Choosing Lights for Microgreens
Episode 026 of the Microgreens Podcast
Choosing a light to grow microgreens from the 1,000’s of choices is a daunting task. It is also one of the most common questions I see people ask in Facebook posts and on the web.
As long as you look for a few key tech specifications I mentioned in Episode 26 of the Microgreens Podcast you will be okay. Don’t let the multitudes of choices worry you; almost any light will grow microgreens.
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Previous Podcast on Lights
Here is a link to an early podcast I published on microgreen lights.
Published Articles on Microgreen Lights
Recommending lights for microgreens is a dynamic exercise. The playing field is constantly changing, and experiences are always evolving in many ways. So, of course, there will be many articles published and recommendations for changes.
Going with the more recent recommendations (this article) is always the best bet; however, information can be gleaned from older publications.
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FREE Home Microgreens Grow course that teaches you the basics of growing microgreens in your home! There are 12 video lessons (over 120 minutes), downloads, and more written information and tips!
Published Articles on Microgreen Lights
Most Recent Article
An article on what LED lights not to buy!
Links to Some of My Favorite Lights for Microgreens
LED Shop Lights
Short LED Grow Lights – using these now and liking them!
Higher powered LED grow lights I use for lettuce & some microgreens.
New Lights I’m testing
Show Notes and Transcript of Choosing Lights for Microgreens: Episode 026 of the Microgreens Podcast
Welcome to the Microgreens Podcast, episode number 26. Today, we’re going to be talking about lights.
People spend a lot of time and energy researching, “What are the best lights for microgreens?”
So in this podcast, I want to just talk about my observations about using all kinds of lights, and I’ve used many of them.
I’ve used 4,000K Home Depot shop lights. I’ve used those stupid octopus, or whatever kind of lights you want to call them. They’ve got the three strands, and they come off and they hang over the trays and they’re all purple. Don’t ever buy those. The one thing you’re going to get out of this, I’m going to tell you things not to buy. And as far as recommendations, I’m going to tell you a lot of things that you can use.
But, back to the lights. I’ve used those really cheap, off of Amazon, Chinese, 6,500K, and I’ll talk about what the K value means later, shop lights. On my larger setups, I now use Barrina tube lights.
They work really well, and those are all of the LED shop light type varieties. I also have tried a lot of grow lights, some sent to me, some I’ve bought. These include, like I said, those spider lights. Just don’t buy those spider lights. If you see anything that’s got three prongs coming off them, and lights hanging over, and they’re all purple, and they show these beautiful plants growing underneath them, don’t believe it. It’s just BS. Just don’t do it. So, don’t get those.
But I’ve also tried some Lediland full spectrum grow lights, Vivosun full spectrum grow lights, Happy Leaf grow light. You’ve seen the Mars Hydro SP150s, and now I have the Mars Hydro, I think it’s TLS2000, I’ll be putting out a video on those soon.
So, I’m going to talk a lot of differences between LED shop lights and grow lights. And then when we get into grow lights, we’re going to be talking about low wattage grow lights and the high wattage grow lights, and the advantages and disadvantages to both.
But before we get anywhere close to any recommendations, I want to talk about some of the things that you’re going to see and read and hear about, and are kind of important, but kind of not important, but you still should be familiar with these terms because you’re going to see them.
The first one is called PAR. It’s photosynthetic active radiation. And again, I’m going to get into the definitions later.
The next one is PPF, which is photosynthetic photon flux. And then there’s PPFD, which is photosynthetic photon flux density.
And then probably something’s going to be more common, and what we’re going to talk about a lot for the homeowner is just a simple term called kelvin.
It is sort of a temperature range, but it’s not like kelvin that you learned about in chemistry class, which is a real temperature. This is more of a color temperature, and we’re going to talk more about that.
So, let’s get into these terms.
And I’m going to tell you that they are important because they are, but I’m going to also tell you that they’re not important because they’re often misused. So, the first term is PAR, P-A-R, or photosynthetic active radiation. And this is the wavelengths of light that plants actually use. And they go from 400 nanometers up to 700 nanometers.
