The Best Way to Add UV Light to Your Grow in 2025
As growers continue to refine their setups, UV grow lights are becoming an essential tool for maximising yield, potency, and plant health. The right amount of UV-A and UVB light, especially the benefits from a full spectrum of light including UV rays, can increase essential oil production, boost terpene profiles, improve photosynthesis, and even protect plants against pests and diseases.
In this guide, we’ll cover everything you need to know about UV light in indoor growing, including:
- Why plants need UV light
- The best types of UV light for grow lights for 2025
- How long to run UV light for optimal results
- Common mistakes when using UV supplementation
Whether you’re a home grower or a large-scale cultivator, understanding UV light can help you grow stronger, healthier, and more potent plants.
What is UV Light & Why Do Plants Need It?
UV (ultraviolet) light is part of the electromagnetic spectrum, sitting just beyond visible light. It’s divided into three types:
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UV-A (315-400nm) – Promotes photosynthesis efficiency, enhances terpene production, and stimulates natural plant defences.
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UV-B (280-315nm) – Increases resin and flavonoid production, which improves flavour, aroma, and overall plant quality when combined with red wavelengths in the wavelength range that includes UV-B.
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UV-C (100-280nm) – Used for sterilisation, but can be damaging to plants and is not commonly used in grow lights (you can find this on air sanitisers such as the AirTitan).
In nature, plants are exposed to UV from the sun, but in indoor growing, standard LED grow lights often lack UV wavelengths. This means adding UV supplementation can replicate natural sunlight and unlock a range of benefits.
The Benefits of Adding UV to Your Grow
1. Increased Terpenes & Essential Oils
UV exposure stimulates secondary metabolite production, leading to:
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Stronger aromas and flavours in herbs, fruits, and flowers.
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Increased levels in resin-producing plants.
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Greater overall potency in medicinal and culinary crops.
UV triggers natural plant defences, helping protect against:
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Mould & mildew – UV-B exposure thickens leaf cuticles, making it harder for fungal spores to take hold.
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Pests – UV can disrupt pest life cycles, reducing infestations without chemical sprays.
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UV light reduces inter-nodal stretching, leading to denser, bushier plants.
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Strengthens stem and root development.
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Ideal for high-intensity growing environments.
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UV-A light enhances photosynthesis by stimulating chlorophyll production.
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UV helps plants absorb and use nutrients more efficiently.
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Leads to higher yields with greater biomass production.
Best UV Grow Lights in 2025
Using dedicated UV grow lights ensures plants receive the correct spectrum without the risk of overexposure. If you want to increase resin production, enhance terpene profiles, and improve plant resilience, these are the best UV grow lights available in 2025.
1. Lumatek 30W UV Supplemental LED Bar
The Lumatek 30W UV Supplemental LED Bar is one of the most efficient and reliable options for growers looking to introduce UV-A and UV-B wavelengths into their grow room. Designed to work seamlessly alongside Lumatek Zeus LED fixtures, this high-performance supplemental light ensures balanced UV exposure without overwhelming plants.
Key Features & Benefits:
- 30W of targeted UV-A & UV-B output – Enhances terpene and resin production for higher-quality yields.
- UV-A (365nm) and UV-B (315nm) wavelengths – Mimics natural sunlight exposure to stimulate secondary metabolite production.
- IP65-rated for durability – Built for humid environments, ensuring longevity and reliable performance.
- Lightweight & easy to install – Can be daisy-chained with multiple units for larger coverage.
- Perfect for flowering – Encourages higher potency and essential oil production in late-stage growth.
Shop the Lumatek 30W UV Supplemental LED Bar
2. Maxibright Daylight 60W UV-A & UV-B LED Bar
For growers looking for a more powerful UV solution, the Maxibright Daylight 60W UV-A & UV-B LED Bar offers double the wattage, making it ideal for larger setups and high-intensity environments. It’s specifically designed to pair with Maxibright LED systems but can be used in any grow space for enhanced UV exposure.
Key Features & Benefits:
- 60W UV output – Provides higher intensity for improved terpene and flavonoid development.
- UV-A & UV-B spectrum – Targets essential oil and resin production, boosting overall plant quality.
- Passive cooling system – Ensures silent operation and maximum efficiency.
- Flexible installation – Works with Maxibright LED fixtures or as a standalone unit in any grow room.
- Optimised for flowering – Encourages thicker resin production and higher cannabinoid content.
Shop the Maxibright Daylight 60W UV-A & UV-B LED Bar
Which UV Grow Light Should You Choose?
