The 3 Best UV Grow Lights: Increasing Growth And Yield For Indoor Plants

UV light close-up

For some growers, it may seem counterintuitive that harmful radiation, such as UV light, can have a positive effect on plants.

But nature works in weird ways.

UV light can actually help you increase the yield and quality of your growth. So, adding a UV lamp to your lighting system can be very useful.

In this article, we’ll show you the best three UV grow lights for indoor plants.

Plants and UV light

Before we show you our list of the best UV grow lights, there are few things you should know about UV light and plants.

You can skip this section and scroll down to view our UV grow lights recommendations.

Why Is UV Light Useful for Your Plants?

Plants enjoying the sunrise

UV light is highly energetic, so it can cause damage to living tissues.

Around 3% of sunlight is UV light, so most plants are exposed to UV radiation in their natural habitats.

To shield themselves from the harmful effects of UV lights, plants will activate specific processes and produce certain molecules that have protective functions, such as repairing damage or absorbing UV light.

For indoor plant growers, these processes and molecules are useful in improving the quality and yield of plants.

UV light is a range of wavelengths stretching between 100 to 400 nm. This range is divided into smaller wavelength ranges (UVA, UVB, and UVC). In indoor gardening, UVA (315-400 nm) and UVB (280-315 nm) are mainly used.

There’s a lot of debate going on about whether UVA or UVB is better for plants.


With a shorter wavelength, UVB light holds more energy than UVA light and some growers believe it’s more beneficial. 

The effect of UVB light on plants has been well demonstrated in studies.

One study done on cannabis showed that treating the plant with UVB light resulted in around 30% increase in THC content.

Another study revealed that UVB can make plants more resistant to pests and diseases.

Above all, in some species and in small quantities, UVB light can boost photosynthetic activity.

That said, other studies show that UVA light has similar effects on plants.

For example, UVA light can boost the levels of nutrients and volatiles in different plant species.

The famous grow light brand, Black Dog, did some experiments to show that UVA light can also increase THC in plants.

Same as UVB light, UVA light can also boost photosynthesis and increase yield.

So, since UVA and UVB have similar benefits, why choose one instead of the other?

While UVB light can be slightly more beneficial, it can also have detrimental effects on plants and people.

That’s why today many UV-emitting grow lights put out UVA light instead of UVB light.

Mistakes done while using UVA light can be less dangerous than ones done using UVB. So, UVA light can be handled better by growers, especially starters, than UVB light.

It’s up to you to decide whether you want to use UVA or UVB light for your plants, but in all cases, you should know how to properly use the light.

Important Guidelines to Follow When Using UV Grow Lights

  1. UV light is harmful to humans. It can cause skin damage and cancers. You should use UV lights in an enclosed growing space and wear protective material while working around or under them.
  2. Exposing your plants to UV light for long periods can harm them. For this reason, you need to keep it on for few hours a day only. Stick to the manufacturer’s recommendations to know how long you should keep the light on each day.
  3. Keep enough distance between your plants and the light to avoid damaging them.
  4. Don’t use any UV light for your plants. Some UV lights can be very intense, and they can destroy your growth.

Best UV Grow Lights for Plants 

Here are three superior UV grow lights that will improve your growth:

1. HLG 30 UVA Supplement

HLG 30 UVA Grow Light

HLG is a famous brand of grow lights that manufactures first-class products.

Their HLG 30 UVA supplement is one of the best UV grow lights on the market.

The light is basically a 24-inch-long LED bar that contains 365nm and 385nm diodes (in the range of UVA light).

HLG 30 UVA supplement can cover a 4’ x 4’ (1.2m x 1.2m) to 5’ x 5’ (1.5m x 1.5m).

The device draws around 30 watts of power only, so it won’t cost you a lot of energy.

It’s also waterproof, so it’s great for humid growing environments.

The grow light is very affordable taking into account that UV lights are usually expensive.

Although this is UVA light, take the necessary precautions and follow the manufacturer’s guidelines while using HLG 30 UVA supplement in your growing environment.  

2. California Lightworks SolarSystem UVB

California Lightworks SolarSystem UVB Grow Light

California Lightworks is the only manufacturer that has integrated UVB light in its full spectrum grow lights.

And the brand’s SolarSystem UVB is without a doubt the best UVB light on the market.

California Lightworks SolarSystem UVB is a T5 fluorescent lamp and not an LED grow light.

The light draws around 24 watts and has a power output of around 320 μW/cm² at 24 inches. For reference, UVB light measures around 200 to 280 μW/cm² on a sunny day.

California Lightworks SolarSystem UVB can cover a 4’ x 4’ (1.2m x 1.2m) growing area.

The light has a special design that allows you to control up to 10 units using a single switch or timer.

The recommended distance between the plants and this light is 24 to 36 inches.

This light is also relatively affordable.

Caution: Don’t work around this light without wearing protective equipment and don’t look directly into the light.

3. TotalGrow UVA Bar

TotalGrow UVA Bar Grow Light

TotalGrow UVA bar is another great UVA light for plants.

The UVA grow light is monochromatic with a spectrum of 385 nm (high UVA).

TotalGrow UVA bar has a UVA output of around 40 µmol/s, and it can cover a 2’ x 4’ (0.6m x 1.2m) growing space.

It draws around 30 watts, so it has an efficiency rate of around 1.3 μmol/J.

The minimum recommended hanging height for this light is 24 inches.

TotalGrow UVA is waterproof and has a daisy chain feature that allows you to connect up to 24 to 48 units together (depending on the voltage).

The light has a 30,000 lifespan and comes with a 3 years warranty.

The price of this light is comparable to that of 1 HLG 30 UVA Supplement.

Final Words

UV lights can help you improve your growth and yield.

However, you need to know how to use them properly, or else you could damage your plants.

Always follow the recommendations by the manufacturer and do your own research before using UV grow lights.

You can also test your UV lights with different plants before using them with your main crop.

And finally, we cannot overemphasize the importance of taking the necessary precautions while working around these lights.

Happy growing. Please share your thoughts in the comments below and don’t hesitate to contact us if you need more help!

Blogger, Gardener | + posts

I'm Jad, a biologist, blogger, and experienced indoor gardener. I am knowledgeable in plant biology, particularly in plant cultivation and propagation. I founded in 2019 to share my knowledge in indoor gardening with passionate home growers.