Optics Mag is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Read more.

Do Plants Need Ultraviolet Light? The Interesting Answer!

Last Updated on

Plants Ultraviolet Light

Contrary to what many believe, plants do not necessarily need ultraviolet light. Instead, they need red and blue light. Blue light stimulates chlorophyll production. Chlorophyll is a pigment necessary for photosynthesis.

However, if given in the correct dose, ultraviolet light can help encourage plant oil production. These oils give the plant a better smell. They also help to protect the plant from pests and diseases.

So, while plants don’t need ultraviolet light, it can be beneficial in small doses. We explain this in more detail below.

magnifying glass 2 divider What Is Ultraviolet Light?

UV light is electromagnetic radiation with a shorter wavelength than visible light. Thus, it is invisible to the human eye.

UV light is divided into three sections and measured in nanometers (nm).

  • UVA: 315–400 nm
  • UVB: 280–315 nm
  • UVC: 100–280 nm

It’s important to note that UVC radiation is the most harmful. However, it is also the shortest wavelength and is mainly filtered out by the Earth’s atmosphere. For this reason, UVC light is not something we need to worry about when it comes to plants.

Plants Ultraviolet Light
Image Credit: Svyatoslav Balan, Shutterstock

How Does Ultraviolet Light Benefit Plants?

Some studies have shown that UV light can help to increase the production of essential oils in plants. It also offers other benefits.

Faster Photosynthesis

Photosynthesis is the process that helps plants to convert light into energy. The energy is used for various functions, including growth and reproduction.

A study showed that UV-A exposure helped increase the rate of photosynthesis by 12%. Another study also found UV-A to help improve the plant’s dry weight, growth potential, and size.

However, there’s no indication of whether other wavelengths would have the same effect.

Protection from Pests

The fungus affects plants by causing them to rot. It thrives in humid conditions and can quickly kill a plant if left untreated.

Fortunately, UV light has been shown to help protect plants from fungus. In addition, studies show that UV-B radiation can help to kill various types of fungi. It does so by changing the genetic makeup of the fungi. As a result, it prevents the fungi from being able to reproduce.

Increase in Resins and Oils

In plants, resins and oils are produced to defend against herbivores and pathogens. These substances can negatively affect the growth, development, and health of animals that consume them. Some of these effects include reduced growth, fertility, and immunity.

In addition, resins and oils can also cause liver and kidney damage.

UV light can help increase the production of resins and oils in plants. In this way, it equips the plant with better defense mechanisms against herbivores and pathogens. UV light can also help improve the quality of these substances.

Plants Ultraviolet Light
Image Credit: Sunny_Smile, Shutterstock

Improves Smell and Taste

In some cases, UV light also improves the smell and taste of plants. It can help break down specific molecules contributing to bad smells and tastes.

In addition, UV light can increase the production of molecules that cause good smells and tastes. Some examples of these molecules include terpenes, responsible for some plants’ unique smell.

Do Your Indoor Plants Need UV Light?

Nowadays, it’s easy to find UV light bulbs that can be used indoors to provide your plants with the UV light they need.

If you have ever wondered if your indoor plants need UV light, the answer is probably yes. While some plants can get by without it, most will do better with at least a little UV light.

It could help them to grow faster, produce more flowers, and stay healthier overall. However, if you are interested in giving your plants UV light, there are a few things you should know.

  • First, not all plants need UV light. If you are growing plants that originate from shady areas, they probably don’t need UV light.
  • UV light can harm humans, so you must take precautions when using it. Make sure the area where you use the UV light is well-ventilated.
  • If you have kids or pets, ensure they can’t get to the UV light bulb.
  • Finally, don’t expect miracles from UV light. While it can help your plants grow better, it’s not a cure-all. It’s just one part of providing good care for your plants.

How Does Overexposure to UV Light Harm Plants?

While there are a few benefits of controlled doses of UV light for plants, too much exposure can have harmful effects. The UV light causes the plant leaves to dry out, which can eventually lead to the death of the plant.

