Thanks for posting this, Pagan. I still am sitting on the fence about a LED light. Only because I have a set up of HO T5 Florescents. I am so close to getting one and was hoping that maybe once my bulbs burn out, then would be the time.

In reference to the above post. I have concerns about the LED's with the burning of leaves that I keep hearing about. With having the LED lights so far away and with the heat given off by them being minimal (which is good). This also means the likely hood of the need for a added heat source? If one does not go with a 'tent' is this then going to reduce what can be put beneath the lights. This would be true with any light source.

All these things to ponder in my quest.

I have to say that the results that Martin, Tracy and Jericson get with the LED lights makes it appealing.

Rick

I first started using Grow lights (HO T5 florescents) only to keep newly started seeds growing throughout the winter months and this is still my main purpose for them.

I have found that when the seeds are started in Jan/Feb. under the lights that they are as far along by mid summer as those that I may have started in the previous fall.

The LED lights when raised so high above the plants reduces the intensity of light, therefore reducing the area which plants will receive adequate light, it seems?

One study showed the way in which the LED lights emit light and it was not focused downward in the same size of the light panel. Significantly less and more so as raised.

These are not question made to cast doubt, just to help make them more understood or their use more effective.

Rick

Good question. Fluorescent bulbs produce light this way: electric
current runs through a filament and excited electrons escape into the
pressurized gas inside the tube. That gas gets agitated and produces UV
which then causes the coating on the inside of the tube to glow. As a
result, that glow escapes in all directions. Fluorescent bulbs actually
need cones to gather all that photon and aim it at something. That's why
shop lights and grow tubes often come with reflectors because they
bounce the photons downwards.

LEDs, on the other had, have
two metallic leads that, when powered, directly emit photons without having to excite
anyone. Called electroluminescence, photons are ejected pretty much the
same way a tennis ball machine will shoot out balls within a narrow area
if it is set on "serve".

BUT. Even if the light cone of an LED
fixture is narrower than a fluorescent bulb, it's still a cone. The
higher you put it above the plant, the bigger the base of that light
cone. The more plant you can put in it. So the area will expand but the light will be more spread out (lower photon density) so the plants will get less light the farther you put them. And also, the outside
perimeter will typically get even less light than the center. So you will
probably have to do what penguins do in winter---they take shifts,
rotating from the center outwards so everyone gets a turn in the prime
real estate.

The important point, though is that the same thing will happen if you put plants farther away from fluorescents. Bigger area, less intense light, longer "on" periods.

Do you have a link to that study, Rick?

This is worth watching:

This link that Martin has posted is so good.

Although the light cone of the LED light may mean that it will cover more area. One has to assume then that the further the lights are away from the plants. They are not all receiving the same amount. If not less all the way around as the light has been taken further away to cover more surface area? The same said for Flourescents or others.

Rick

Yesterday I made the decision to turn off my Mars Hydro LED I had sitting above my seedlings. It was 15 inches above, and still scorching some and stunting others. I don't have the space in my current setup to raise it. Instead, I placed one of the lower wattage panels, similar to what Pagan has, about 7 inches from the plants. Additionally, I had one screw in bulb, which had focusing lenses and drew about 3 watts. At 20 inches away, I was impressed that the growth was so compact. Over time I've began to notice that new leaves aren't growing.

You are exactly right, Rick.

Snap, Dain lol Anyway. Are your plants on heat mats? Also how long is "over time"?

Over time is referring to the last couple of months. And, yes, I have a hear mat underneath.

I do not know whether I am right at all. Just trying to get my head rapped around these lighting set ups.

Pagan, You just introduced a LED light I believe recently. Didn't You?. How is this working for you.

Rick

They're working out pretty well, Rick, except for the problem I talked about at the beginning of this thread. But now that it's resolved, I shall wait and see. Remember though that I am using these LED grow lights in the dark and cold basement. My hope is that the adenium there will go semi-dormant once it gets really cold. Well, one started to bloom lol I suppose that's because it's still pretty warm in there, 20C at night.

Pagan

Dain, since you're using less powerful grow lights, you'll have to move them closer to your plants. Also, note that sometimes adeniums seem to stop growing new leaves and it is this time when they spend energy to enlarge their roots. Check out Mark Dimmit's article .

For what its worth if you google LED vs MH ( metal Halide ) reef aquarium. You can get pictures with PAR readings. I have never used LED but they seem to give more PAR than t5 and Metal Halide. Of course Brand and quality comes into play when trying to find the right light.