So, 400 nanometers is down towards altar violet, and 700 nanometers is up towards infrared, so blue at the lower ends, red at the higher ends. It’s very close to what the human eyes can see, actually. The human eyes can actually see from 380 to 700, so it’s pretty similar. However, plants will absorb more blue light than green light and more red light than blue light, but they still use green light even though they reflect it. So, don’t let the fact that these plants are green, that all that green light is being reflected… The plants are actually using some of that energy from the light. It’s just changing the way the green light bounces back at you. So, some of its absorb changes the color of the light, and then that’s what we see. Now, here’s where it can get confusing, because as I said, plants use more red light than blue light. But for the vegetation stage we don’t really need much red light.
However, it is still important to all plants and we should be really concerned about getting the full spectrum, the full par spectrum, from 400 nanometers to 700 nanometers, on our plants. So, we want all those photons. Now, photons are the smallest possible packet of electromagnetic radiation or light that the plants receive. So, photons is what we’re actually measuring when we’re going to measure all these. So, we’re measuring the wavelength of the photons is it’s hitting the plants. I know it seems confusing, and it’s, in a way, pertinent but not pertinent to what we’re talking about, but knowing these terms makes it easier to pick out a good light from a bad light. However, to measure power, you need a special meter. It’s a power meter, and they’re very expensive. A halfway decent one actually is five to $600.
The good ones are in the thousands. And there’s a lot of people and a lot of authors that give you these formulas to determine PAR from lumens and light candles and any other way that we can actually measure light inexpensively. And in reality, it’s not true. You really need… If you’re going to do this right, you really need a power meter to accurately measure how much useful light your plants are getting. And that’s just… For what we need to grow microgreens at home, that’s not important. If you have greenhouses, if you’re growing hundreds or thousands of trays of microgreens, then maybe it would be worthwhile. I’ve looked into them. I really want one because I just like gadgets, but it’s… Not even for what I’m doing, it’s not worth it to be buying a five or $600 PAR meter to figure out what our PAR rating is for our lights.
So, PAR is the wavelengths of light that plants use, and there are other things that we need to consider. And the next one is PPF, which is photosynthetic photon flux. So remember, a photon is the smallest measure of light, but we need to measure how many photons are actually reaching our plants. And that’s where this photosynthetic photon flux, PPF, comes into. And this definition is how much light and the power range is being produced by the light. So, it’s actually micromoles per second. How many micromoles of photons per second are reaching your plants. In a way, it’s intensity. So, what’s a micromole of photons? While micromole photons is 602 quad billion… Yes, that’s a real number, photons. 602 quad billion, with a B, photons in the power range that are reaching your plants. So again, it is intensity. So, that’s micromoles per second.
So, how many photons are hitting your plants each second, that’s what we’re measuring when we see PPF on any light box. However, as you know, light disperses, right? You have a point of light, it goes in 360 degrees. So, not all those photons that the light is putting out is hitting those plants equally along the distance of the tray. So, then we need to figure out the photon density, which is how many photons are actually hitting our plants per square meter. So, the photosynthetic photon flux density, PPFD, is how many photons are landing in a square meter per second on that tray. All these values are important to the plants. They don’t know it, but we figured out that that’s important to the plants. But if we can’t measure it cheaply, then why are they important to us?
Well, if we’re going to be buying high end lights, all those light manufacturers, we’ll put these numbers on the boxes. And you’re going to see all kinds of spectrograms and how the spectrograms change per distance from the light. There’s all kinds of calculations that go into this. And I think I will go more into it on a blog. It’d probably be a pretty boring blog, but I’m sort of nerdy like that and I like to include those things. So, I might make short little articles, sort of definition articles on all these, so that I can at least reference them at some point. But in the end, this is what’s important to the plants. This is how we measure what’s important to the plants, but we can’t really economically measure it unless you know we’re in business and making quite a bit of money. In a way, it’s important, and it’s important to know what these values are so that when we buy high end lights… And if you’re going to grow lettuces or a lot of microgreens, that could be important to you.
