This guide contains everything you need to know about UV light for plants. The what, why and How, as well as the best UV lights for growing indoor. GroIndoor has got you covered! – Gro Indoor
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UV Light for plants: A short guide

by Kunal Khatri 09 Apr 2023

UV Light for plants: A short guide

UV lights have been a topic of debate in the world of planting for years. Some growers believe they are essential, while others believe that its importance is often exaggerated. However, the fact is that all indoor plants require some light supplement, and UV lights are a good option. In safe doses, these lights can work wonders for your plant potency and resistance. However, before we get into all that, let us understand what they are exactly.

What is UV Light?

The electromagnetic spectrum comprises seven waves: radio waves, microwaves, infrared radiation, visible light, UV light, x rays, and gamma rays. UV light, the third one on the list, makes up around 10% of the light from the sun but can also be produced by artificial sources our topic of discussion today.

The different types of UV Lights

UV light is further broken down into three categories by their wavelengths. These categories are:
1. UVA
2. UVB
3. UVC
Let us look into how these three are different and which one your plants need.


UVA is the category of UV light that falls between the 300-400 nm wavelength range. These UV lights have the longest wavelength when compared to the other categories of UV. UVA, along with some UVB, can penetrate through the ozone layer, making them the rays that we are most in contact with. This type of UV light has no harmful effects on animal or human DNA


UVB has a shorter wavelength than UVA, but it still long enough to allow some of the rays to penetrate through the ozone layer. The wavelength of these waves is somewhere between 280-315 nm. It contains about 0.2% of natural sunlight and can cause damage to human and animal DNA.


The third and shortest wavelength on our list is UVC. This short-length (100-280 nm) category is the most damaging of the three. Luckily, they cannot penetrate through the ozone layer due to their wavelengths unless the layer is depleted. Out of all three rays, the only two we are concerned about regarding growing plants indoor are UVA and UVB. Now that we know what types are necessary for plant growth let us see how UV lights work their magic.

The effect of UV light on your plant depends on the type of light and your plant species. In growing environments where plants do not have access to direct sunlight, UV light can be a great way to boost your plants' growth. UV light does this by:

Increasing Flower Quality, Potency, and Weight

UV light, both UVA and UVB, can increase the production of terpenes and flavonoids in your plant, responsible for enhancing the flower's flavor and potency. A study was conducted on the effect that UV lights have on plants; according to that study, the tomatoes grown without UV grew fine but lacked the taste that separates mediocre tomatoes from great ones. Another study found that plants grown without UV light lack over six key terpenes the compound responsible for your flower's flavor and smell. As a commercial grower, your fruit's aroma and taste make you more successful than the competition. What's more is that these lights also increase root mass and veg branching, allowing a heavier harvest.

Giving you an upper hand in the fight against Pests and Diseases

Various studies worldwide have confirmed the effect of UV light on pathogen suppression. By attacking the photosystem in these pathogens through UV light, their spread can be controlled. UV light does this by disrupting the circadian rhythm of the pathogens. Similarly, UV light has also been shown to encourage plants to produce 15 different proteins known to modify the cuticle's thickness, making plants less susceptible to a fungal attack.

Increase the germination rate of your seeds

These lights can shock the plant to increase the rate at which it takes up water, enabling faster germination when starting seeds. Now that we know how beneficial UV light is for plants, let us discuss how you can take advantage of it.

How Often Should You Give Plants UV Light?

Many inexperienced growers are under the false impression that these lights are useless and a waste of money for your plant. However, the truth can not be further from it. We suggest using UV lights throughout the entire plant cycle to reap the most benefits. Doing this enables your plant to grow healthier, heavier, and more resistant to diseases. To make the most of them, we recommend using UV lights in small doses throughout the plant's life, rather than exposing your plant to heavy doses randomly. Following are a few other frequently asked questions about UV lights and its effect on plants:

How Much UV light does my plant need?

The answer to this question depends on every plant's specific needs; however, keep in mind that generally, all plants require a very low dosage. A 2-3 watt UV light would work well per every square foot of your growing room.

Should I take any precautions while dealing with UV lights?

High exposure to these lights can be harmful to both you and your plant. As UVA and UVB both can penetrate different levels of your skin, we recommend wearing full-sleeved clothes and protective eye goggles while you work with them.

What are the Best UV Lights for Plants?

Now that we have answered a few of the most frequently asked questions let us discuss the best UV lights for plants. Many full-spectrum LEDs emit lights that successfully mimic that from natural sunlight. Some ceramic (CMH) grow lights and double-ended bulbs can also be used as your artificial UV light source. Continue reading for our favorite "UV Spectrum Grow Lights"

1. Black Dog LED Grow Lights

The first light on our list is from the industry-leading company called Black Dog. Known across the country as "the best LED grow lights," these lights boast a well-researched design and produce just the right spectrum for your plant, thanks to Black Dog's use of Phyto-Genesis Spectrum. The high-tech involved in their design makes affording these lights a little difficult for all growers.

2. California Lightworks LED Grow Lights

Another popular company is California Lightworks. They have a great collection that can help you get the results you want. Some of our top recommendations include:

3. Phantom PHENO 440LED Grow Light

Suitable for both flowering and vegetative stages, the Multi Phase (MP) spectrum provides ideal red to blue ratio for vigorous growth and to maximize flower development.

4. Growers Choice Grow Lights

Last but certainly not least, The unique combination of gaseous materials in their lights produces consistency in the spectral output, while still surpassing the competition by leading the industry with the highest levels of PAR output without sacrificing any lamp life expectancy or degradation of the proprietary spectrum.

Choose for all your UV light needs! has a collection of hundreds of products for all your seeding, growing, and harvesting needs. Visit our website today, and get shopping today!

May 6th 2021
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