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Growing Cannabis with LED Lights - Pros and Cons

Created by
JoshuaHolt JoshuaHolt
Added 16 September 2020

LEDs Can Produce Decent Yields

Lighting is a necessary part of any indoor grow operation but is often expensive and a pain to maintain. Many growers have started switching to LED lights because of their low energy usage. But are LED lights worth it? This article goes over some of the pros and cons of using LEDs.

LED lighting has been around for quite some time now, but has only really become popular in recent years. The technology has developed much further, allowing for huge improvements in many indoor grow rooms. Whereas before LEDs were inefficient and not worth their cost, now they have the power and efficiency to provide exactly what is needed for a cannabis garden to produce a top quality harvest.

What Are LED Grow Lights?

LED (light emitting diode) lights work with a microchip to send electrical current to different diodes in a series. When the current passes through the diode it illuminates and creates what we see as visible light. In LED grow technology, the diodes are emitting specific visible colours that are essential for healthy plant growth.

The spectrum emitted by an LED grow light is not always the same and varies depending on what the LED is designed for. For cannabis cultivation we only really need two different colours, blue for vegetation, and red for flowering.

Blue Spectra For Vegetation, Red Spectra For Flowering Or Full Spectrum For Whole Cycle

There are some types of LED light that have a full colour spectrum which can be used for the whole life cycle of a cannabis plant. Although it is not essential to give a plant the full spectrum, adding more colours can improve the plant's understanding of its own environment because the LEDs emit a closer representation of sunlight.

Are LED Lights Better Than HID lamps?

HID (high intensity discharge) are the most commonly used types of grow light and they serve their purpose well. However, there are some drawbacks to using them, especially now we have newer technology developing at the forefront of the industry.

The main problem with HID lights is their high energy usage. Although HID lights are usually more efficient in the amount of lumens they provide per watt, there are other aspects to consider which make the overall efficiency better in an LED light.

LEDs do not use ballasts, which are needed in HID lighting to convert the electrical current into usable energy. This means they lose efficiency over time and eventually need to be replaced. LEDs do not need this extra equipment to do their job and can be plugged straight into the mains.

HID Lights Use More Equipment Than LEDs

LEDs do not last forever but they have more than double the life span of HIDs. The filament in an HID lamp is very delicate and loses its intensity quite rapidly after use. HID bulbs are also broken easily if it not handled with care. Plus, HID lamps contain harmful elements like gases and mercury, making LED lights a much safer option overall.

Another factor that makes LEDs better is less wasted light. This is mainly because they can be placed closer to plants but also due to light being directed in a much more efficient manner. LED lights are already directed so they do not need a reflector like HIDs do.

HIDs run at very high temperatures and need cooling equipment to ventilate the hot air they produce.

In terms of yield and quality, LEDs are now as good if not better than HIDs. It all depends on the set up and how a garden is managed. LED grow lights have given growers the possibility to further fine tune the accuracy of their growing environment, so plants can now receive the exact light they need, exactly when they need it.

Tip: Having the extra warmth from HIDs can be useful if you are growing in colder climates.

Pros of Growing Cannabis with LED Lights

If you are planning to grow with LEDs, it is important to understand the pros and cons so you know if it is worth it for you. Unless you have a high budget, LED lights may not the best solution because the cheaper ones are often not on par with what they should be.

  • They do not produce too much heat - Less equipment needed to maintain grow room conditions.

  • Energy efficient - LEDs are almost 50% more efficient than HIDs.

  • Direct light - Concentrated light dispersion so plants use photons more effectively.

  • Environmentally friendly - Does not need replacing as often.

  • Last longer - A good quality LED grow light lasts at least 50000 hours!

  • Safe - Less heat/harmful materials, no breakable filament, and protected in housing.

Industrial Sized LED Cannabis Grow

Cons of Growing Cannabis with LED Lights

Although LEDs sound great there are a few drawbacks to consider before going ahead and buying them.

  • LEDs are difficult to replace - if one LED breaks you may have to send the whole light back to the manufacturer.

  • Expensive - we recommended choosing high quality to get the best results. Cheap LED grow lights are not worth it, often leaving you with small plants and low yields.

  • Light can be too intense for plants - it is possible to burn your plants with light. Leaves can become discoloured or brown, curl and dry.

LED Light Grow Tips

Cannabis plants need around 30 - 50w per square foot of grow space. The amount of light plants need depends on which stage of growth they are at. This can be adjusted either through using dimmable LED lights or by simply moving lights closer to plants over time.

LED Lights Can Be Placed Close To Plants

Seedlings - Seedlings should be introduced to the light gradually, especially if it is a high output LED light. An intense light can be a shock for a young seedling, so it is a good idea to start with your light about 50 - 60cm away from the tops of your plants and lower it 2 - 3cm per day. Set the light to vegging mode (blue) if it has one so the light can be closer to the plants.

Vegetation - If you notice plants stretching too much, think about lowering the light or increasing the intensity. This usually happens because plants are not receiving enough light. LED lights should be on for 18 - 24 hours per day and follow the same schedule as regular grow lights.