But most of us aren’t. We’re going to be buying less expensive lights. And here’s where the problem is. Inexpensive light manufacturers aren’t going to go to the trouble to measure all these values, because they know most consumers don’t know what they are, and they’re right. It’s important that we know what these terms are and how they’re used. But in the end, they’re not really important, because for the most lights we’re going to use, you’re not ever going to see these value. When we buy an inexpensive light, we’re going to get several numbers. So, we’re going to get wattage, which really isn’t important. That’s just how much power the light uses, has nothing to do with what goes to the plant, because there’s inefficiencies. So, we don’t know how inefficient the light is. And that’s where lumens coming, because lumen sort of measures the inefficiencies. So, we can say like, “Well, there’s this much power getting to the plants, but still it talks nothing about the wavelengths or the color of light, which is the wavelengths, that’s reaching the plants.
So, there is this other value called kelvin. Now, kelvin is usually given on any inexpensive light. Even shop lights, they talk about kelvin, because it’s the temperature of the light. It’s what we observe with our eyes. And if we can observe it with our eyes, so can the plants, because remember, our eyes pretty much see exactly what the plants use as far as wavelength. So, there’s this value called kelvin. And again it is a temperature of color. So, it’s a color temperature. It’s a scale color temperature. I guess that wasn’t very clear. So, kelvin, the measure of kelvin, is actually the scale of color temperature or the visual warmth characteristics of a light source. Is it the best way to choose a light for plants? Well, no, but it’s all we have, so that’s what we need to use. So our high end lights are going to give us all these other numbers, the PARs, the PPFs, the PPFDs, but inexpensive lights, for the most part, are just going to be giving us.
So, let’s talk a little bit about kelvin. Kelvin is sort of backwards to the wave length. So if you remember right, ultraviolet is the low numbers around 400, and infrared is the high numbers around 700 nanometers. Well, with kelvin, the lower numbers are more towards the red colors, and the higher numbers are more towards the blue colors. And really, for microgreens, we want a lot of the blue color. So, I’m sure most of us have gone to a store and bottle light bulb, and we’ve seen words like warm white, soft white, cool white, bright whites, daylight bulbs. This is what we’re actually talking about. So, let’s go over these different values. Let’s talk about the kelvin scale. The kelvin scale goes from really low near zero up to tens of thousands of kelvin, but we’re really concerned more about from 2,700 to 6,500. So, let’s go over those values.
So at the low end, at 2,700 kelvin, we’re talking about warm white light, actually has a lot of reds in it. At 3000, we have soft white. At 3,500 we have what they call neutral white. Around 4,100 kelvin, we have cool white light bulbs. At 5,000 kelvin, we have bright light, or basically full spectrum light. And at 6,500, we have what they call daylight. So, these are the values of kelvin that we’re most concerned about. And this is what we’re going to talk about a lot when we talk about lights for homeowners that want to grow mic greens, because these are the scales that we’re going to have. Now, if you want to buy a high end light, we’ll get into those, a grow light, if you will, we’ll get into those a little bit later, and I’ll give you some recommendations, but let’s talk about more about this kelvin scale right now.
So at the low end, below 3000, below 3,500, we have more red light wavelengths hitting the plants. Red light is important to plants, it produces biomass, it produces how hefty the plant is. However, plants grown under mostly red light, young plants growing mostly under red light are going to elongate. They’re going to grow really long. They’re going to stretch because they want more. They’re going to stretch towards that light, which is what we don’t want. We want more of the blue range, because it’s going to stop that stretching of elongation of the stems. We want more of the leaf biomass. And also, blue light has been found to increase more of the antioxidant levels than a lot of plants, especially like lettuces, or really all the leafy greens. We want lights to have more… We want light color, I should say, that is more in the blue type spectrums, which is the 5,000, the 6,500K values.
So, those the bright whites or the full spectrum or the daylight light bulbs, that’s what we want. That’s not to say that other lights won’t grow microgreens. For the first two years I grew microgreens, I grew them under a cheap LED Home Depot light, which was 4,000k, and the plants did wonderful. I guess looking back on it, maybe they did grow a little bit taller. They were a little more stretchy than the microgreens growing and the lights I’m using now. I’m not a hundred percent sure because I didn’t really compare them, but just thinking back. But still, those microgreens look good. They grew well. So, that was fine. However, I have found that microgreens grown under lights of at least 5,000 kelvin do really good overall for all different types of microgreens. So in summary of just this section, what is important? If you’re going to have a high powered grow light, you’re going to want to look for the PPFD, the photosynthetic photon flux density. That’s how many photons are reaching your plants in an area underneath the light. It’s a density. We want that.
