Light color and it's effect on plants?

[cynthia_h]

I found a Kelvin Temperature Chart jpg at

https://en.wikipedia.org/wiki/File:Kelvin_Temperature_Chart.jpg

which seems to show that red-spectrum temps run from approx. 1500 deg K to 2700 deg K. The jpg lists "cool white fluorescent" temps at 4200 deg K and "daylight metal halide" temps at 5500 deg K.

It's part of an article on Grow Lights ( https://en.wikipedia.org/wiki/Grow_light ) which Wiki states "may require cleanup to meet Wikipedia's quality standards."

A good place to start.

W/regard to the distance/lumens thing, the inverse-square law (mostly used in physics) applies:

As the distance from the source of light doubles, the strength of the light received is one-fourth of that formerly received.

Made-up example with imaginary numbers (so that the concept is easy to see):
A plant is 4 inches away from a light source and is currently receiving 100 lumens.
If I move the plant (or the light) such that the distance between them is now 8 inches, the plant will only receive 25 lumens.

Cynthia H.

[cynthia_h]

I got the 9 to 1 ratio information from strong scientific evidence of LED lighting .

Please provide the source of this "strong scientific evidence of LED lighting."

The same data applies to fluorescents for full spectrum (sun) lighting.

Upon what authority do you base this statement? Again, provide your source.

Match the lumens per sq. ft. of the sun and you harness its power in a given area.

This is a pretty tall order. I'll be the first to admit that Wikipedia isn't the be-all and end-all of scientific sources, but it does a pretty good job on quick notice. Here's what the Wiki article on "Sunlight" ( https://en.wikipedia.org/wiki/Sunlight ) says:

"Bright sunlight provides illuminance of approximately 100,000 lux or lumens per square meter at the Earth's surface." [emphasis supplied; this is 10,000 or so lux per square foot]

Someone trying to emulate this intensity indoors will, most likely, be converting electricity into light and heat--generally considered an inefficient and environmentally unfriendly procedure. A therefore expensive proposition, both in terms of equipment and upkeep (electricity bills!), to say nothing of the risk to his/her vision (the dangers of direct sunlight).

Shop lights, under-plant heating pads, etc. are minimal expenses relative to the savings realized by not paying a greenhouse company to start plants for you, and many gardeners reap large savings and large harvests of satisfaction in so doing. (True confessions: due to my personal situation, I do a combo of seed starting, direct seed planting, and purchase of plants.)

This is the time of year when many Northern Hemisphere gardeners consider the start of their seedlings very carefully, so that the young plants will be ready to go into the earth at or about the exact time the earth will be ready to receive them. The sun itself will provide sunlight, as all plants and animals have experienced for millennia, and all will be well (in a good year) in the garden.

Cynthia H.

[gixxerific]

Well said Cynthia, I have seen the Kelvin scale before and the grow light article pretty much states what most of us believe, it's at least what I thought.

Still it just strikes me that so many people had so many different ideas of what color was the best. I should have put the links in my thread but I didn't start it until after I thought about it for a bit. Maybe I will try to find them again.

Oh and don't tell anyone but I bought some veggie bulbs today.

[cynthia_h]

Yes, please do add them, either to your original post or to the thread as it stands when you track them down again.

Use the History function on your computer; it will make the whole process a LOT faster.

Hmm...veggie bulbs...are those anything like tulip bulbs? garlic bulbs? How long does it take for them to germinate?

And I forgot to congratulate you on the marvelous haul of FREE small veggie planting pots! Terrific!

Cynthia

[gixxerific]

You got no idea on the pots I was thinking today that I should start a nursery. Really I have a ton and I have 2 nursery's that tell me to take all I want.

Bulbs: well I got onions and potatoes today to go along with my own onions and potatoes. I might need some more pots.

I'll try the history but do you have any idea how much I'm on the PC there is quite a bit of history to go through. Stupid W.W.W. where was this thing when I was in school. Too much info on here.

[gixxerific]

Here are some of the links that got me thinking, good luck:

https://plantphys.info/research/experimenta.html
https://www.gardenguides.com/video-60017-color-light-plants-growth.html
https://www.collaboratory.nunet.net/timber/scifair/seventhn/5.htm
https://www.colormatters.com/science_faq2.html
https://futurity.org/earth-environment/ancient-ferns-bum-a-ride-from-giant-trees/
https://www.oxygraphics.co.uk/whygreen.pdf

That's enough some of the more different ones. There was a great link with tons of other links, very scientific about the different spectrums. But it was on a canibus website so I didn't think that would be cool to link here.

