Any LED grow light recommendations?

Factual Questions
1

I have been growing plants indoors under lights for a long time using fluorescent light setups (T-12s, then T-8smore recently augmented by a couple of 8-tube T-5 fixtures).

Results are pretty good in general, but mediocre for raising some kinds of seedlings (like tomato plants, which get leggy) and for higher-light requiring plants, i.e. orchids and certain tropicals.

I have an older HPS fixture which blasts out too much heat to be very useful indoors, so the idea of a bright LED fixture with very low heat output is appealing. I know very little about these however, and the info available online is limited by several factors, including 1) there seems to be a lot of dealer spam* on forums, 2) strong opinions and anecdotes trump science and practical info, and 3) many postings deal with raising pot, and what works in that setting probably wouldn’t translate into my kind of gardening.

What I’d like to find is an LED fixture or fixtures that will cover at least a 2 x 4 foot area adequately (the area of a tray on one of my plant shelves), be well-made and have a long working life, and sold by a stable company with an adequate guarantee.

Any recommendations? *(suggestions from brand new registered “guests” are likely to be ignored).

2

I don’t know specifics, but I would suspect that it’d be difficult/expensive to get LEDs with enough UV output in them.

3

Sounds like you’re low on the red end of the spectrum. I added a HPS to my fluorescents and got very happy looking tomato seedlings.
I’m not finding much on reddish LED’s for plant growth, except of course among the cannabis farmers, and that lot’ll believe anything.

4

Comparing the spectra of common fluorescent bulbs,white LEDs, andcolored LEDs, it looks like you can match anything the fluorescents produce with LEDs outside of UV, and I’ve seen that UV LEDs are available, so it sounds like some kind of combination might work.

I’m not sure what your concerns regarding heat are. With LEDs you shouldn’t have to worry about IR in the light, but if you are using a lot of high intensity LEDs, you are probably rectifying a lot of AC and producing a lot of heat in the power supply anyway.

When I used to keep saltwater fish, I tried all sorts of lighting to promote algae growth, but nothing worked as well as sunlight. Maybe there are sunlight channels that could help you out.

5

I do not know about LED’s but HPS or Metal Halide lights are the best for indoor growing. Since you are worried about heat there are other options.

I recommend using florescent lights and hanging them about 2 inches from the top of the plants. Hang them with a chain so you can adjust them as necessary. Behind the lamps themselves you should but some type of reflective surface. Aluminum foil works great, or you can spring for some mylar. To maximize the effectiveness of the light you should have mylar or aluminum foil on the walls of your grow room or at least something to reflect as much light as possible back to the plants. Do not use mirrors, these are terrible at reflecting light efficiently.

6

Excessive heat is a problem when growing seedlings, as it encourages lank, leggy growth. As an example, once they’ve germinated tomato seedlings do best with a high temp of under 70 degrees. If your home is already near that, the temp under an HPS or MH lamp could well soar into the upper 80s.

One reported advantage of LED is the lack of heat (leaves can supposedly touch the lights without burning), as well as consuming considerably less power.

The downside is that LED fixtures are expensive, and some people have reported early failures with highly touted lamps. Apparently these are not the sort of fixtures where you can just pop in replacement diodes when the original ones fail.

As noted, I do use fluorescent lamps and most plants perform well. I’m looking for improvements in growing seedlings of sun-loving plants and other high light-requiring ornamentals.

This is my current basement setup.

7

I have no experience with LED lights, but have LOTS with metal halide and fluoros and growing ‘starts’ and seedlings (both veggies and woody plants, fwiw). I have grown from seed many, many species (bonsai starters and lots of veggie stuff) and also have kept numerous lps/sps-type coral/reef tanks in the past. I spent waaaay too much on metal halide lights as well as VeryHighOutput fluoros, but quit that stuff before LED’s were available (unfortunately).

