Grow light recommendations

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jbergeson
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Grow light recommendations

Post: # 66409Post jbergeson
Wed Nov 01, 2017 6:12 pm

I know we've had a thread on this fairly recently, but I wanted to bring it up again to see if anyone has any "bright" ideas for creating a growing area.

For any newbies, I think it should be noted that it is likely a waste of money to buy special 'grow light' flourescent bulbs...it's more about getting the most light out of the bulb, which is probably from a Cool White high output T8.

Then what about white LED shop lights from Costco or Lowes, etc? My assumption is that the quality of light would be just fine.

Of course the m8rEwanna growers are the experts, but LED arrays sold to them tend to be super expensive and a combo of red and blue LED's that makes everything look purple.

I'd like to create a growing area about 4' x 8' that allows for plants of heights up to 4 feet or so - I have a lime tree in a pot that would be fun to keep actively growing for the winter. So I thought maybe I could find a good deal on a bunch of cheap 4' cheap LED or T8 shop lights and mount them fairly close together.

I'm too lazy to do serious research at this moment but thought I'd start a thread if anyone has any good ideas or scoops on where to get cheap but bright lights.

bvanderhoek
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Re: Grow light recommendations

Post: # 66410Post bvanderhoek
Wed Nov 01, 2017 8:58 pm

Probably the plain ol' T8 shop lights will be the most light for your dollar. I have a 55-gallon fish tank with (of course) real plants, and the light fixture is a special red, white, and blue LED (purchased on Amazon) that is supposed to provide all the kinds of light the plants need. They do seem to grow well under the light, and it is cooler than fluorescent. Maybe, though, if you are growing roses in a damp basement like I did when I lived in Minnesota, the warmth of the fluorescent lights would be in their favor. LED lights like my aquarium light do cost more, but you don't have to replace the tubes, so that may be a point in their favor. Let us know what you end up choosing and how it works!

henry kuska
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Re: Grow light recommendations

Post: # 66411Post henry kuska
Thu Nov 02, 2017 12:03 am

My understanding is that LEDs do not have the gradual decrease in light intensity that fluorescents have.

tsilvers
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Re: Grow light recommendations

Post: # 66413Post tsilvers
Thu Nov 02, 2017 10:01 am

Hi Joe,

I've never done any real scientific comparison but have always just grown all of my seedlings (rose and otherwise) under ordinary cheap fluorescent shoplights in my basement. I also overwinter bigger things like small citrus trees and a pineapple plant and everything seems fine with the cheap shoplights. I know the bulbs are supposed to decline with age, but to be honest, I got lazy and haven't even swapped out bulbs for 3 or 4 years now. I'm still getting acceptable results. I have them hanging on chains so I can adjust them up or down with "S" hooks.

This past winter I bought two relatively inexpensive LED shoplights to try out and these seem to be working well too. I started a bunch of Citrus and Calycanthus seedlings under these and they all seemed very happy.

Good luck with your set up!

Tom


philip_la
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Re: Grow light recommendations

Post: # 66422Post philip_la
Fri Nov 03, 2017 1:31 am

LED's don't really cost that much more (search online for sources) and will save you a good deal of money in the long term due to their long life and lower energy consumption. They don't fade out as quickly as flourescents, and don't put mercury in landfills. You can easily google either "spectral analyses of..." or "spectrometer charts" and see that the newer lights have very full spectrum (high CRI's or "color rendering index" and show true colors) and many have little peaks in or around the blue range. (I think the blue is the primary color emitted from the led and the others come from phosphor coating, if I recall correctly.) In principle, it seems LEDs should compete very favorably with flourescents, but I don't know enough to draw any real conclusions. I suspect you are ideally wanting to match the absorption spectra of the two chlorophylls?
Dunno if it means anything to those more in-the-know, but it looks like the peaks in a 3500k led align moderately well with the absorption of Chlorphyll b with the added benefit of actually permitting one to see the plants as they appear -- generally much truer color than with a flourescent bulb, typically having a CRI around only 60.
LED's don't require ballasts, but you *can* get tubes that can be popped into a flourescent fixture without having to rewire to bypass the ballast.
Philip F.
[size=small][color=#669966]Zone 8 / Sunset Zn 30 (Austin, TX -- formerly New Orleans, LA)[/color][/size]

philip_la
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Re: Grow light recommendations

Post: # 66423Post philip_la
Fri Nov 03, 2017 1:59 am

1000bulbs.com has T8 1800 lumen 3500k replacement LED tubes for about $7, but if you can, you might do better to avoid the ballast of an existing fixture. The same site offers fixtures as well as panels, and panels come to about $15 per 1000 lumens in the 3500k color. (Don't take my word on appropriate color though!) With a life of 50,000 hours, you will probably never replace, unless you get a dud.
https://www.1000bulbs.com/category/led-panel/
Philip F.
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david zlesak
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Re: Grow light recommendations

Post: # 66428Post david zlesak
Mon Nov 06, 2017 3:07 pm

Hi Joe!

