7 Best UVB LED Grow Light for Weed in 2026

Updated for 2026 — This article has been reviewed and updated with the latest recommendations.

UVB light has become one of the most talked-about topics in cannabis growing. Research suggests that exposing cannabis plants to controlled UVB radiation during the flowering stage can increase trichome production and THC content. The theory is that the plant produces more resinous trichomes as a natural defense mechanism against UV radiation, similar to how humans produce melanin in response to sun exposure.

Here are the best UVB grow lights for cannabis in 2026.

Best UVB Grow Lights Compared

1.

Solacure Flower Power UVB

The Flower Power is purpose-designed for cannabis and produces the highest UVB output of any fluorescent tube available to home growers. It emits in the 290-310nm range, which is the specific UVB wavelength band most associated with increased trichome production. The tube fits standard T12 or T8 fixtures depending on the model you choose.

Run it for 2-4 hours per day during the last 3-4 weeks of flowering. Starting with shorter exposure and gradually increasing prevents light stress. Position the bulb 12-18 inches above the canopy for best results. At $45-55 for the bulb (fixture sold separately), it is the most cost-effective way to add meaningful UVB to your grow.

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2.

Agromax Pure UV T5 Bulb

Agromax offers a T5 fluorescent UVB bulb that fits standard T5 HO fixtures. The UVB output is moderate compared to the Solacure, which makes it a safer starting point for growers new to UVB supplementation. Less UVB means less risk of burning plants if you get the distance or duration wrong.

The T5 form factor is convenient since many growers already have T5 fixtures for seedlings or supplemental lighting.

Just swap in the Agromax bulb during late flower. At $25-35, it is the cheapest way to experiment with UVB.

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3. California Lightworks UVB Bar

California Lightworks offers a dedicated LED UVB bar that mounts alongside your main grow light. LED-based UVB is more efficient and longer-lasting than fluorescent tubes, and the bar design integrates cleanly into tent and room setups.

The spectrum is tuned specifically for cannabis applications.

The bar includes a built-in timer for scheduling UVB exposure, which is critical since too much UVB can damage plants and reduce quality. At $150-200, it is a significant investment, but the convenience, longevity, and precision make it the best plug-and-play UVB solution.

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4.

Reptisun 10.0 UVB T5 HO

Originally designed for reptile terrariums, the Reptisun 10.0 has been co-opted by cannabis growers for years as a budget UVB source. It produces moderate UVB in a range that overlaps with what cannabis plants respond to. It is widely available at pet stores and online.

The UVB output is lower than dedicated grow-oriented bulbs like the Solacure, so you may need to position it closer to the canopy (8-12 inches) and run it slightly longer. At $20-28 for the bulb, it is the most affordable way to test whether UVB supplementation makes a difference in your garden before committing to a more expensive setup.

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5. Mammoth Lighting UVB Bar

Mammoth's UVB bar is built for commercial operations but works in home gardens too. It uses high-output UV LEDs that deliver consistent UVB intensity across the entire bar length. The aluminum housing dissipates heat effectively, and the bar daisy-chains with other Mammoth fixtures.

At $200-250, it is the most expensive option here. But for growers who want the highest-quality UVB LED bar available, Mammoth delivers commercial-grade construction and performance.

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Safety and Usage Guidelines

UVB radiation is harmful to skin and eyes. Always wear protective eyewear and long sleeves when working under UVB lights. Never look directly at an active UVB bulb. Start with short exposure periods (1-2 hours per day) and increase gradually over 1-2 weeks. Only use UVB during the last 3-4 weeks of flowering when trichome production is at its peak. Position bulbs at the manufacturer's recommended distance and never closer, since UVB intensity increases dramatically as distance decreases.