IME with seedling/sapling growth, I always got much better results by dropping the (coolish compared to metal halide) fluoro bulbs practically atop the emerging plants and have a fan to move air a bit around 'em. Typical bulbs do not get hot enough to harm most seedlings (ime) and the photon flux is MUCH higher (inverse square law and such). I also would have much more reflective surface above/around the lights so more of the ‘energy’ is sent onto plants instead of into areas where it does no good. See how bright the ceiling is in pic? Wasted energy as far as growth goes, imho. Put foil across/between fixtures of each shelf and maybe hanging downwards off each side of light fixture(s)/racks, etc…every bit helps. It does make a huge difference as I checked the energy on my plants with a borrowed light-meter thingy once to see how effective my ugly-as-shit foil construct was; foil worked so well I ignored the inherent cheapo-look ugliness and went with much better ‘functionality’, so to speak. Wife understood, fortunately :smiley:

All the tomatoes (et al) I’ve grown seem to love having the lights as close as possible and I have had no legginess issues whatsoever. Never has any leaf, stem, or bud shown any unhappiness when the bulb actually touched the plant tissue - plants would grow right up into, and through, the fixture until I raised it appropriately. Of course, the plant must be adapted to such energy-levels and a plant that has never had such intensity upon it will likely suffer if not acclimated to it. I used lots of these fixtures, even putting fixtures sideways along the shelves’ sides so there were lights pretty much 180deg or more around plants/shelves and I could see improvements right away. It did make it a hassle to mist/water things, but the effort was worth it by all means (!).

Using a modest fan really helps with ‘damping off’ of tender species as well as keeping heat from building up under the ‘canopy’ of lighting so I highly recommend moving the air around as much as reasonable. I went so far as having a fan at either end of shelves and alternating them ~hourly so that plants got wind from more than one direction (avoiding a bent trunk, per se but not a prob with most stuff). I don’t think it was really needed but I had an old programmable controller device that made it really easy to set up (or I would not have bothered). Damp-off disappeared after using gentle ‘wind’ to keep plants, not soil, drier overall, fwiw.

Spectrum is semi-important, but I think OP understands that concept well enough. Usually, there is no need to worry much about those super-expensive ‘special spectrum’ lights as typical bulbs are good enough, relatively speaking from my experiences. You may get somewhat better results by spending big money on ‘special’ bulbs’, but IME its a waste overall. My results were similar using expensive ‘special’ bulbs or cheap ‘industrial’ fluoro bulbs, and that included a comparison of growth between two similarly-planted trays of 'maters. YMMV, of course.

Basically, I see plenty of room to add fixtures for additional energy output and LOTS of need for ‘reflective surfaces’ to focus energy where it is useful to plants -> couple rolls of alum foil would do wonders for that set-up, imho. And maybe take off those covers from wider fixtures (such as the fixture in top/right rack in pic) that are meant to diffuse the light and worry about reflecting light onto plants instead.

Nice set-up, and hope OP keeps up the good work. Growing plants has great, and often tasty, rewards within.

8

You may realize this, but be wary of using those spectra plots directly for comparing their intensities. They look like plots of raw data, where the sensor has an offset in the number of counts. That is, it registers a non-zero value even if there’s no light. It’s most apparent in the third plot, where there’s that unnaturally straight line at about 150 counts. Note also that all three plots have the warning “This spectrum is not calibrated for intensity.”

I don’t do measurement of light intensity, so I’ll defer if someone more knowledgeable says otherwise, but I’d at least subtract off the minimum from each plot (about 150 in all three) before comparing relative intensities. It’s almost certainly not that simple, but that’s the best you can do without knowing how the sensor behaves.

9

Well I assumed much more info was necessary. I was just considering the light spectrum. It sounds like the OP is growing veggies or flowers, so I don’t have any specific info about that. My first thought on intensity was its going to take a lot of LEDs.

In case anyone’s interested on growing algae in fish tanks, outside of sunlight, I had great success using an incandescent gro-bulb on a clip on light. Just clip it to the top of the tank and aim it a few inches from the side. Of course it will work well for growing algae on the glass, but counterproductive for getting light on rock inside the tank.

10

Ionizer packed a lot of good information into his post.

More light, being more concerned with total lumens than with specific spectrum. You can get more red by using a mixture of warm and cool fluorescent tubes. And do get rid of those diffuser panels.

More reflective surfaces; white plastic sheeting is actually more reflective than aluminum foil and it doesn’t make for concentrated hot spots due to wrinkling – garden or hydroponic shops will be more likely to have it than hardware stores.

Get some fans in there. Not only do they help disperse heat, they also cause the plants to become more sturdy vs leggy from the physical buffeting, and they disperse the gasses that build up around the plants in still air.

Replace the fluorescent tubes. If they’ve been running for a year, their output is seriously diminished. Growing under lights is not a very green operation. :wink:

And FWIW, tomatoes and cannabis have just about identical ideal growing conditions … so beware the advertising hype, but feel free to listen to those guys.