Indoor marijuana growers have several grow op challenges, and perhaps the most important is what to use as an “indoor sun.”

Until LED grow lights came on the scene, almost all growers used high intensity discharge (HID) metal halide and high pressure sodium grow lights. HID bulbs were originally made for street lighting, store lighting and other non-horticultural purposes.

A few HID manufacturers claim to now be making HID bulbs with spectrums themed for marijuana’s light spectrum needs, but that doesn’t mean HID is the best choice for indoor grow rooms. Why? Because HID bulbs are energy wasters, too hot, and wear out fast. They generate huge amounts of heat that cost you big money in extra air conditioning expense, and can burn or stunt plants and buds. They can also burn you.

Plus, HID bulbs don’t have the ideal spectral output for cannabis, and you can’t adjust their spectral output like you can do with some LED grow light brands.

HID deficiencies are why more and more growers are switching to light-emitting diode (LED) grow lights. LED grow lights have many advantages over HID, including less heat, better electricity-to-light conversion ratios, longer unit life, adjustable spectrums, and reduced energy costs.

Avoiding Common LED Grow Lights Mistakes

The Growing Marijuana Perfectly team has eagerly embraced LED grow lights as many cannabis growers have. We’ve tested many of the major brands (whose top units usually cost at least $1400 if not much more) and many minor brands too. Unfortunately, our conclusion is that a significant percentage of LED grow light brands are a rip-off in one way or the other, and that using LED grow lights requires you to make careful, specific adjustments in how you grow your plants.

Want to avoid common LED grow lights mistakes and get the most bud weight and potency from your LEDs? Great, and here’s what you need to know about LED grow lights…

First of all, many LED manufacturers make impressive-sounding product claims, but don’t have third-party, legitimate side-by-side marijuana grow op testing to prove their claims.

For example, some claim their lights equal or even outperform other LED brands and HID grow lights (including double-ended bulbs) in harvest weight and cannabinoid/terpenoid percentages. But you rarely see definitive proof of these claims verified by scientific testing and third-party certification.

Our research shows that only the most skilled growers using the right makes and models of LED grow lights routinely get harvest weight and potency equaling or exceeding what you get with high pressure sodium (especially double-ended HPS).

Another challenge using LED grow lights is you must adjust several feeding and environmental factors to accommodate LED grow lights’ effects on your marijuana plants, and there’s a learning curve involved, it’s not one size fits all.

You have to be more attentive to your plants, realizing that every marijuana strain has its own way of handling grow light spectrum and intensity.

Using LEDs, you may want to have your room be a few degrees warmer than usual, and add extra calcium and magnesium to your feed program, especially in bloom phase.

Growers are familiar with Cal-Mag supplements already. Use a 50% reduced dose intermittently during grow phase, and every other watering during bloom phase if you’re running a high-PPFD LED grow light program.

You also pay closer attention to the amount of water and nutrients you give your plants because some LED lights increase water use by about 40%. We reduce the parts per million of our feed program in those scenarios, because running more water means running more nutrients, and that can cause nutrients burn and lockout.

You’ve also got to make very sure that your nutrients pH is absolutely correct. You need accurate pH and TDS meters, for sure.

If you’re running the very best LED grow lights, add C02 to your grow room air during lights-on to maximize the increased photosynthesis your lights are giving you.

Grow phase C02 should be around 650; bloom phase C02 should be from 700-1100 parts per million.


One common problem you see with LED grow lights is light burn, sometimes called leaf bleaching. Take a look at the photo above. That’s LED leaf burn.

Your plants’ leaves, especially those in the top third of the canopy, become bleached out, turning a pale yellow and often becoming crispy, although the leaf veins stay green.

This bleaching problem is confusing because it can easily be misdiagnosed as a nutrients problem, leading to nutrients dosing mistakes and other hassles.

Bleaching interferes with photosynthesis and other metabolic processes, and can sabotage plant growth, structure, potency, and harvest weight.

Most LED grow light manufacturers give you canopy-to-light distances that are way closer than you can actually safely use—because they don’t want to scare you away from buying their gear, especially when you’re growing SCROG or in limited vertical height gardens.

And when I say “limited vertical height,” I’m talking about grow rooms with 7-8 foot ceilings, which is what most home marijuana growers have.

Using the most powerful LED grow light models from most major LED manufacturers, we’ve had to put the lights at least 20-30 inches away from the canopy to reduce bleaching. These are the powerful models that manufacturer’s advertisements claim will replace a 600-1000-watt HID light.

