Drowning in conflicting plant graphs - help! (LED)

[bigsby]

We ain't growing orchids...

[demoreal]

Does different wavelengths of light create different results. If you have too much blue light during flowering would it create a leafy plant? Would you want more red? Possibly more blue during stretch then dim it a bit. More red then blue at the end. I don't know.

You guys are right. If I owned a LED with a dimmer I would most likely just crank both up during flowering. There are people that use MH for flower?
The point of the dimmer would be to use different wavelength ratios depending what stage of growth you are in. The same reason people use a different light for veg and then one for flower.
Has anyone done a side by side with an MH and HPS for flower? Does the MH create more leafy growth?
This would be a reason for a dimmer.
If this reason exists. I have no idea.
I have heard people claim to much LED during flowering is not good? (I do not know if I believe that) but if it is true it is another reason to crank up a more beneficial wavelength and mellow out another. Kind of like what you do with nutrients.
These are some reasons a dimmer would be nice. If these reasons even exist. There could be more???? Or maybe a dimmer is an unnecessary idea...

[RackitMan]

I live in the hottest & driest part of the country and am unable to properly cool and humidify my closet due to circumstance, which is why I got interested in LEDs. CFLs work fine for me lumen -wise, but the heat is way too much. So if I could minimize the watts used until I really need them, it would be a plus.

[mrnobody]

"I'm no director of research - far from it... but my limited understanding tells me that plants do not use the entire light spectrum"

Of course they do if they can! Hence the reason why outdoor grown green alwasy tastes better. Most plants, although I am not sure about cannabis, although the point about plants is made, most plants when the reach a point of cell saturation with light and they can absorb no more evolve and grow new cells capable of absorbing the light. What we forget is that its thanks to Afgan Week to do have what we do today if my somewhat limited knoweldge serves me correct. Weed will grow and adapt, evolve, learn and suit the environment its in. So if you saturate it with full spectrum light and supplement with high end red for flowering and blue for veg like we know works the plants with naturally be healthier as we are getting closer to nature. is that not what we should be striving for. Less mono-cultures and more diversity and through evolution.

They actually think plants in this world was once purplr or red because retinol was that active componenet not chlorophyl. Makes you think and makes you realise how plants evolve.

Stick them under Plasma, supplemental LED dialled in to your spec and watch the results. Better, stickier green. Closer to nature. Its this we need to be discussing and trying out.

[headshake]

I'm no director of research - far from it... but my limited understanding tells me that plants do not use the entire light spectrum. In fact, it uses quite limited amounts of white, yellow, orange and green. So an HPS that pumps out tons of "white" light (not to mention heat) is wildly inefficient. It is successful due to the high photon flux rate across the spectrum.

white, or visible light is composed of red, orange, yellow, blue, green indigo and violet light (or wavelengths). the part of the electromagnetic spectrum that we see is from about 390nm-750nm. plants use all the wavelengths except for green, which they reflect, hence why plants look green to us.

I've seen these lights LEDs with dimmers and I've wondered why you would use them. OK, with young seedlings you don't need to raise the light if you can dim it. And I guess you could tweek them to better mimic sprning / summer / fall lighting but really, the major factor is time phase (12/12 vs. 18/4) so once your seedlings are into veg wouldn't you just crank the LEDs all the way up and leave them there to maximize output / penetration?

the reason i suggested dimmers was because you would have independent control of all the wavelengths at your fingertips. you would be able to tweak the ratios of every wavelength (that are currently available).

i, also, by no means am an expert. just an avid reader with more questions.

i applaud all of you for pushing the envelope.


-shake

[headshake]

Has anyone done a side by side with an MH and HPS for flower? Does the MH create more leafy growth?

MH does promote more leafy growth, hence it's used for veg, and the red of an HPS mimics the fall (harvest) sun.

i have read a study, and although it doesn't relate to MH vs. HPS specifically, it is still interesting. two crops of MJ were grown, one at 4500ft elevation, the other at 9000ft. the crop at 4500ft had about 25% more yield, but the one at 9000ft had better trich production. i know this pertains more to UV than spectrum (although, UV is a spectrum, or a group of really). with that being said, blue light and light closer to the blue end of the spectrum is more powerful than light at the red end due to frequency (i believe).

good growing!