Both Lumatek and Maxibright offer high-quality UV supplementation, but the best choice depends on your grow room size and intensity needs:
- For precision UV control with a compact and durable design, go for the Lumatek 30W UV Bar.
- For a more intense UV boost with higher wattage output, the Maxibright 60W UV Bar is a powerful alternative.
No matter which option you choose, UV supplementation is the key to improving potency, enhancing terpene profiles, and maximising plant resilience.
How to Use UV Light in Your Grow Room
To get the most out of UV supplementation, follow these best practices:
1. How Long Should You Run UV Light?
Using too much UV can damage plants, so timing is key.
|
Stage |
UV Duration Per Day |
Benefits |
|---|---|---|
|
Vegetative |
1-2 hours max |
Helps with pest resistance & compact growth |
|
Early Flower |
2-4 hours |
Enhances resin production & terpene expression |
|
Late Flower |
4-6 hours |
Maximises potency & aroma |
Pro Tip: Start with low exposure times and gradually increase to avoid plant stress.
2. Where Should You Position UV Lights?
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Place UV bars at canopy height for even distribution.
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Keep them separate from main LEDs to control exposure independently.
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Use reflective materials in your grow tent to prevent hotspots.
3. When Should You Start Using UV?
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Seedlings & Early Veg – Avoid excessive UV to prevent stress.
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Mid to Late Flowering – The best time for UV exposure to boost terpene and resin production.
Common Mistakes When Using UV Grow Lights
- Using UV for too long – Overexposure can cause leaf burn and stress.
- Placing UV too close to plants – Can result in hotspots and uneven growth.
- Not adjusting intensity – UV should be gradually introduced to prevent shock.
- Using low-quality UV bulbs – Inferior lights don’t provide the right spectrum.
Advanced UV Growing Strategies for Maximum Yield and Potency
As more growers recognise the benefits of UV lighting, the demand for precise supplementation strategies is increasing. While many guides cover the basics, optimising UV for different plant species, grow spaces, and stages of growth can take results to the next level.
In this expanded section, we’ll dive deeper into advanced techniques, covering:
- The science behind UV stress and plant responses
- Customising UV exposure for different crops
- How UV interacts with other grow light spectrums
- Integrating UV into hydroponic, soil, and aeroponic systems
The Science Behind UV Light Stress & Plant Adaptation
Plants evolved under natural sunlight, which includes UV radiation and varying light conditions. However, excessive UV exposure can cause stress, leading to changes in growth patterns, metabolic activity, and gene expression.
When plants detect UV light, they:
- Increase production of secondary metabolites – UV stress triggers higher levels of flavonoids and terpenes which protect plant tissues from damage. Recent studies indicate that these compounds play a crucial role in plant defence systems.
- Develop thicker cuticles and cell walls – This makes plants more resilient to pests, environmental stress, and physical damage, playing an important role in their survival.
- Adjust leaf morphology – Plants may produce smaller, thicker leaves to reduce UV penetration.
Understanding these responses allows growers to strategically use UV to enhance yield and plant defences without causing harm.
How Much UV Stress is Beneficial?
The key is controlled exposure. While too much UV can stunt growth and cause bleaching, the right amount enhances quality and resilience by preventing damage from reactive oxygen species.
Ideal UV exposure levels depend on:
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Plant species – Some higher plants thrive with higher UV-B, while others need only small amounts.
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Growth stage – Young plants are more sensitive to UV than mature ones.
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Grow room environment – Temperature, humidity, and CO₂ levels impact how plants respond to UV.
Tip: If plants start yellowing or curling under UV light, reduce exposure and slowly reintroduce it over time.
Customising UV Exposure for Different Crops
Different plants react to UV supplementation in unique ways. Here’s how to optimise UV light use based on what you're growing:
1. Fruiting & Flowering Plants (Herbs, Tomatoes etc...)
UV-B (280-315nm) is the most beneficial for increasing essential oil production and flavour intensity.
Best used during late veg and flowering for higher potency and terpene concentration.
Recommended UV Exposure: 2-6 hours per day in the flowering stage.
2. Leafy Greens & Microgreens (Lettuce, Spinach, Kale, Basil)
Respond best to low levels of UV-A (315-400nm) to boost chlorophyll production, resilience, and leaf size.
Too much UV can cause leaf tip burn, so limit exposure.
Recommended UV Exposure: 1-3 hours per day.
