I started lettuces on 10/23 and they were just showing green, under my usual florescent bulb starting mechanisms, when the power went out for five days. I was worried that the sprouts would be too leggy and get my trials with an LED array off to a bad start, but after watching for a few days, these look fine. I guess that the cooler house temperatures also slowed development.
The light is an Illuminator UFO 5-Band Tri-Spectrum LED grow light. I vaguely thought that I would start with simple lettuces but the leftovers from last spring didn’t really offer that choice, except for Simpson Elite, a popular leaf lettuce, so I started two rows of it. And a row each (four 2″ soil cubes) of Australian Yellow (leaf) and Yugoslavian Red, my favorite heading lettuce. A row of Red Velvet didn’t germinate for some reason, I have had that problem before with that seed; this was a replacement pack. Thus, the empty cubes in the last picture.
In spite of plans to take advantage of extra basement space with a well-designed setup, in my usual haphazard way, I stuck the light in the guest/junk room. It uses the very sophisticated setup that I use in spring, two cross country skis over the tops of chairs and chains to hang the lights. I left one florescent fixture in place for times when I want to work with the lettuces. In just the time it takes me to get from the door to the outlet to unplug the LED array, my eyes are already complaining about the lurid pink glow. And everything is green while your eyes recover.
If anyone has advice about how long these lights should be on for lettuce, please speak up. I keep the seed starting lights on for 16 hours a day but I think that may be too long for these. Also, I suspect that day length has something to do with lettuce “heading up” so I’m thinking I should plan for some room to increase hours for that heading lettuce when it gets bigger. I have been warned that lettuces grown under low lights could have dangerous levels of nitrates, and did some reading on that. I do not know if “low light” applies to LED arrays. And about the only plans I have to deal with this is to use a low nitrogen fertilizer and get one of my lettuces tested at harvest time. I’ve also read that foods that have this problem taste bad so, guess what! I won’t eat them if they taste bad!
With low light levels will the lettuce keep growing well and green without the lights? Now, how much is the lettuce going to cost? I am running a meter now on certain electronic stuff to see how the power is getting used. Somethings are way more power eaters than I realized
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Hi Marge! The information on low light, nitrate/nitrites that I found was mostly about poisoning in animals. Some people mentioned hydropic issues but didn’t talk about what kind of lights were used. So evidently, lettuces can look edible under low light condtions and not be good. LED arrays are in the most useful bandwidth for the plants so are much different in the way that they work than HIDs, which were mimicing the broad spectrum of white lights.
Further advantages, these don’t throw off the kind of heat that older grow lights do and they use dramatically less energy. I should get a meter to check.
So I asked, how many hours a day should these be on the lettuces? (I have them at 12 hours right now.)
Additional question: what does damage due to too much light, lights too close, look like?
The plants are developing new leaves but also a longer stem than I see outside. I would move them closer to the lights but I’m worried about the damage as these are so small. I would not think that lettuces require wind/a fan but let me know if you thik I’m wrong.
I’ll take pictures about Wednesday for a one week report.
A few things to note:
Leaf lettuces tend to be low light plants, so you can get away with using less light than you would say a tomatoe plant or chili pepper, which makes them great for use under low power LED’s.
Stretching of the plants during growth is general an indicator of either not enough of or not the right kind of light, (More blue light encourages growth, or the lack of overall intensity of light and can make the plants “stretch”). Since LED grow lights provide only the specific frequencies of light that plants use, the mix of colorings in your LED’s is important. Further that the LED’s emit the correct spectrum and cheap similar looking LED’s are not used because they do not put off the correct spectrum of light. In the case of broad spectrum LED’s, as a primary light source, I find I need to keep the light sources within 1-2 ft of the tops of the plants to get adequate light, depending on the intensity of the light source. Since excessive heat output is not an issue with LED’s, I’ve even gone as low as 6″ using a 45w panel, just to get as much light into the crop as possible. To this I would add the use of 2mm Mylar around your grow in orde to reflect as much light back onto the plants as possible. This just maximizes the bang for your buck on yoru energy consumption.
Time of exposure is also a matter of the intensity of light. But 12 hours is a magic threshold where plants will revert from “summer” growth mode and switch to fall fruit / blossom mode. (Your nutrients will also play a part in this, so that statement is not an absolute.) But think of the light timing more as a matter of exposure of a quantity of photons needed for photosynthesis. Using a low wattage light source, you would need more exposure time then as compared to using a higher wattage source, which could put out more photons in less amount of time. So adjust your exposure time based on the plants overall light needs and the size of the light source you have.
I’ve not heard about the build up of nitrites due to using LED’s, but in our experiements in hydroponics to see how long one crop could be sustained off of one dose of nutrients, we found that we could sustain a crop for several months, but the lettuce would start tasting bitter if their was any problem at all with the nutrient balance, including pH. pH is probably your most imporant to watch out for in a contained grow environment because it can cause the wrong nutrients to be absorb, or the right ones to not be absorbed. Simply to say that you can have all the right nutes, but if your pH is wrong the plant will not absorb the nutes appropriatly.
Comparing HID lights to LED’s is somewhat difficult. Those lights produce about 90% wasted energy between heat that plants don’t use, and light energy that is not in the spectrums that plants can absorb. The reason they work is the shear bulk of output is sufficient enough in the specific spectrums, that plants manage to grow. Since LED’s only produce the exact spectrums of light that plants absorb, and little heat, there is less wasted energy. The trade off is the intensity of the light source is lower. The jist of these you will in the fact that plant leaves are green under normal white light, but nearly or completly black under an LED grow light. This is because pants do not absorb green light but reflect it, since LED grow lights are not producing any wasted light, there is nothing to reflect, therefore the plants look black. (The amount of coloring varys from plant and variety.) Which BTW is another great way to tell if plants are “sick”. If the leaves do not look black under the LED lights, it’s a good indicator that optimal photosynthesis is not taking place and something with the health of the plant is a problem.
I would suggest using hydropnics indoors. Our use of soils indoors was frought with problems of soil born pesticlence that was only eliminated by eliminating the soil.
And lastly, how to figure the cost vs energy consumption; If you’re just going for shear bulk, there is no comparison, commmercial operations can alwasy do it cheaper. That does not mean they do it better. My first point of consideration is the quality of the crop I can produce vs what I can buy in the store. Next is the fact that I can harvest fresh as needed, instead of going to the store, buying and storing. So if you include in your costing the cost fo gas to go the grocery store, the price of the food, and the cost of storing it (refrigerator energy cost), then the overall cost comparison starts to even out, add in the quality issue, and growing your own, even indoors is worth it.
Thank you; a lot of good considerations here. I have plans for a better and more permanent setup for these lights and plants and will look at the Mylar. I need an enclosure, anyway as the area that I’ve designated for a more permanent spot is open to the cats. I may move to hydroponics, we’ll see. I’m building on the experience that I’ve had of lettuces growing to near-edible size, just under my florescents. The mix I use is sterile; Pro-Mix. Although the second batch was mixed 1/3 with compost (the one part). It will be interesting to see if there are “contamination” problems.
I should add that the reason I’m trying compost in the mix is because of micro-nutrients. I am not convinced that we understand ALL of the needs of plants to the point where a fertilizer mix can provide them. And I’m too lazy to make compost tea. Which might have some of the same down-size of contamination, if this is to be a problem. My mind is WIDE open right now.