So using one of these high-powered LED lights in grow room with eight-foot ceilings, you’ve already lost three feet or more of grow height due to worries about bleaching– meaning your plants can’t be more than five feet tall, and that doesn’t include the inches you lose due to light stands, light movers and hangers.

The sad fact is, some LED grow lights are just as bad as double-ended HID when it comes to canopy burn and how high you have to have them above the canopy.

Even using LED grow lights that allow adjustable spectrum and intensity, we’ve still seen bleaching after dialing down the intensity by 50%. Experts we’ve spoken to say the bleaching isn’t due to intensity alone, it’s also due to the manufacturer choosing the wrong spectral output for their grow lights.

Another problem is some LED grow lights manufacturers overestimate their lights’ “footprints.” The light footprint is how much of your grow room canopy the light is alleged to provide adequate light for. We’ve tested lights that manufacturers said provide adequate photon intensity for 16 square feet, but the actual coverage was 10-15 square feet.

Some manufacturers give differential coverage estimates for grow and bloom phase, but what we’ve experienced in multiple grows with different brands of LED is that coverage estimates are often about 5-40% too generous.

Serious marijuana growers should get hold of quality meters that accurately measure photon flux density (PFD) in the photosynthetically active radiation (PAR) range.

The most reliable meters for LED grow lights are made by Apogee. Using these monitors, you monitor the amount of photons reaching your plants, and see the photon distribution pattern which helps you place your plants for optimal photon dosing.

Another hassle for LED grow light users is getting useful technical support and warranty repair and replacement. Many LED grow light manufacturers treat growers disrespectfully.

For example, here’s a typical complaint posted online about Fluence Bioengineering, an Austin, Texas LED grow lights maker that’s one of the so-called “most respected” LED grow light manufacturers:

“Fluence customer service is non-existent. If you do get ahold of someone they say they will call you back with info but never do. After 5 calls, over an hour on hold and a 40$ long distance charge I was finally able to order a light. Asked the sales guy how long it takes until they ship and he said about a week after payment is cleared. Took a week to clear payment and two weeks after cleared payment I called to see if it was shipped and they said it will take another 15 days until they will ship it. I have now been waiting almost 2 months. If you do order a light don’t expect it any time soon. Can’t imagine what it would be like to try and get warranty or if you wanted to order multiple lights.”

This is just one of many negative reviews about Fluence, and it doesn’t surprise us, because when we had problems with Fluence grow lights and contacted the company, it was impossible to reach Fluence tech support, customer service or management.

Fluence is reportedly owned by Osram, reputed to be the manufacturer of premium LED chips. Too bad Osram is an unfriendly corporation totally uncooperative and lacking transparency when it comes to responding to grower queries and media queries. This kind of rude stonewalling is also with seen with some other LED manufacturers.

Companies like Fluence ought to realize that Chinese LED grow light and Osram LED chip counterfeiters are coming for them soon. We used black-market backchannels to procure Chinese-made LED grow light counterfeits that technically appeared to be the exact same as the lights they were copying. The Chinese even claim to have figured out a way to duplicate Osram and Cree LED chips (Osram and Cree are the purported top-rank LED chips).

These Chinese units cost at least 40% less than the original brand’s units they’ve duplicated, and seem to perform just as well. Problem is, when these units go bad, the Chinese seller isn’t available for tech support or warranties.

We could go on and on about the nuances of different LED grow light design, purposing, warranties, pricing, and performance. When you start trying to understand these nuances, you quickly discover that it’s a technical rabbit hole you go down and you might never come out again.

To make things simpler for you, our team has agreed that we can vouch for the integrity of at least three LED manufacturers. We’ve personally tested lights from two of the three, and have interviewed all three. We’re constantly testing new grow light brands, and will update you when we have more brands to recommend.

One company we have faith in is California Lightworks. Their CLW 1100 and 550 models are used in dozens of profitable commercial grow ops, and the 550 is especially popular in home grow ops. Their technical support and warranty people are timely, honest and professional.

Another company we recommend is Lush Lighting. Lush owner Matt Johnson is an honest, and super-intelligent guy who spent years researching photons, electrical engineering, grow lights, and cannabis photochemisty before he designed his grow lights.

When you talk to Matt about why his lights outperform brands that cost more and are better-known, he launches into a lengthy discourse about xanthophyll, carotenes, phycobilin proteins, photon flux, and other complex topics.

I don’t pretend to understand all the science he explains, but I trust his expertise because his lights have consistently been the most useful LED grow lights in my grow ops.