Flowering - Full spectrum LED exposure is recommended for the flowering phase. It is possible to only use red spectra LEDs but plants grow better with all colours available. Lights should be at their most intense by this stage so either move lights closer to plants or turn up the intensity to full. The closest distance lights can be from plants depends on the strength of the light.

Example LED Grow Room Setup

LEDs should not be placed too close to the tops of your plants. Check the manufacturer information as LED lights vary in intensity. You may use the following table as a simple guide, but bear in mind that these are rough estimates that depend a lot on the quality of LED light you purchase. 

LED wattageDistance from canopyCoverage(feet)HID equivalent
125 - 150w30 - 40 cm2 x 2200 - 300w
150 - 250w40 - 50 cm2 x 3300 - 450w
250 - 400w50 - 70 cm3 x 3450 - 600w
400 - 600w70 - 100 cm4 x 4600 - 1000w

Conclusion

If you have been doubtful about LED lights then hopefully this article will have cleared things up for you. It is true that until recently, LEDs were not up to the same standard as HID lights in terms of their efficiency and productivity.

Finally LEDs have reached a level that makes them an affordable, viable option for home growers. There is so much to be learnt about LEDs, so share your thoughts with us in the comments section below!

External References

LED Lighting Affects The Composition And Biological Activity Of Cannabis Sativa Secondary Metabolites. Industrial Crops and Products. - Namdar, Dvory & Charuvi, Dana & Ajjampura, Vinayaka & Mazuz, Moran & Ion, Aurel & Kamara, Itzhak & Koltai, Hinanit. (2019) 

Basics of LEDs for Plant Cultivation. - Fujiwara, Kazuhiro. (2016)

This article was updated September 2020.






Comments

NuggetPawn
NuggetPawn

Yeah, I don’t wanna shit on who ever wrote this as it’s well written and laid out, but unfortunately it’s mostly not accurate and or is misleading, which seems to be the story with a lot of online canna info these days :disappointed:

Some points below (Edit: I wrote most of below pretty quickly and apologise in advance if I missed any small details):

•1
Lumens or lux is not a metric for measurable light utilised by plants, as the human eye is more sensitive to green light by several orders of magnitude vs red/blue which lux meters account for. PAR is the metric for plants (photosynthetic active radiation), which adds up all the umols of lightwaves between 400 and 700nm.

•2
While LED’s do not have traditional ballasts, they do have drivers to convert current from AC to D.C. Not quite plug and play like the author says.

•3
Stating that an LED fixture is better due to ‘less wasted light’ as it is closer to the canopy is only half the story. Reflection losses are definitely a factor which changes depending on the material you chose to line your grow room walls with. However the stand out best reason for LED is the fact that the spread of PPFD (Photon Synthetic Flux Density) is much much more even. Without CO2 supplementation cannabis can usually handle up to 1000 PAR before showing signs of stress. Because the light is more spread, this allows growers to get great coverage to the edges of the tent as well as the middle, unlike HID, where in order to not burn your plants, you may have 1000 PAR in the centre but only 300-400 PAR on the edges, thus increasing reflective losses (as the photon has more opportunity to bounce off of walls/floors etc). It is also important to note that not ALL LED’s are good at spreading light, COB vs bar style lights for example have huge differences in PPFD footprints. Bar style LED’s are currently the best widely used light delivery method on the market today.

•4
‘In terms of yield and quality, LED’s are now as good if not better than HID’s’

Again, this is a very vague representation of the facts. Depending on the LED, some are in fact twice as efficient and can therefore produce up to 2 times more yield per watt of power used vs traditional HID/HPS. HOWEVER, some LED’s like a lot of the blurple type fixtures with fans/large heat sinks actually produce less light per watt than HID/HPS.

•5
‘LED’s are almost 50% more efficient than HIDs’

Not true, as mentioned in last paragraph, some lights are only 80% as efficient as HID, others are over 100% more efficient which I am more than happy to link models that are.

•6
‘Cannabis plants need around 30-40w per square foot of grow space’

After the points I have made in 4 & 5 it is becoming clear that you can not use watts as a metric for light delivery per square foot due to the fact there is huge parity between the best and the worst LED’s on the market. Looking at PPFD charts from reputable LED companies is the best way for a grower to judge how well a fixture suits their grow space. As a rule of thumb, flowering plants need at least 500 PAR to grow properly. 700 - 1000 PAR is optimum and growers buying new lights should try to find lights that achieve close to these numbers across the grow space they have. If an LED company does not provide a PAR map, I would be dubious about buying from them as if they understand the science, they would know this is very important information.

•7 ‘For cannabis cultivation, we only need two different colours, blue for veg and red for flowering’

This is a myth, which stems from the HID vs HPS days. Light colour and spectrum only affects plant morphology, not yield or quality. The reason why people used to choose HID for veg was due to the bluer light making stockier, shorter plants. HPS lights are chosen for flowering because they’re MORE efficient than HID. HPS is 10-15% more efficient than HID and therefore confirmed people’s beliefs that it was the red spectra that was beneficial when it was actually the amount of usable light per watt the fixture delivered.