3. Root Vegetables (Carrots, Radishes, Beets, Ginger)
UV exposure improves root size and sugar content.
Moderate UV-A exposure strengthens cell walls and prevents fungal diseases in soil.
Recommended UV Exposure: 2-4 hours per day.
Pro Tip: If you're growing a mix of crops, position UV lights to target flowering plants more intensely while giving leafy greens less exposure.
Grow Light Spectrum & Its Effect When Combined with UV
| Grow Light Spectrum | Effect When Combined with UV |
|---|---|
| Full-Spectrum White LED | Works best with UV, as it replicates natural sunlight. Ideal for terpene and flavonoid enhancement. |
| HPS (High-Pressure Sodium) | HPS lacks UV, so adding supplemental UV-B fluorescent lights boosts resin and oil production. |
| CMH (Ceramic Metal Halide) | CMH bulbs emit some UV, so additional UV should be used sparingly. |
| Blurple LED (Red/Blue Spectrum) | Lacks UV wavelengths, so UV supplementation is essential for quality improvement. |
Tip: For the best results, pair UV supplementation with high-quality LED grow lights to mimic full-spectrum sunlight as closely as possible.
Integrating UV into Hydroponic, Soil & Aeroponic Systems
Hydroponic Setups
Hydroponic growers often overlook UV supplementation, but adding UV improves nutrient uptake efficiency.
- Enhances calcium and magnesium absorption, preventing deficiencies.
- Reduces algae growth in reservoirs by inhibiting microbial overgrowth.
- Recommended UV Exposure: 2-5 hours per day in the flowering stage, depending on plant species.
Soil Growing
- UV improves microbial activity, enhancing organic nutrient breakdown.
- Thicker cell walls make soil-grown plants more resistant to environmental stress.
- Recommended UV Exposure: 3-6 hours per day, depending on plant maturity.
Aeroponic Systems
- UV reduces the risk of pathogen spread in misting environments.
- Helps plants develop stronger roots for better nutrient uptake.
- Recommended UV Exposure: 2-4 hours per day.
Pro Tip: If using UV in aeroponics or hydroponics, monitor plant responses closely, as they may absorb UV more intensely than soil-grown plants.
Best Practices for Safe UV Use in Grow Rooms
- Wear protective eyewear when working under UV light – UV can damage human eyesight.
- Position UV bars strategically – Keep them above canopy level to distribute light evenly.
- Use timers to avoid overexposure – Too much UV can cause leaf damage and nutrient lockout.
- Start with shorter exposure times – Increase gradually as plants adapt.
- Monitor plant response – If leaves curl, bleach, or show stress, reduce UV intensity.
Frequently Asked Questions (FAQs) About UV Grow Lights
1. Is UV Light Essential for All Grow Rooms?
While not essential, UV supplementation greatly improves plant quality, potency, and resilience.
2. How Much UV Is Too Much?
Overexposure can cause:
- Bleached leaves
- Reduced chlorophyll production
- Stunted growth
The key is gradual introduction and monitoring plant response.
3. What’s the Difference Between UV-A and UV-B?
- UV-A (315-400nm) → Enhances photosynthesis and flavonoid production.
- UV-B (280-315nm) → Boosts terpenes, resin, and essential oil production.
4. Should UV Be Used in Vegetative or Flowering Stages?
- Best for flowering – Increases terpenes and potency.
- Use sparingly in veg – To prevent over-stressing young plants.
Want even bigger yields? Pairing UV alongside Under Canopy Lightning
For maximum growth, yield, and potency, pair your main grow light with under-canopy LED lighting to ensure even light distribution across the entire plant. The Omega 120W Under Canopy LED is designed to penetrate lower foliage, reducing shading and increasing photosynthesis where top lighting alone can't reach.
When combined with UV supplemental lighting, this setup delivers even greater benefits. UV light enhances essential oil and resin production, leading to higher potency and improved flavour profiles, while under-canopy lighting ensures that lower bud sites receive the energy they need to develop dense, high-quality flowers. This dual-spectrum approach creates a more even canopy, reduces the risk of popcorn buds, and maximises overall plant performance.
Final Thoughts: Why Every Grower Should Use UV in 2025
UV light was once overlooked, but in 2025, it’s now recognised as a game-changer for indoor growing. Whether you're cultivating medicinal plants, fruiting crops, or leafy greens, UV supplementation can significantly enhance resin production, terpene intensity, and plant health.
If you’re looking to maximise yield and quality, UV lighting is an essential addition to your grow setup.
