surrounding plants, and thereby does NOT go into 'competition' mode.

Strange..... I have to be missing something here....

3rdEye · Dec 23, 2010

lowerarchy said:
Just gotta interject here, fascinating thread. Thanks spurr and all you other contributors.

Quick thought - if you want a DIF of zero, could you simply heat your room to daytime temps all night? Sorry if this seems like a stupid question but it's so simple I don't see why everyone doesn't do it.

That's essentially what i have been doing lowerarchy

and it appears to work reasonably well. I have to collect more results before drawing more definite conclusions though.

spurr · Dec 24, 2010

lowerarchy said:
Just gotta interject here, fascinating thread. Thanks spurr and all you other contributors.

Quick thought - if you want a DIF of zero, could you simply heat your room to daytime temps all night?

Yup, that was the original way to make a zero or negative DIF, until ti was found the using DUMP works as well and saves on electric bills.

One point about using zero, and more so, strongly negative DIF (either as DUMP or not), is long term usage can negatively effect the plant, ex. can cause leaf chlorosis, slowed growth, etc. This is more of a worry when using strongly negative DIF (ex. lower than -10'F) for extended time periods, though. I have used zero DIF (via heating at night) for all of veg and pre-flowering without any issues, YMMV.

lowerarchy said:
Sorry if this seems like a stupid question but it's so simple I don't see why everyone doesn't do it.

Not at all, you question was a good one and will probably help people because using zero DUMP is not as easy as just using zero DIF. I see 3rdEye is doing what you asked about, as have I before too, so you are not asking a stupid question

spurr · Dec 24, 2010

BlueberryLovr said:
Or cool your daytime temps to be close to night temps. aka run the a/c.

The only reason that is not as good as increasing night temp is because we want to keep the ADT (Average Daily Temperature) above 70'F. It's the ADT that greatly affects growth rate, higher ADT (above 69'F) means faster growth.

Also, for most cannabis we grow highest rate of photosynthesis normally occurs at ~78'F; a bit higher at 80-86'F if using Co2 and high irradiance.

I found one study looking at effect of temp on THC production during veg stage, and it so happens the researchers used a zero DIF. And from the abstract we can calculate the ADT. Granted the study was flawed because they didn't use high irradiance that provides highest rate of photosynthesis for cannabis, and they didn't use Co2, and they didn't look at THC in flowering cannabis, and they used night temp that was too low, etc. That said, the study is still neat and worth something I think; I have yet to read it in full text, I referenced it below. I have other studies looking at day temp effects upon THC, I will post them later.

In the study below, the workers found when day temp (16h) and night temp (8h) was 25'C (~75'F), i.e. a DIF of zero and ADT of ~75'F, THC production was 30 times greater than THC production when day temp (16h) was 22'C (~72'F) and night temp (8h) was 12'C (~54'F), i.e. a DIF of +18'F and ADT of ~66'F.

The neat part about that study is it found a zero DIF and high ADT is positively correlated to higher THC, granted it was verses a night temp that was too low (i.e. ~54'F), so the results are not very valid; but still neat and worth considering I think. I hope when I get the full text the workers wrote about growth effects from zero DIF and 75'F ADT

"The constituents of Cannabis sativa pollen"
M. Paris, F. Boucher and L. Cosson
Economic Botany, (1975) Volume 29, Number 3, 245-253

spurr · Dec 24, 2010

hades said:
Sup homie,

Thank God I am not the only one who thinks that someone got some words mixed up in those quotes! I kept reading it over and over, and thinking that they are mixed up, but they can't be wrong, right? LOL, webmasters aren't exactly the people who do the research, though....

I am not sure, but I think they didn't make a typo, I think they meant fr:r and not r:fr because they did write about "tricking" the plant to growth more (i.e. stretch). We could email the relevant PSU dept. and ask for clarification.

hades said:
What they describe is the red plastic mulch will trick the plant into thinking that other plants ARE crowding it, even though they aren't, and this will 'trick' them into 'competition' mode.

I wish they would have not been ambiguous about it. If red light is reflected upward that would increase the r:fr ratio, and decrease the fr:r ratio; both of which we want as a means to reduce stretch. But if far-red light is reflected upward that would decreased the r:fr ratio and increase the fr:r ratio; both of which we do not want.

hades said:
They describe it as a reaction to surrounding plants reflecting the red into their canopy, and thereby increasing red:far red.

