How to Increase Trichome Production with LEC Grow Lights

Published May 27, 2021

by Nebula Haze

What is a CMH grow light? (also known as a LEC grow lights)

CMH grow lights (also known as LECs) are great grow lights for cannabis, but they really “shine” (sorry I know) when it comes to producing an excessive amount of trichomes and increasing terpene production.

CMH/LEC grow lights typically produce more trichomes than other grow lights including LEDs… if you use the right bulb

Using LEC/CMH bulbs in the 4100k or 4200k spectrum will dramatically increase the number of trichomes produced in the flowering stage compared to other types of grow lights including LEDs. These bulbs work with any 315 CMH or LEC grow light ballast. Kick it up one more notch by using a 10,000k bulb for the last 1-2 weeks.

Day 30 (week 4) flowering stage - Mandarin Cookies bud

If you’re looking for the best cannabis yields or potency, I recommend going with an LED grow light. But if you’re most concerned with increasing trichome production and smells (and have a relatively cool place to grow; LECs get hot!), LECs may be the best grow light for you.

Sparkle city on this LEC-grown bud

Which LEC/CMH Grow Light Should You Get?

Here are examples of some of the most common and popular LEC/CMH grow lights by different manufacturers. I personally recommend the version by Sun System as it’s produced amazing results with the Philips bulb. In a side-by-side grow journal with an HLG Quantum Board LED, the Sun System LEC produced more trichomes and higher terpene levels even though the clones were otherwise grown in identical conditions (same nutrients, grow space, grow medium, etc.).

The UV rays from LECs cause the plant to produce more trichomes and terpenes as a stress response

  • Sun System 315 LEC <– Recommended
    • Optimal distance from plants: 18-24 inches (45-60cm)
    • Comes with Philips 4200k bulb: excellent in the vegetative stage, and one of the best bulbs for cannabis trichome production
    • Use a 10,000k bulb for the last 1-2 weeks to increase trichome production*
  • Grower’s Choice 315W CMH
    • Optimal distance from plants: 2.5-3 feet (76-91 cm)
    • Comes with an unspecified 3KR Red Enhanced bulb – good for yields but not the best for trichomes
    • Use a 10,000k bulb for the last 1-2 weeks to increase trichome production*
  • Eye Hortilux 315W CMH
  • Vivosun 315 CMH
    • Optimal distance from plants: 24 inches (60 cm)
    • Comes with an unspecified 3100k bulb – good for yields but not the best for trichomes
    • Use a 10,000k bulb for the last 1-2 weeks to increase trichome production*

*a 10,000k bulb will reduce yields if used throughout the flowering stage and should only be used for the last 1-2 weeks before harvest. However, these powerful bulbs have the ability to really crank up the trichomes when used correctly!

Soon you’ll be harvesting buds like this Pacific Punch grown under a Sun System 315 LEC

Can an LEC/CMH grow light be used from seed to harvest?

Yes! Cannabis plants thrive under LECs in both the vegetative and flowering stage all the way to harvest. Here’s a guide with information on how to get set up and use an LEC grow light.

These plants were grown from seed to weed under the Sun System 315 LEC grow light

Young vegetative cannabis plants growing under a 315 LEC grow light

Cannabis plants in the vegetative stage - grown under a 315 LEC grow light

Example of flowering cannabis plants that were grown under a 315 LEC grow lightCloseup of some of those buds

Cannabis cola grown from seed to harvest under a 315 LEC grow light

An auto-flowering cannabis cola (grown under a 315 LEC grow light)

Bonus: Pictures of plants grown under LECs that were submitted by our readers

LEC grown cannabis bud pic by the talented grower Jamie Arellano

Example of a marijuana bud grown under an LEC grow light (Light Emitting Ceramic)Cannabis buds grown with LEC (CMH) grow lights - sparkly and covered in trichomes!

Anonymous submissions

Happy plant under LECs

Submit your LEC or CMH grow light pictures for a chance to be featured here!

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