Does Intra Canopy Grow Lighting Work?

This is a guest article written by Shane from the MIGRO grow lighting channel. View more grow lighting articles from Shane in his blog posts here.

Does Intra Canopy Grow Lighting Work? 

Traditionally, indoor growers hang their grow light above the plants. However, the top layer of leaves in the canopy absorb over 90% of the light from above. This means the lower leaves are not receiving much light or being fully utilized. It is now possible to get more productivity from this lower growth with intra canopy grow lights.

Modern LEDs do not emit much heat and can be formed into long LED bars. This allows growers to position LED grow lights within the canopy to deliver light to the lower leaves.

For many years, commercial greenhouse growers of cucumbers and tomatoes have supplemented sunlight with intra canopy LED grow lighting. They use it in winter when the sun is weak to extend the growing season. In summer they also use intra canopy grow lighting to increase the yield from their existing grow space. It is proven in the commercial greenhouse world but how does it translate to the indoor cannabis growing situation?

Studies have shown that adding intra canopy lighting will deliver the same yield per watt of lighting as top lighting and for some strains intra canopy lighting will produce a better yield per watt than top lighting. The quality of the harvest also improves. Intra canopy lighting improves bud size and density. Smaller buds from the lower parts of the canopy are increased in size and mass.

When To Use Intra Canopy Grow Lighting

Cannabis plants are able to absorb and use very high light intensity of about 1,400 µmols/m²/second of PAR (Photosynthetically Active Radiation, the part of the light spectrum used by plants to grow). Exceeding that level and the additional electrical energy used does not yield enough growth to make it worthwhile.

However, if your top light is not achieving an average PAR intensity of 1,400 µmols/m²/second then you can add intra canopy lighting to increase the yield from your space. To achieve 1,400 µmols/m²/second your total grow lighting power must be at least 50 watts per square foot or 550 watts per square meter.

We recommend splitting your top lighting to intra canopy wattage about 60:40. We recommend the following approximate power split between top and intra canopy lighting for the most popular grow sizes.

The Best Light Spectrum To Use For Intra Canopy Lighting

Most LED grow lights are now ‘full spectrum’ with a mix of white and red LEDs. The spectrum output of the intra canopy light should be full-spectrum and similar to the top light.

Summary Of Benefits Of Adding Intra Canopy Lighting

• You can Increase the yield from your grow space by 50% with added intra canopy lighting
• Keep your existing top light and add 50% more wattage with about 150 watts per m² or 15 watts per ft² of intra canopy grow lighting
• Reduce stress on the top flowers by adding light underneath instead of a bigger top light (plants can re-veg and foxtail with very high PAR intensity)
• Increases the size and quality of lower 'popcorn' buds

Tips For Adding Intra Canopy Or Under Canopy Grow Lights

• Make sure the grow light is rated for a damp environment, minimum of IP56 rated. Condensation will drip onto the light fixtures from the plants.
• The LEDs should be covered and sealed. If dirt or moisture sits directly on the LEDS it will damage them and possibly cause a fire.
• It is better if the LED driver in not in the light fixture but located remotely. The LED driver outputs a lot of heat which will increase the temperature in your canopy affecting the final quality of your harvest.
• You can add the intra canopy lighting underneath facing up or at the side facing inwards. Just keep buds and leaves a minimum of 3" or 7.5cm away from the light as the light stress will damage them.