-shake

[bigsby]

My first sentence was not as well formed as it could have been although if you had read a bit more closely you would have seen my point. Try this:

I'm no director of research - far from it... but my limited understanding tells me that plants do not use the entire light spectrum equally. In fact, they use quite limited amounts of white, yellow, orange and green.

The point being that plants do not need the same levels of white, yellow, orange or green as they do red and blue. They use almost no green spectrum (our plants are green because they reflect this light back rather than absorb it). A grow that benefits from direct sun light tells us nothing about their ability to absorption white, yellow, orange or green spectrum. That's just misplaced causality.

Thanks headshake, I knew that about white light and it occurred that I should up pack that but you did it for me.

[khyberkitsune]

As you are the most knowledgable here, I have two more questions if I may.

1. I can find nothing in the science that suggests a 6 or 8 to 1 red/blue ratio. Is this just attempting to copy HPS/MH spectra or are there real studies that support this? On one advanced cannabis board (engineers not growers), the conclusions was a blue to red ratio of 1.5 to 1 is best, while the absorption graphs look like it should be closer to the inverse, but nothing as extreme as all of the popular LED lights.

2. As you stated, and I have come to the same theoretical conclusion, that it's the photosynthetic photon flux density that is most important.

Let's assume these mfg numbers are accurate for this discussion. If I have a white LED that outputs 100 lumens/watt and has a higher total PPFD than either a 75 lumen/watt red or blue LED, (sorry no spreadsheet) why would I not go with all white LEDs? The spectra is something roughly like 40% blue, 10% green, 20% yellow and 30% red. (Don't hold me to those numbers.)

Any light you can shed (no pun) on these topics would be greatly appreciated.

Thanks!

1. There is nothing to support the current red-dominant ratios being made, and in fact several other studies show that greater amounts of blue are needed for proper flowering and seed production and bulk fruiting. At best they emulate the light from an HPS (though they never hit the photon flux density the HPS outputs in the same peaks.) Most MH lamps will outperform typical LED panels with such crappy balance. As for which spectral peaks matter, that's a really, REALLY dependent question. It depends upon the plant species, sometimes varying wildly between individual strains. In most plants that are green/yellow in color, They'll tend to use the red and blue peaks, green and yellow tend to inhibit the growth process except for trace amounts. The plant is still absorbing *SOME* of that light, but the majority is reflected back to us. On the other hand, you take something like the 'Wandering Jew' or 'Creeping Jesus' plant, which is predominantly purple/blue in color, is typically found in shaded areas, so mostly green and yellow light filter through to it, and it takes maximum advantage of this. This plant will actually PREFER an abundance of green and yellow light, and unless one tailored an LED panel to accomodate for this, the best bet for this would be the HPS lamp.

Assuming the 100lux/w figure, I wouldn't go with the white LEDs mainly because they burn out faster than any other pure-color LED - phosphors are used to shift the light into other visible wavelengths. Added to that, again, depending upon the plant you're growing, some of that light will act as an inhibitor. Of course, given that particular type of LED doing such lux at such low green/yellow output, you'd be better off finding the single-color versions of that same bin diode and using that instead, as you'll be pumping maximum usable power to the plant that way. A lux figure won't usually help you, but if you've got that plus the output chart, you can figure out what's rolling from where, as you weigh the lux figure to the green wavelengths, and then you can see the relative higher outputs for the other usable colors. This is how I determined usability of non-LED growing lamps when no PPFD figures are available (Maybe two bulb makers on the entire plant for HID/Fluorescent actually include that figure.)

[demoreal]

Would it be beneficial to have a LED light with adjustable angle to play with the photon flux density?

[RackitMan]

There are adjustable lens from 4 to 90 degrees for the higher wattage LEDs. Not sure how much power is absorbed by the lens.