Here are some hazards of excessive UV exposure:

Plants Ultraviolet Light
Image Credit: Sunny_Smile, Shutterstock

Stunted Growth

Too much exposure to UV rays can stunt the growth of a plant. As a result, the plant may produce smaller leaves and stems, and the overall size of the plant may be reduced.


Leaves that are exposed to too much UV light may change color. For example, the leaves may become yellow, brown, or red.


UV light can also cause burns on the leaves of a plant. These burns appear as brown or black patches on the leaves.

DNA Damage

Since they’re sessile (unable to move), plants can’t escape from harmful UV rays. It can damage the plant’s genetic material, leading to death. Likewise, it can affect seed production and germination.

UV-B is especially harmful to plants since it can penetrate the atmosphere and reach the ground. It is a stressor, an agent that causes some sort of stress on the plant. Too much UV-B exposure can cause a plant to produce fewer leaves, flowers, and fruits.

Plants Ultraviolet Light
Image Credit: nieriss, Shutterstock

How to Use UV Light Sources in a Grow Room?

You may want to consider using UV light sources if you have a plant grow room. However, here are a few factors to consider beforehand.

Light Needs

Not all plants need UV light, but some benefit from it. For example, plants grown for their flowers or fruits may produce more vibrant blooms or fruits when exposed to UV light.

If unsure whether your plants would benefit from UV light, consult a professional or do some research online.

Height Limitations

Do not put the UV light source too close to your plants, as it can bleach the leaves. Bleaching is a process where the green chlorophyll in the leaves is broken down, causing the leaves to turn white.

If you want to use a UV light source, place it at least 2–3 feet above the tallest plant in the room. Plus, make sure UV bulbs are spaced at least 12 inches apart to prevent leaves from being burned.

Plants Ultraviolet Light
Image Credit: nieriss, Shutterstock

Duration of Exposure

The time your plants are exposed to UV light will also affect them. For example, if you have a 12-hour light cycle for your plants, only expose them to UV light for 6 hours.

You can start with shorter periods of exposure and increase the time as needed. Just pay attention to how your plants react to the light.

Types of UV Light Sources for Grow Rooms

If you grow plants in natural sunlight, they will get their share of UV light from the sun. But what if you want to grow indoors, or your outdoor plants need extra help? In these cases, you may need to supplement your plants’ exposure to UV light using an artificial light source.

There are a few types of UV light sources you can use.

MH (HID) and HPS Grow Lights

An MH (metal halide) or HPS (high-pressure sodium) grow light can be a great source of UV light for your plants. These lights are typically used as the primary light source for indoor plants, emitting a lot of UV light.

LED Grow Lights

LED grow lights are popular among horticulture enthusiasts. They are energy-efficient, long-lasting, and emit very little heat.

Some LED grow lights also emit UV light. You can find LED grow lights with UV diodes to emit UV-B wavelengths.

Plants Ultraviolet Light
Image Credit: kukurund, Shutterstock

T5 Grow Lights

A T5 grow light is a type of fluorescent light. These lights are commonly used to supplement the primary light source in a grow room.

You can also search for T5 bulbs that allow you to set the wavelengths emissions needed for the flavor enhancement of every yield. Again, these may be costly but will save you time and money in the long run.

magnifying glass 2 divider Final Thoughts

To conclude, UV light benefits plants by producing better resin, faster photosynthesis, and flavor enhancement. However, excessive UV exposure can bleach leaves and stunt plant growth.

Therefore, you must find the right balance when using UV light on plants. If you want to use UV light in a grow room, do thorough research beforehand.

Featured Image Credit: Helga_777, Shutterstock

About the Author Jeff Weishaupt

Jeff is a tech professional by day, writer, and amateur photographer by night. He's had the privilege of leading software teams for startups to the Fortune 100 over the past two decades. He currently works in the data privacy space. Jeff's amateur photography interests started in 2008 when he got his first DSLR camera, the Canon Rebel. Since then, he's taken tens of thousands of photos. His favorite handheld camera these days is his Google Pixel 6 XL. He loves taking photos of nature and his kids. In 2016, he bought his first drone, the Mavic Pro. Taking photos from the air is an amazing perspective, and he loves to take his drone while traveling.