Low end lights, low wattage lights, lights that you’re probably going to use for most microgreens, you’re going to look for that kelvin temperature. And you want any light that has a kelvin temperature above 5,000. 5,000 to 6,500 is what we’re looking for. So more to the point of probably why you’re listening to this podcast, should you buy grow lights or just LED shop lights? Well, the answer is it depends. And I’m going to tell you right now, it doesn’t really matter. I’m going to tell you about my experiences using both and why I think it doesn’t matter, but why most beginners should lean towards just the LED shop lights. Don’t worry about the grow lights. Just get an inexpensive shop light. The Barrinas are really excellent. If you don’t want to go through Amazon and buy those, then you can get any light at any hardware store that has a K value of 5,000 or more and you’re going to be fine.
So, let me talk a little bit more on why I think the low wattage lights, these shop lights are the way to go, because there’s a lot of benefits to low wattage light. One, they’re inexpensive, so you can actually get more point sources of light for the same amount of money. So, instead of having one light that shines really high and intense in the middle of your grow area and gets weaker at the inverse square, so every time the distance doubles, you’re losing four times the amount of light energy. So instead of having one light that’s really great in the middle, you can buy two or three or four, or sometimes up to 10 lights, if you want to get ridiculous, for the same amount of money that will have all different kinds of point light sources onto the plant.
So, it’s not shining straight down on the plant. It’s shining from all the different angles because you’ve got more light point sources. This gives you a more even distribution light, which is what we want. We don’t want light pointing in one spot. We want light coming from everywhere, and that’s what the advantages of a low power light is, is that we can put more lights on our shelves to get the microgreens light from all different angles. Another advantage to low wattage lights is that you can actually put the lights closer to the plants. They’re cooler. They run cooler. They’re not as hot. So, you can put that light closer to your microgreens, which means less light is escaping out, if you will, around the plant. So, if you have these high powered grow lights, say 100, 200, 300 Watts, whatever you have, you have to have those lights quite ways above the plant. So, there’s a lot of light that goes out and away from those microgreens that is doing nothing, any good except getting in your eyes.
So, having low powered lights let you keep daylight closer to the microgreens. So, are there advantages to high power grow lights? Yes, there is. Those are built specifically to grow plants. Som the light range, the power, if you will, of those lights… Well, actually not… The light spectrum of those lights is all into the PAR range. So, all the light energy that those lights are producing, all those photons are the exact wavelengths that plants need at some point in their life, while with low wattage lights, we really don’t know what the power rating is unless we have an expensive power meter. But again, that’s sort of overkill, unless you’re doing this for a living. I will say, however, that if you want to grow microgreens or lettuces to the baby leaf stage, that the high powered grow lights are actually a little bit better than any of the low powered shop lights that you can buy. So if you’re going to grow lettuces or spinach or mesclun, then you probably want to get into at least an SP150 Mars Hydro grow light.
One more important factor of using an LED shop light over a grow light is that the shop lights are pretty much set it and forget it. You put that shop light eight to 10 inches above the microgreens and you’re done. That’s it. They just grow microgreens. You may have to move the tray a little better, you may have to put something underneath the tray or raise it or lower, depending on what type of microgreens you’re growing, but you pretty much just set that light up. You put however many light you want to. You can’t really overheat the microgreens. And that’s it. You’re done. They grow microgreens. My experiences with grow lights is that there’s a lot of finagling that you have to do. Depending on the wattage, depending on what type of microgreen you’re going to grow, you really have to be careful, because those grow lights are a little bit more powerful. They put out more heat. You can’t have them as close. Microgreens grow different underneath the grow lights, and it’s just been a lot harder to find the right distance for different types of microgreens.