Bluer spectrum lights lead the plant to believe it is growing in an open area with little competition for light, as the blue concentrations of light without any shade are higher than in shade. This leads the plant to grow shorter simply because it doesn’t need to outperform any other plants. It is important to note that blue light does not penetrate leaves as deeply as green and red.

Redder spectrum light causes the plant to believe it is growing in shade, this is because red light penetrates through leaves much better than blue.

Thought experiment:

Think of a cannabis plant growing underneath a canopy of trees, as the light comes down and hits most of the leaves on the tree just above, those leaves act as a filter, holding onto most of the blue and passing some of the red, by the time the light hits the cannabis plant the sore trim shifts heavily towards the red, this indicates the plant to bush out in order to increase its chances of growing into direct sunlight.

This is a good video about light spectrum and it’s affects on plant growth: https://youtu.be/oK8e5bgqgT8

I could continue to go into greater detail but I am pretty sure most people will not read this far. Again, the layout and the presentation of this article is spot on, but the information is not, with GD being a great platform for growers, at the very least the published information on this site should be as accurate as possible. If you would like to discuss further/develop a new article I am more than happy to help, otherwise I suggest you take this down before more unsuspecting growers receive poor information.

Thanks,
Nug

Show all replies (7)
NuggetPawn
NuggetPawn

@jedh484,
I appreciate your honest reply, and also understand that you may not want to over complicate the article, like I said before, if you’d like help reworking it, pm me and I’ll give you a few ideas/sources :+1:

JHGD420
JHGD420

@NuggetPawn, Thank you for the constructive feedback, I appreciate you taking the time to outline all the points you mentioned. I will see what I can do to make an edit on the article when I have time. I would have liked it to focus more on the pros and cons rather than the technicalities behind LEDS. And my apologies for the misleading info, perhaps it was rushed to get it in by the deadline and I didn't verify the info before publishing. Thank you once again and happy growing :)

NileGrower
NileGrower

@NuggetPawn, good information thank you I read till the end ;)

ujekg
ujekg

PERSON WHO WROTE IT HAS NO CLUE..........................................FEELS LIKE 4 YEAR OLD INFO

https://fluence.science/wp-content/uploads/2018/11/Fluence-Photobiology-Guide-2019.pdf

Clutch
Clutch

Is Josh even real? :grin: I clicked on his Pic and got stuck loading the profile. No offense just checking.

DrWeird
DrWeird

@Clutch, It's weird b/c I've blocked him before they made his profile go blank and he still shows up in my Grower Network.

Definitely is starting to make me concerned about privacy and security if you can't even block people.

Clutch
Clutch

And yet another one as a notification :face_with_rolling_eyes:
Just make this a journal update Grow Diaries.

Uk420Show
Uk420Show

Hmmmm I think I'll Just say No comment to this. I love this site but can this guys post's stop getting through, I mean 20 ppl in the comment section could right a better article, I bet a year of my salary on it !

Justa_Retard
Justa_Retard

Yoo @NobodysBuds.. I don't think you're gonna win the copywriting contest.. They prefer this halfassed garbage, over your math. lol

Show all replies (6)
GreenHouseLab
GreenHouseLab

@NobodysBuds, well said :left-facing_fist:

Justa_Retard
Justa_Retard

@NobodysBuds,

Don't think you can call it history, since it's just me making fun of his credibillity, resulting in him using the block button. lmao.

NobodysBuds
NobodysBuds

@Justa_Retard, bwahaha

okay, so there is some history between you two. I'll get the popcorn.

BlackListed
BlackListed

why do i get these missleading articles daily now ?! i am totaly baffled as what this website has become....this is a place where ppl pay and force others to get notified for stuff which maybe LOTS OF THE PEOPLE here dont want to see or get notified about ....this is totaly out of hand and i think we should complain about to this towards @growdiaries ,aye?
*** for those who cant see @joshuaholt it is simply because he blocked us,he in my own opinion doesn't have a single clue about how to properly write an article and if someone takes his advice he can get burned for lots of time and money lost! stop posting this kind of stuff that can hurt other growers who barley start in this and maybe have some decent money to invest.....jeez !

BlackListed
BlackListed

@NuggetPawn,umm...2-3 days ago when i called him out i could see his profile :))) now i cant

NuggetPawn
NuggetPawn

@BlackListed, I don’t think he’s blocked anyone as I couldn’t see his profile before I made the comment, probably a GD employee if I was to guess

Weedeater
Weedeater

Where's the love for quantum board ? Are we back in time ?

TreeFarmerCharlie
TreeFarmerCharlie

This has a lot of misinformation in it. Also, why am I getting notifications for all these journal entries all of a sudden?

Tripledrop
Tripledrop

@TreeFarmerCharlie, I agree on your second point (and first point). GDs should add an “articles” section where these get posted to, and remove notifications when they get posted there. Stay safe, stay lit :fire: :grimacing::rainbow:

Secretflower
Secretflower

Hello, you say that LED lamps do not need ballast as for HID lamps, and all LED lamps have a driver that transforms the regulated DC current to have a lot of amperes, usually the driver is on the lamp itself, voila, I wanted to tell you about your mistake, peace.. :seedling:

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