This past winter with more space in a walk out basement I got more stands and lights. I really like the bright white LED shop lights. Each brand I think may have a different spectrum. I called and eventually got a spectrum graph from what Sam's CLub was selling (about $35 for a 4' LED shop light) and it looked kind of comparable to cool white florescence (good blue and a bit less red). The lumens were about 4200 or 4500, which was nice. With LED's so directional, I suspect you may like to use at least some LED's above your plants as you have some tall plants. It'll help direct more light downward to them than a florescent light that high in the air diffusing light more directions. Menards has a nice 4200 Lumens one that is lighter weight and not as wide with a diffuser and about $32. With that one I like that they are narrow and can accumulate more in tighter space then to get a lot of light over an area.

I also kept some of my florescent lights too and on many shelves put one LED and one florescent one too. Some of the other species I grow (ninebark seedlings, etc.) seem to be more particular to light quality and stall out under typical cool white florescence, but when I put grow lights in them with more red they grow well.

At Menards at least by me in the electrical dept. they are selling LED strips that have red and blue for photosynthesis for $30 each. They come in square long units that can be linked together. They are about 18" or 24" long and $30 each. I haven't bought one yet to see how much light they emit. It seems kind of expensive to me to cover a shelf. Maybe I should just try one and see how the plants do.

patrick

Re: Grow light recommendations

Post: # 67506Post patrick
Thu Apr 05, 2018 1:57 am

If you are going to use LEDs to make a grow light, I would suggest using a SunLike LED module like this.
https://www.knema.com/high-cri-for-the-best-color.html

philip_la
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Re: Grow light recommendations

Post: # 67513Post philip_la
Thu Apr 05, 2018 11:47 pm

I'm not sure what the policy concerning marketing on this site is, but I feel compelled to point out that CRI, or "color rendering index" is a measure based on human photopic vision, and is designed for *appearance*. The broad spectrum of a high CRI module attempts to include all the colors that our eyes will sense, to create colors that appear richer, truer, and more saturated to our eyes.

But plants and humans use light differently, and since the whole point of LED's is to decrease energy consumption, there is no efficiency to be gained in using lights that are marketed as full spectrum since much of that spectrum will serve no purpose in photosynthesis. Grow lamps typically attempt to target a good half dozen or more specific wavelengths associated with photosynthesis in an attempt to maximize the "Photosynthetic Active Radiation" --PAR for short -- which the plants utilize. (The most efficient create a light which to our eyes has a creepy purpley color.) Your "SunLike" module isn't necessarily the best choice for plants. Cheaper lights with peaks in appropriate locations might actually be more efficient in the long run than high CRI "sun color" lights. (Evaluating seedling coloring under a true grow light would be nightmarish, however.)
Last edited by philip_la on Fri Apr 06, 2018 11:06 pm, edited 1 time in total.
Philip F.
[size=small][color=#669966]Zone 8 / Sunset Zn 30 (Austin, TX -- formerly New Orleans, LA)[/color][/size]

Larry Davis
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Re: Grow light recommendations

Post: # 67514Post Larry Davis
Thu Apr 05, 2018 11:53 pm

A couple years ago there was a long thread on this and Peter Harris did some research. I also found a definitive analysis by someone at Utah State who had compared the total energy output per $ for average lifetimes of LEDs and tungsten halogen or high pressure sodium with a couple fluorescents. He had earlier worked for NASA on figuring out how to grow wheat in space most effectively and did a really thorough analysis. The conclusion was that LEDs do not yet compete with HPS and hardly beat standard T8 fluorescent for overall photosynthetically active energy per $. The plant uses a different spectrum than our eye so what looks really bright to us is not so for the plant. The specialty crop growers use the red and blue combo instead of white because it puts the energy where the plant can use it best.

The ~ 10x capital cost of LEDs is what makes them non-competitive in a greenhouse situation where you want to light a relatively wide angular area beneath the light, calculated over a 5 year period. As the initial price of LED units comes down they may get more favorable if you can't take the heat of the HPS or tungsten halogen. But for cool basements the warmth may be a (relatively expensive) benefit. If the quality control for LEDs (including power supplies regulators etc) gets better so they last longer, their competitive position will improve.

I finally got up out of my chair and found the article. Jacob A Nelson and Bruce Bugbee (2014) PLOS ONE vol 9, issue 6, e99010 Economic analysis of greenhouse lighting: light emitting diodes vs high intensity discharge fixtures. (available free online.) They tested 7 HPS, 10 LED, 3 tungsten halogen and 2 fluorescent types. In a greenhouse the size of the shadow is important, as it blocks good quality sunlight. So different shape fixtures and innovative hanging strategies are important considerations. In a basement with the light above everything, shadow is irrelevant.

philip_la
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Re: Grow light recommendations

Post: # 67548Post philip_la
Fri Apr 06, 2018 11:01 pm

The rate of development of LED's has been astronomical, and I would argue that a paper written in 2014 is no longer germane. A $60 module requiring a $60 HLV dimmer five years ago, for instance, is today obsolete when compared to a comparable $7 module working with a standard dimmer. (My city does sometimes supplements the purchase price of LED's to save electricity and resources, so I get a particularly good deal on bulbs, I should admit.)