There’s a lot of trial and error to get this shelf height just right. It’s just much harder. I’ve also found that a lot of micro greens grown under grow lights that are too close, the leafs are a lot smaller, the microgreens are a little bit shorter. They’re very happy plants, don’t get me wrong, but you just don’t get the yield out them that you do under LED shop lights. So after all that, what are my recommendations? Well, my recommendations is that any light will work. It just takes time to dial it in. That said, most people, if they’re just growing micro greens should just go with an inexpensive or several inexpensive LED shop lights. Buy two or three, put them on a shelf, you’re going to be able to grow micro greens just as well as anyone with a high powered LED grow light. You can even get away growing a lot of lettuces under LED shop lights.
They’re not going to be as red colored as they will under a high powered grow light, but you’re still going to get away with a halfway decent tray of lettuce. If you want to grow a lot of lettuce, say for your family over the winter, and you want to grow three, four, five trays of baby leaf lettuce, then you probably will need a more high powered grow light. That’s just the facts of it. And I’m going to show you several. I have some experiments going on. I’m going to show you several this winter. I’m also experimenting with a Barrina grow light. It’s low wattage, but don’t hold me to this. I want to say it’s 24 watts, but they may be 40 watts. But they’re small, they’re two foot long, they have reflectors on them, and they fit on a nice small little bread rack, which is really handy, because you can put just bread rack about anywhere.
You can put it in a closet, you can put it in a hallway, and you can grow great micro greens and great trays of lettuce in a small little area. However, I still have had to finagle around with the shelf height. I’ve had some problems with it, getting the micro greens getting up close and too hot. I’ve had small leafs instead of regular size leafs because the lights were too close. So, it’s taken me a while to adjust the shelves to where I want them. But again, that’s just trial and error. It’s just if you grow a tray and the leafs are really small and not what you want, then you just lower the shelf. I mean, it is just a little bit of finagling, but it’s unlike the LED shop lights where you put them on there, you put the tray about eight inches, 10 inches below the lights and they’re just going to work.
You may ask about nutritional value. Well, I really have no idea. I have no way to measure nutritional value, and I always have problems with any of the labs that are measuring nutritional value or any person or company that’s stating nutritional value because I think it really changes batch to batch. I just can’t see how if you grow kale microgreens in point A, and then another tray in point B, that they’re going to have the same nutritional value. They’re going to have different soils, different lights, different temperatures. I don’t see how you can really compare them. I still think that microgreens have a lot of nutritional value, and it’s just a matter of eating enough micro greens and enough variety to get the vitamins and minerals and antioxidants and whatever other health benefits they have to you. So, it’s like anything in any diet. It’s just eat a wide variety in a reasonable amount, and you’re going to get the nutritional values, whether they’re under LED high powered grow lights or whether they’re under LED Shop lights bought in from Home Depot.
So until I edit this, I’m not really sure how clear I am, but here are my recommendations. Most people should just be buying LED shop lights. The Barrina brand is really good. I’ll put a link down below. The LED grow lights, the low wattage grow lights seem to be very good. There’s a little bit more finagling to get the right height, but they seem to be growing really well. And if you want to grow lettuces, like red leaf lettuce, like the ruby red lettuce, then you really should get like a Mars Hydro SP 150 for one or two trays. If you want to go to four trays, the Mars Hydro TSL 2000, it’s either TSL or TLS 2000, grows four trays on a two by four foot platform that I have really well.
There are other brands that I’m trying, but so far the Mars Hydro and the Barrina brands are the ones that I do recommend. Again, links to those will be down below. I’ll put all of my other links to lights in the show notes. And the show notes for this are at homemicrogreens.com/ 026. That is the episode number, episode 26. So for any episode, you can always just put into three digit number. Zero’s a placeholder currently. So if you want to listen to podcast 15, it’d be 015. So, this one is 026, homemicrogreens.com/026, and I’ll have everything linked up.
And if I add more podcasts or more articles on lights, I’ll, again, go back and revise all these articles, all these show notes so that all the links will be there. I hope you found this useful. And again, people seem to make a big deal about lights. I don’t really think it’s that important. I think if you have a light source, you’re good to go. I think there are other more important things like the soils or whatever additives you’re using. If you’re not using a good soil, it’s more important to microgreens than what light you use. I hope you have a great rest of your week, and we’ll see you in the next episode.