That is what we want, but they seem to be claiming two different things.

hades said:
I guess what they are describing is a different response to increasing the red:far red. Either:
A) The plant thinks that it is being crowded from the increased red that is reflected off of nearby plants, and thereby goes into 'competition' mode.
B) The plant thinks it is alone by itself because more red is getting through its canopy than if it were being shaded by surrounding plants, and thereby does NOT go into 'competition' mode.

Strange..... I have to be missing something here....

You and I both! From above, it would "B)", not "A)", because increasing the r:far ratio intraconapoy reduces stretching, i.e. not 'competition mode'.

:tiphat:

spurr · Dec 24, 2010

3rdEye said:
ust gotta interject here, fascinating thread. Thanks spurr and all you other contributors.

Quick thought - if you want a DIF of zero, could you simply heat your room to daytime temps all night? Sorry if this seems like a stupid question but it's so simple I don't see why everyone doesn't do it.

Click to expand...

That's essentially what i have been doing lowerarchy and it appears to work reasonably well. I have to collect more results before drawing more definite conclusions though.

Cool! Keep us updated on what you think

Microbeman · Dec 24, 2010

Dave Coulier said:
Gloryoskie, if you try to follow the steps outlined by Spurr you can get some incredible compact plants even on 18/6. Ive picked up plenty of things from him for awhile now, and do my best to incorporate them, and its paid off.

I keep my canopy temperature at 78-81 degrees, limit my DIF to +10 or less, and keep my ADT above 70 at all times. I haven't gotten a chance to incorporate the cold morning dump yet, but Im sure it'll have an affect just like he says.

Light source is a 6 bulb T5HO fixture running all G.E. Starcoat 54w 6500k bulbs.

Oh, and dont over crowd your plants.

Below is a picture of a 23 day old seed plant from Cannacopias Lemon Grass Thai x Deep Chunk. This plant was 5 inches tall before I removed its 7th node.

I hope I dont sound like that I am showing off a plant, but these pics are proof that Spurr's advise is sound, and will help you grow amazing plants.

I'm sorry if I'm dum or off base but is that plant not tiny for 23 days?

MrFista · Dec 24, 2010

LOL MM.

It looks ok, that's an arm in the first photo, the plant is short which was the plan. From seed it's good for 23 days seeds spend at least a week being pathetic.

Are you growing 21 day old trees and holding out on us with some guru gold?

Dave Coulier · Dec 24, 2010

Microbeman said:
I'm sorry if I'm dum or off base but is that plant not tiny for 23 days?

Tiny? No. Compact, yes. The fan leaves were as big as my hands at that point. Maybe your used to seeing foot tall plants at that stage that have 1 or 2 inch internodal distance. The ID on that plant was around half an inch.

3rdEye · Dec 24, 2010

spurr said:
Cool! Keep us updated on what you think

I will do my best to come back with some useful data and analysis... possibly even a conclusion or two some day. I'm encouraged by what i'm observing to date. Thanks again. So far this methodology is proving itself useful.
:cathug:

Very nice plant by the way Dave. Seems like temperature regulation along with r:fr ratios can complement each other well for helping steer ID lengths one direction or another. With sativas i would be inclined to keep plants as compact as possible, but with some indica/doms it might be better to have longer ID's for better airflow.

zenoonez · Dec 24, 2010

It is also a deep chunk cross so it probably vegs like a slug crawls in winter.

PrivateAero · Jan 2, 2011

would removing bottom and mid to lower branches make the plant not recognize the r/fr ratio or do they observe it from the shady side of the top leaves? just something I'm pondering.

Azeotrope · Jan 4, 2011

One way to see evidence of the R:B ratio effects is to veg and flower under a high wattage Philips 4k CMH (400w is their top) and then veg under 4k CMH and flower under the same wattage HPS.... If you do this with clones of the same plant the difference is night and day - all other variables being the same for each - I have been playing with this since 2002 and am now moving on to play with the GE 3k CMH as I am starting to think that it will have the ballance I want. With the Philips 4k the node spacing is so tight and leaves so large that a limited area like my cab ends up very crowded and there is a lot of "touching and shading" all the time.

Azeotrope · Jan 7, 2011

So, as I am truly amazed at the scientific level of study and understanding that several folks in this thread have regarding R:FR and R:B ratios.....Is there a solid or general guideline to follow when we start looking at Red, Far Red and Blue and appropriate ratios of each to the other???

Is it safe to say that due to environmental conditions and genetics of of an individual grow, everyone should shoot for a good or better understanding of what the effects of changing these ratios may/most likely would be and then work to find the ballance that best suits their application?