In the last few months I have seen LED fixtures that compete in price with the T8's, and it's worth noting that the energy savings over fluorescent is not insignificant.

This quick search provides a good example:
https://www.homedepot.com/p/Lithonia-Li ... /203409289 vs.
https://www.homedepot.com/p/Lithonia-Li ... /205527766
Note that the second fixture has no bulb, but the bulb purchased *will* have a worse CRI than the first, cheaper LED fixture, and the bulb will need replacing several times before the LED would fail.

So, in view of their longevity, there will be extensive savings in purchase price of bulbs over a several year period, and the lumen output of an LED doesn't drop as quickly as with an older fluorescent. (LED's also don't contain mercury.) Having said all that, if the last 5 years are any indication, the price will continue to drop rapidly while the technology improves, which makes the pressure to purchase less... well... pressing. (How obsolete will my bulbs be by the time those damned things need replacing??)

The horticulture market is *not* as large, obviously, as the home consumer market, so the drive to develop isn't as strong. I don't know how much advancement there has been in modules used as grow lights over the last few years.

I have admittedly never liked fluorescent lighting, preferring *any*thing incandescent, but I am now a complete convert to LED.
Philip F.
[size=small][color=#669966]Zone 8 / Sunset Zn 30 (Austin, TX -- formerly New Orleans, LA)[/color][/size]

Plazbo
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Re: Grow light recommendations

Post: # 67549Post Plazbo
Sat Apr 07, 2018 12:32 am

I can't recommend anything specifically but I use a lot of LEDS in various planted tanks...not exactly the same purpose but the same principles come up.

If you want to minimise electricity usage while maximising wavelengths for photosynthesis you'll be looking for peaks between 420-450nm (blue) and 600-700nm (red)...this leads to the typical purple/pink light that's sometimes seen with people growing things inside. Outside that range things are either not used, offer only minor use or are primarily for human use.

So part of it will come down to whether you want the lights to be purely for growing or for growing and viewing.

Don
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Re: Grow light recommendations

Post: # 67550Post Don
Sat Apr 07, 2018 2:57 am

>> you'll be looking for peaks between 420-450nm (blue) and 600-700nm (red)

It often happens for me that seedlings under lamps in the nursery have a very different appearance than they do after they are let out to play. The reason for this is that the wavelengths of light a plant sees affects regulatory processes as well as photosynthesis proper. There is a critter plants called a phytochrome that is sort of their pituitary gland that responds directly to the wavelengths and duration of light.

https://en.wikipedia.org/wiki/Phytochrome

LED's or fluorescent's do no harm in short term nursery operations but keep in mind that light affects regulatory processes as well as photosynthesis proper. They may actually affect germination. Dr. Kuska has done some experiments with germination of roses under red light iirc.
What doesn't kill them makes them stronger.

Larry Davis
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Re: Grow light recommendations

Post: # 67553Post Larry Davis
Sat Apr 07, 2018 3:19 pm

Yes, Don is correct about red/far-red. That's phytochrome. "Pigment of the imagination" is a book that discusses its history up to a couple decades ago. There is also a blue light responsive substance which I think is called cryptochrome. Either one can lead to epigenetic changes. Plants recognize long or short days, also cold winters, by methylating/demethylating DNA or the histones that hold the DNA together in chromosomes. I don't know of, but strongly suspect, small RNA molecules may also be involved in some of the light-dependent signals. Whether the epigenetic changes last more than a year, or even more than a generation is unclear in plants, fairly certain in animals for some, maybe many genes.

patrick

Re: Grow light recommendations

Post: # 67563Post patrick
Sun Apr 08, 2018 10:00 pm

Yes, a high CRI is not a great indicator for a grow light as you can easily achieve high CRI values by mixing in LEDs of a specific color to boost the rating where a fixture is lacking that color. But the SunLike LED doesn't do that and instead gives you a true full-spectrum light source.

Plants see all the light between ~400-700nm equally, as explained in the below video.

https://www.youtube.com/watch?v=TszB2A3bdYc

LEDs like the SunLike LED give you more photons of light that are usable for photosynthesis because you have higher emissions of more usable wavelengths in that range of ~400-700nm.

Image

Although admittingly the output is not nearly as high as some of the other LEDs that concentrate on only far-red wavelengths. This, however, might not be an issue as new studies like those done in the video below in photosynthetic efficiency seem to show that plants use light more efficiently at lower light levels anyway.

https://www.youtube.com/watch?v=D-uLwapyCUo

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