We’ve found that although Lush LED grow lights produce slightly less harvest weight in competition with HID (including double-ended bulbs), they produce 10-15% more cannabinoids and terpenoids, and you save several days off of each season because your cannabis plants grow and mature faster.

So when you calculate the total long-term cost of buying his LED light and running it versus running HID lights and replacing bulbs every season or two, Lush grow lights are a far better investment than HID grow lights.

As regards leaf bleaching and the evils associated with it, Matt sent us convenient three-dimensionalized charts that show exactly how many photons are reaching plants at various grow light heights above the canopy.

We’ve used his lights that replace 1000-watt HID at close as 16-24 inches from the canopy with no burning, bleaching or heat stress. Here’s an example of a Lush chart…

Dominator 2xXL high intensity Lush Lighting LED Agriculture  Grow Light.jpegAnd here’s a caution—you can’t trust most of those online “LED grow light review sites.” Notice these sites say little or nothing about harvest weight, cannabinoid and terpenoid percentages, strains grown, what they competed the test LED model against, and other relevant details.

They don’t show marijuana grow op photos of their alleged LED grow light test, and I don’t think these reviewers are actually using the lights to grow marijuana, if they used them at all!

Frankly, most of those so-called reviews are covert paid advertorials rather than an honest marijuana grow room evaluation of how the reviewed light actually works for cannabis growers.

Those review sites are often in business with the LED manufacturers, even to the extent of blatantly trying to sell the reviewed grow light at the end of the article. I don’t trust any of them!

LED Grow Lights: Ask Before You Buy

Premium LED grow lights that can replace 600/1000-watt HID grow lights cost at least $1400 if not much more. Before you buy an LED grow light, do your due diligence and make sure you know exactly how the light will work for you, and every little thing you need to know about distance from canopy, heat, warranty, repairs, and other details.

Sometimes I still use one or two HID grow lights along with LED, but only during the coldest winter months. Unless I’m doing grow light testing of other LED brands, I use only the Lush LED, and get great results. Other growers in our magazine consortium do the same.

If you’re looking to get your first LED grow light, already have one and are having problems, or want more LED lights, contact the manufacturer immediately. Anonymously explain to them the height, air conditioning, strains and other configuration basics of your indoor grow op, and ask these questions:

  • How far from the plants does the light have to be for seedlings/clones, grow phase, and bloom phase?
  • How much PFD (photon flux density) will the light deliver at various distances, and what is the recommended PFD for young seedlings and clones, established grow phase plants, and bloom phase plants?
  • What is a conservative estimate of the actual square feet of grow space that can be adequately lit by the lights you’re considering?
  • What spectrum does the light put out and why was that spectrum chosen?
  • How much actual electricity consumption does the light require?
  • Does the light contain Osram or Cree chips, which are the industry standard, rather than inferior chips?
  • Was the light spectrum researched for and tuned specifically for cannabis plants?
  • Can this light be used from start to finish?
  • What warranty, customer support and other assurance policies are in place?
  • How long has the manufacturer been in business?

Be sure to look at online reviews of the manufacturer and lights, but not from online review sites. Instead, look on grower forums, Google reviews, Amazon reviews and other places where reviews are more likely to be authentic rather than just coming from paid shills.

And pay attention to how friendly, honest, and helpful manufacturers are when you ask for information. If you email or call an LED manufacturer and it takes them forever to get back to you, or they don’t provide comprehensive, useful information, take that as a sign that you don’t want to do business with them.

Problems with manufactured LED grow lights have led some growers to start making their own. According to my grower friends who’ve made LEDs, it’s not all that hard to do, saves you tons of money, and gives you the opportunity to customize your lights to exactly match your grow space and growing style. Several LED-maker websites and forums can be found online, including this LED self-manufacture forum.

In summary, the best LED grow lights use far less electricity and generate much less heat than HID, and last far longer than HID units. Used correctly, they can provide yields nearly equal to HID, but at a much lower cost.

If you find or can build an LED grow light make and model that works well for your grow room, it will be much better for your plants and profits than using HID. Now that you’ve read this article, you’re set up to know what questions to ask and what you’re getting into when you buy an LED grow light.

When you look at that dense, frosty bud grown under Lush LED grow lights (shown in the main photo for the article), you see what LED lights can do if they’re the right lights! LED grow lights are the wave of the future.

If quality manufacturers keep on pushing innovations, efficiency, spectral specificity and garden success, HID grow lights could be a thing of the past within ten years.