I mean I've been toying with every imaginable mix of HID in grows from 1800w down to
400w and have seen some really crazy effects on internodal spacing, yeild, quality and just weirdness!!!! I guess that is what I have been doing..... Using everything from ful spectrum CMH (4k & 3k), supplimental flouros to high kelvin halides and various assorted HPS bulbs (i hate HPS by the way). I think I've almost come home to roost now for my current small cab.

spurr - Is it just me or is the spectral information provided on HID bulbs only a very vague represention of what we get from those bulbs? I mean the graphs seem to follow a generall format not designed with horticulture in mind, but don't seem to tell us exactly what we get in terms of photons per nm ?

VerdantGreen · Feb 1, 2011

so far my red t5's that are supplementing the 250 hps seem to be speeding up the flowering response, which is logical from what i understand....

plants seemed to show sex quicker and bud up quicker too.

hard to say about stretch as im running unfamiliar genetics...

VG

spurr · Feb 4, 2011

Azeotrope said:
So, as I am truly amazed at the scientific level of study and understanding that several folks in this thread have regarding R:FR and R:B ratios.....Is there a solid or general guideline to follow when we start looking at Red, Far Red and Blue and appropriate ratios of each to the other???

No, not really. Just try for a little far-red, that is why an MH lamp is often better in terms of stretching, due to less far-red than many HPS lamps.

Azeotrope said:
Is it safe to say that due to environmental conditions and genetics of of an individual grow, everyone should shoot for a good or better understanding of what the effects of changing these ratios may/most likely would be and then work to find the ballance that best suits their application?

Yea that sounds pretty accurate. I think the easiest way to control stretch re R:Fr, is to use reflective walls and start flowering before the canopy is closed. Side lighting with red LED lights, or intracanopy, would also help quite a bit.

Azeotrope said:
I mean I've been toying with every imaginable mix of HID in grows from 1800w down to 400w and have seen some really crazy effects on internodal spacing, yeild, quality and just weirdness!!!! I guess that is what I have been doing..... Using everything from ful spectrum CMH (4k & 3k), supplimental flouros to high kelvin halides and various assorted HPS bulbs (i hate HPS by the way). I think I've almost come home to roost now for my current small cab.

Nice to see you experimenting

Azeotrope said:
spurr - Is it just me or is the spectral information provided on HID bulbs only a very vague represention of what we get from those bulbs? I mean the graphs seem to follow a generall format not designed with horticulture in mind, but don't seem to tell us exactly what we get in terms of photons per nm ?

That's true, every SPD I have seen for an HID lamp is on the basis of W/m^2 (e.g., a pyranometer); not on a microMole basis (i.e., umol/area/second). You can convert W/area into umol/area/second if you have the SPD, ex., knna's spreadsheet can do exactly that with reasonable accuracy. But even then, the value is limted because we often do no hang the lamp at the same distance used to make the SPD and we use different reflectors and ballasts and age of lamps, etc. If the SPD is made without a diffuse reflector than the SPD will be different (due to direct vs diffuse light) than the SPD we get when we put the lamp in a reflector with a diffusing insert.

The SPD is best used to get a rough idea of the radiance per nanometer (or at least nanometer range); so we can use the SPD to try and find a lamp with low far-red (i.e., ~720-740 nm). Ex., I just bought 1,000w Digilux MH and HPS lamps, both have very high radiance, the MH is higher than many HPS lamps; and both have low far-red. The MH has about considerably lower far-red than the HPS. If I used the MH for pre-flowering I would have reduced stretch vs the HPS, all things being equal.

UV-b range light help to reduce stretching of plants. That is another way a grower can affect the stretch, and increase THC and flavonoids (and maybe terpneoids) at the same time assuming sufficient UV-b irradiance is provided...

3rdEye · Mar 11, 2011

Just revisiting this thread. Due to a series of funny and fortunate circumstances i'm getting a new 1KW horti Super HPS.

I also have a 400W Eye Blue MH. Even though the Blue has much lower output I do hope to see some reduced stretching using this combination as opposed to the HPS by itself.

My idea is to start the day with the 400 for the first hour, then add on the 1K for the middle 10 hours, then finishing with the 400.

If luck permits then i will also be able to utilize 0 DIF strategies to examine stretch some more.

How's that sound?

inquest · Mar 14, 2011

Thanks for the great info Spurr! Right now I'm running a SE Asian microgrow and can use all the stretch reduction I can get!! I'm a bit limited in active temp control, but Ill document pertinent info as I progress.

Also, I'm open to suggestions, and you're all welcome to be part of my little experiment.

Control red to far-red light ratio to limit stretching

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