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LED Lights for Cannabis: What Works and What Doesn't?

Bjorn Dawson November 17, 2020

LED Lights for Cannabis Growth


Whether you’re a new grower or you’re just trying growing cannabis with LED lights for the first time, we bet you’ve got a lot of questions.

If you’re an experienced grower, you’ll remember when HID or CFS lights were the main options for indoor grows - and they set you back a fair amount of money too!

Fortunately, LED lights are a much more affordable option for growing cannabis indoors. We’ve got the complete rundown on different LED lights, how to match them with your growth cycle, and common mistakes to avoid. 

Can You Grow Marijuana With LED Lights?

Short answer, yes. But you need the right type!

In theory, you could use a standard household LED light for marijuana cultivation… but you might not get particularly good results. By standard household, we mean a standard full-spectrum white-colored LED light. These will contain some amount of light from all the color spectrums - but to maximize your yield, you need lights made to emit the right spectrum of colors at the right time to suit your plant’s growth cycle.

For example, in the vegetative cycle, you need more blue light, and in the flowering cycle, you need more red light. This is why it’s always best to use purpose-built LED lighting for your indoor growth.

There are different types of LED lights available to choose from. 

LED Lights for Cannabis

There are three main types of LED lights for growing cannabis indoors - standard LED, COB LED, and spread-style LED. The one you choose will depend on your budget and individual grow space. 

Standard LED

Probably the oldest type of LED light available and still very popular, these are also known as purple lights or purple LEDs. This is due to the purple hue they emit - although they’re actually usually a mix of red and blue LEDs as opposed to any purple!

These lights contain tonnes of small to medium wattage LEDs in a compacted space. Standard LEDs are usually cheap and available to order online worldwide. This is both a pro and a con because the quality can also be compromised due to their price point.
This means they can be unreliable and break easily and give out less light than other types of LEDs. More expensive purple LEDs now often include UV LEDs or COB LEDs to remedy this.


COB is an acronym - it stands for ‘chip on board’. It refers to the fact that a COB LED is made up of hundreds of LED lights on a single chip. Instead, many different colored LEDs spread over the whole light fixture (like with standard LEDs). 

COB LEDs are expensive, but they’re very efficient as they produce a very intense light similar to natural sunlight. This intensity means COB LEDs generally produce good yields, as well as being more energy-efficient than non-LED lighting options. 

Spread-Style LED

Spread-style LED fixtures are made up of a large quantity of tiny LEDs, spread across a large panel or board. Alternatively, they can come in a rack-style or spider-style, though generally, these are used for commercial grows. 

Spread-style LEDs are energy-efficient, so you get the most intense light available for the wattage. Like COD LEDs, they can be far more expensive than standard LEDs. 

Other Types of Cannabis Grow Lights

Aside from LED, or light-emitting diode lights, there are a couple of other options for cannabis grow lights, which we mentioned in the introduction. The most common ones are high-intensity discharge lights (HID) and compact fluorescent lights (CFL). 

HID lights used to be the most popular for indoor grows. They work exceptionally well, but they’re very expensive and use a lot of energy. Prior to LED lights, CFL lights were the more affordable option for those who couldn’t afford HID light fixtures. 

HID lights have been on the decline in popularity since LED lights went mainstream for cultivators. This is because LED lights offer a lot of advantages over more traditional grow light technology. 

Benefits of LED Lights

LED lights have heaps of benefits when it comes to growing marijuana. For starters, they’re generally far more affordable compared to HID fixtures. 

Not only will LED lights cost you less, but they’ll also generally last longer. HID or CFL bulbs will last for up to 20,000 hours, while LED lights can do more than double this for up to 50,000 hours. Of course, this will vary from brand to brand - you get what you pay for!

One of the main advantages of LED lights is how energy efficient they are. HID lights are a great option, but they’ll also up your energy bills by a considerable amount. LED lights emit similar amounts of light without the electricity bill to match. 

Not only are LEDs energy efficient, but they’re also water-efficient comparatively to other types of grow lights. This is because HID lights, in particular, emit a lot of heat, increasing your grow room temperature. Which, in turn, means your plants need more water.

Because LED lights don’t emit these vast amounts of heat, your plants won’t be gasping for water as regularly. This also makes LED lights a great option for summer indoor grows as you’ll have more control over your room temperature - creating less need for cooling systems. 

Tips for Growing with LED Lights

As with all things, there are some pitfalls to using LED lights if you’re inexperienced with them. Avoid common mistakes with these simple tips. 

1. Get the right LED lights

Although most LED lights now are full-spectrum, some are still made only for vegetation. Ensure you’ve got a full spectrum LED light fixture if you’re using the same lights throughout your grow. You’ll also need the right amount of lumens (not wattage!) for your grow space. 

Additionally, don’t cheap out. It can be tempting when you see a full spectrum set for half the price of a well-known brand. But low-quality LEDs can emit too little light, break more easily, and may not have been checked as thoroughly for electrical safety requirements. 

If in doubt, ask on a grow forum about a particular LED fixture for honest, reliable feedback.

2. Set your light at the proper distance

This can be too far away or too close! Your plants will over-stretch, trying to reach the former, or bleach and burn due to the latter. There is no standard perfect distance we can give you, as it will vary depending on the growth cycle and your specific grow light fixture, so read your manual!

If there’s no information there, then a general rule of thumb is to keep your LEDs between 30cm to 45cm away from your canopy during vegetation. You can move this a little closer during flowering, but keep an eye out for any curled, dry, or brown leaves. 

3. Too much water

As we mentioned above, one of the big benefits of LEDs is that your plant will require less water. But if you haven’t taken this into account, you may actually end up overwatering your plant. It’s a common mistake for beginners, so adjust your schedule accordingly.

Marijuana LED Grow Guide

Most LED lights are full spectrum. This means they’ll work for all stages of your plant’s growth cycle - from seed to harvest. But there are some things to keep in mind when using LED lights in different growth stages. 

For Seedlings

Seedlings are really sensitive to intense light, so you need to be careful if you’re using strong LEDs. Dim them if possible, or move them further away from the seedling if this isn’t an option. Though not too far or you’ll end up with a lanky, skinny plant.

If you’re lucky, your LED will have a switch for vegetative and flowering stages. Set this to vegetation as it will emit a cooler blue light more suited to seedlings. This should be on an 18-6 light cycle generally. You can increase light intensity as your seedling establishes itself. 

During Vegetation

You’ll generally have your plant on either an 18-6 light schedule or a 20-24 light cycle. Either way, monitor your plant closely. If it’s looking skinny and tall, your light may be too far away or too dim. 

For Flowering

If your LED has a flowering switch, now’s the time to use it!

If not, you’ll be changing to a 12-12 light schedule for flowering. You’ll also want to crack the dimmer back up if you’ve previously turned it down for vegetation or lower your fixture down. 

Again, monitor your plants closely to ensure they’re getting enough light and making sure they’re not getting too much. Browning, curling, or dryness can all be signs of burning. 

LEDs are Easy with Grobo

Grobo is an automated grow box. That means all you have to do is add your plant, pick your grow recipe from our app, and the system does the rest.

Your Grobo includes a full spectrum 150-watt responsive LED lighting system. You never need to fiddle around with your LED lights for cannabis growing because it's all done for you.

With Grobo you can expect to grow approximately 2 to 3 ounces every 3 or 4 months. We've got plenty more growing tips available on our YouTube channel.

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