[garden5]

Here are some of the links that got me thinking, good luck:

https://plantphys.info/research/experimenta.html
https://www.gardenguides.com/video-60017-color-light-plants-growth.html
https://www.collaboratory.nunet.net/timber/scifair/seventhn/5.htm
https://www.colormatters.com/science_faq2.html
https://futurity.org/earth-environment/ancient-ferns-bum-a-ride-from-giant-trees/
https://www.oxygraphics.co.uk/whygreen.pdf

That's enough some of the more different ones. There was a great link with tons of other links, very scientific about the different spectrums. But it was on a canibus website so I didn't think that would be cool to link here.

It looks like I have a lot of reading to do . Personally, I think that it is better to use a light that has a "K Rating" for the light color (intensity) than to just paint the bulbs or throw a filter over them. I'm not saying that it won't work, but I just think that it will yield in consistent results.

Also, with regards to Resolutejc's post about "matching the lumens of the sun"; perhaps he meant matching the light spectrum of the lumens of the sun.

[gixxerific]

I was kind of thinking that after I wrote it about the lumens.

I do understand what MOST people would use and quite a bit about lighting and electrical, I was just amazed at the data showing differences to that thinking.

Yeah you should have seen some of the links I didn't post either too technical or just not noteworthy. But C_H asked and she received. I surely don't expect many to read them.

[Sasha]

I've never used grow lights before, but this thread is making me wonder something ... does all this obsessing about optimal spectral qualities actually result in more than a marginal increase in growth? Or is the obsessing just part of the fun?

[gixxerific]

I've never used grow lights before, but this thread is making me wonder something ... does all this obsessing about optimal spectral qualities actually result in more than a marginal increase in growth? Or is the obsessing just part of the fun?

Just for fun, you could grow lights with incandescent lights if you want. It might take a while and waste a bunch of electricity in the process but you could.

I'm sticking with fluorescent 6500k for now it works for me so...........

[rainbowgardener]

I've never used grow lights before, but this thread is making me wonder something ... does all this obsessing about optimal spectral qualities actually result in more than a marginal increase in growth? Or is the obsessing just part of the fun?

I don't really know the answer, but I know you can successfully grow healthy seedlings to transplant size with ordinary fluorescent tubes in shop light fixtures, because I do it every year. Would they be bigger or deeper colored or something if I used more "optimal" spectrum lights, maybe or maybe it depends on what plants and what growing conditions.

I do think fluorescents generally are much better than incandescent. Incandescent gives off so much heat, you can't have the bulb very close to the plants and so the light gets too diffused. And the incandescent bulbs are better than trying to grow them on a windowsill, which is usually not very successful at all.

It is part of the fun and we all have to have something to occupy us until we can get outdoors again!

[gixxerific]

Boom!!!! Well said RG

This thread was about nothing more than that I think way too much about nothing at all.

[garden5]

Boom!!!! Well said RG

This thread was about nothing more than that I think way too much about nothing at all.

Been there, done that. But then again, isn't that what everone says about deep thinkers ?

[resolutejc]

@applestar: Good tip about the leaf burning. But are you sure it's solely based upon temperature? I've had leaf burning in the past from my fluorescents which don't give off heat.

@garden5: Yes, the light spectrum of the lumens of the sun is a 9 (blue) to 1 (red) ratio.

@rainbowgardener: I do not have the physical copy of the science magazine that I read on the topic, but the following quotation lends some insight on the matter. I remember the article addressed (nm) rates and the portions that plants could use fell mostly in the red and blue range. Since blue is higher kelvin and closer to daylight sun, it was preferred to red, though red was still necessary.

"T5 lamps provide the ideal spectrum for plant growth. Photosynthesis rates peak at 435 nm and 680 nm. A 6500K T5 lamp has a spectral distribution with relative intensity peaks at 435 nm and 615 nm. This equates to very little wasted light energy in terms of plant growth. T5 lamps promote incredible health and vigor of seedlings and cuttings. Root development is superior relative to other lighting sources. While T5 lighting is excellent for starting seeds and cuttings, it's also able to produce enough light for full term growth. Because of their minimal heat output, T5 lamps can be placed 6â€

[applestar]

Leaf burning from heat happens quite quickly -- within few minutes to 1/2 hr (I guess) and you will see a rapid, visible damage. In my experience, temperature test, as in "Ooh/Ow, that's a bit too warm/hot" will surely tell you that it would burn the leaves.

The "burning without heat" is what I was trying to describe when I said "too much light without burning" -- I honestly still can't think of how I would describe the phenomenon except to say that it doesn't happen immediately, but within a period of maybe 12~36 hours. In other words, assuming you're checking on them morning and night, twice a day, there's a perceptible change in appearance from the last time you looked at them, then the oddness is confirmed the next time, and by that time, I've usually adjusted the lights. What can I say, they just "don't look right/happy."

I guess I've never really categorized what I'm seeing as "wrong" but automatically adjust the light because I know what I'm seeing means the light is too close.... Sorry for not being able to explain. If it happens again, I'll try to pay more attention.