by Callie

LED Grow Lighting = Half The Harvest

If you follow indoor gardening news regularly, you see a new micro garden gadget hit the scene quite often, and almost every one of them uses LED grow lighting. They call this green and sustainable, because it uses less energy, and somehow the marketing material always manages to convey your electricity bill savings will be big. There are three things wrong with this scenario:

  • It sounds efficient, but reality and marketing are opposites.
  • Harvest size and  growth rate is not included.
  • You can only expect to get out of a garden what you put into it.

When you go to the store to buy the ingredients for salad, your purchasing decisions are largely guided by price. You look for quality produce that is still plump and juicy, free of bad spots, and next you look at the cost. If you can get nice looking tomatoes, lettuce, and cucumbers for less without sacrificing quality, you’ll always buy the cheaper ones. It’s okay, you’re human, and you’ve got bills to pay. But you can’t apply this same kind of reasoning to everything in life, and plant growing is one of them.

I would venture to guess that for most people who want to grow food in their house, the first crop that ignites the bug is tomatoes, because off-season tomatoes are both over-priced, and generally lacking in flavor. If it’s not that, then its peppers. Both of these are fruiting plants, and to produce a fruit it takes an incredible amount of energy. You might liken it to child-bearing, and indeed, that’s the reason the plant develops fruits – to procreate. It’s just a seed pod! Be it ever so delightful to us humans, its a sack carrying the next generation of it’s species.

Pregnant women are constantly hungry, even if you’re a guy and unmarried, this is very common knowledge among humans. Fruit bearing plants are pregnant plants, and if they don’t get the fuel they need to grow those pods… well things can get pretty ugly. The best case scenario is your plants in the flowering stage with insufficient fuel look pretty nackered – all strung out, their hair falling out by the handful, yellow around the gills – and if they could snarl at you, cuss a blue streak, and toss you out on your ear – they probably would. But unlike a pregnant woman, plants are at YOUR mercy, and if you don’t fulfill their needs, you will simply get a pitiful harvest, if any harvest at all. So, your first job as an indoor gardener is to provide them with enough to eat, and it’s not from the fertilizer. It’s from the light energy you give them, which allows the plant to turn the nutrients into food.

Back To This LED Obsession

If all you want to do is grow some lettuce, an LED is your friend. It doesn’t even have to be big, unless you want to grow more than 2-3 lettuces at a time. A sleek little counter garden the length of a loaf of bread with a 65 watt LED grow light will pump out some lovely lettuce, but don’t even think about anything with fruits, that’s just a waste of time, space, and money.

Not all the exciting new hydroponic or aquaponic micro gardens use LEDs, I’ve seen a couple that employ CFL (compact fluorescent lamp). Sadly, here too, the lamp is low wattage, which translates to low energy plants are your best crops. You can’t grow a bumper crop of chili peppers or cherry tomatoes using only 150 watts of light energy. You can upgrade your selection to include some herbs though, but not cilantro – it’s going to be trouble under powerful lights, and if all it has is weak light – don’t even plant the seed. You’ll just be a plant murderer. It is such a temperamental plant, and definitely demands the real SUN. In a winter greenhouse perhaps, but not inside your house. It ain’t gonna happen.

What About 200 Watt LEDs?

Now, you’re getting closer, but it’s unlikely you’ll find that your space, time, and money invested translates into something you’d view as efficient. Why bother with LEDs when you can get the same amount of light energy from a 4-lamp 4-foot HO T5 fluorescent fixture? And it will cost less to purchase than a truly good LED equivalent. I use one to start seeds for the outdoor garden, and when its close to time to move them outdoors, the tomatoes and peppers are definitely hungry for more light energy than this. They’re already starting to flower, which is good to get a solid start outside, but not if they have to remain under insufficient light their whole life. Switching to red lamps might increase flowering, but the plants themselves need more light energy! The most efficient move at this point is to move them to real sunshine, and if that’s not possible, buy a stronger grow light.

Here’s the best way to show you just how wrong people’s misconceptions about how much money they save growing under LEDs as opposed to high intensity grow lights. You get half the plant mass, and half the fruit, while saving only a few bucks/pounds over 3 months. Half the food from 3/4s of the energy use is not efficient! It’s not very sustainable either.

Someday, it might be possible to grow efficient food crops using LEDs as the main light energy source, and do so without needing a loan to buy the fixture. But that’s not the scenario today. LEDs are great as auxiliary lighting in the indoor garden. They’re awesome at growing leafy greens, but if you want more from your indoor garden, you’ve got to give it a lot more light intensity.

Need more details? Ready to learn more of what it takes to grow your own food indoors successfully, and efficiently? Read the print issues of Garden Culture Magazine.

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  • Theo Tekstra says:

    Oh dear here I find myself defending LED 🙂

    I don’t think it is as bad as portrayed here and we have come a long way since the referred test. The best horticultural LEDs now output 2.6 umol per Watt, and from that point of view the really good LEDs already outshine the HPS in certain spectrums. There are still issues of course, being the investment and the absence of heat in the light, which in many cases needs to be compensated by heating. It requires a different nutrients regime, so there is a learning curve too.

    • Callie says:

      Hi Theo,

      Thanks for bringing us up to date on the state of LED grow lights. Can you share a few more details? It would be great to know what are the best horticultural LEDs – what brand and which fixtures actually give plants enough umols to outshine HPS? Also, which spectrums do they deliver the better output in? I suspect that we’re still looking at prices that require a mortgage for the average urban gardener. Still it would be nice to know some further facts here, because as you know, every brand of anything claims its the best by far.

      I’m sure you can enlighten us to what is hype and what is not here 😉


Only strangers knock on the door at Callie's house. People who know her don't bother if the sun is shining - they know to look in the garden.