Yeah, Kerry. Except for the up-front cost, shifting to LED grow lights is really a no-brainer. Having said this, if I did not have to expand my winter plant shelf, I will probably do as Rick is doing and wait until my T5HOs burn out first, replacing them with LEDs as they go. As it is, I only got them for the additional shelves I needed this winter and they work great.

Low PAR is only one of the myriad of things wrong with metal halide bulbs.

Pagan, the tallest are 5.5 inches from the panel, and shortest are about 7 inches from the panel. I think this should be close enough.

LED grow light technology keeps getting better every year. Since I live in a north facing window apartment, my light is on 12 hours a day. However, my plants are thriving so I know how effective they are. I like to research which lights are currently the most reviewed and highest rated, then upgrade when I get more plants. Check out some reviews before you buy.

LED grow lights can put out a ton of intensity for the power that they pull, but its also easy to burn your plants if you're not careful. This table is useful as a rule of thumb to make sure you are keeping your lights the right distance away from your plants to avoid light burn.

Nice thread. Thank you for starting it, Pagen. Some useful discussion here. I'm with you that I despise the blue-red light setups that make everything look intense pink. I won't ever have that in my house. The rest of it interests me and so far my adeniums keep having to go winter dormant. I'd really like to move towards a better set up in the new home for next winter where I can keep them actively growing if I can, but it'll take some planning.

Just bought a 1200 watt LED grow light full spectrum with a veg and Bloom switch on it can I turn on both the veg and Bloom switch on at the same time or just the veg switch my plants are approximately a foot and a half to 2 ft High appreciate any response

I have an led light that has a vegetative setting and a flowering setting. The question i have is do you just turn on the flowering and turn off the vegetation when wanting to flower?

It depends on the light, actually. For the most part, to be entirely honest (and I'm going to get a lot of argument, screeching, arguing, and people insisting they have a magic formula), it's just not as straightforward as Veg and Bloom. Nature does not work that way. The sun does not suddenly irradiate plants with oodles of blue or red light when it's time to flower or blossom, and indoor plants are no different.

The vast majority of plants will want both settings on at most times for maximum energy output if the lamp can handle it and if the plant in question wants it.

The Veg setting--depending on your lamp--ramps up the blue (or ramps down the red) by some amount. The flower setting ramps down the blue or ramps up the red.

If it's reducing energy overall to below what the plant likes, that's a problem. Keep it at a higher setting overall even if the spectrum is a little too blue/red.

If it's over what a plant likes, pull it back. Again, even if it's too blue/red. Note that this isn't usually a problem.

And check the species in question. Some are more particular than others, and there are too many indoor crops to count. Most, frankly, simply don't care.

What do I use? I use a mixed-spectrum of LEDs of warm whites, full spectrum, mid-white, and red. It covers the output from 395 to 800 nm with no gaps, including the allegedly "useless" yellow and green areas of the spectrum (they're not useless, they've been omitted due to historic reasons that are no longer necessary; plants do use them). The system in the room I'm sitting in has been designed to be not terribly unpleasant to my eye (which is extremely particular in terms of color; I paint in this room; the light has a noticeable red-violet cast to the white, but can be easily overwhelmed by my painting lamps and I've learned to compensate).

It's assembled less by spectrum than light strength, and plants do beautifully under this one, the one downstairs, and the less-well designed one in the bathroom (very noticeably red).

Flowers get sprouted, and blossom easily, every year under the lights in the cellar. Those are the cheapest fluorescent tubes I can source, 850 plants a year, raised from seed with no other significant light source. Most are budding to blossoming by the time they go outside in May. I just use 1 warm white and 1 cool white per lamp, 2 lamps per shelf, 6 shelves.

In case anyone is wondering---five years hence and my adeniums absolutely do better under LED grow lights in winter, they even bloom if I keep them warm with heat mats. I no longer bother--I just put them on the top-most shelf where they are warmed by the heat rising from the light panels in lower shelves. In my set-up, the winter growers are on the lowest shelf where it is coldest.

And I no longer use that screw-in LED bulb. It's just too annoying to manage and it requires too much vertical space.

Thanks for the update! I keep mine under LED bars, personally, and let them go into dormancy if they want. They usually break it naturally in January or early February from indoor temperatures (they're out of it now) and the lights go on.

As you said, indoor house temps are fine. For me, the "lowest" shelf is a windowsill. :-)