Are under canopy or inter-canopy grow lights worth it?
There is a big trend in the industry to use intra-canopy grow lighting to increase yields but does it work?
The short answer is yes it does. Adding more lighting under the canopy can increase the yield from the same space. However there is a limit to how much top and intra-canopy lighting you can use. Use too much and yields can flatline and even reduce as the plants can get stressed and even damaged.
Current recommended PAR intensity is too low
Current recommended PAR intensity levels (the measure of light that plants use for photosynthesis) are about 900 µmols/m²/second. With modern LED grow lights this equates to about 350 watts per m² or 35 watts per ft².
Recent studies and current practice in the commercial cannabis industry shows that plants will continue to increase growth until about 1,400 µmols/m²/second. This is an increase in grow light wattage to 500 watts per m² or 50 watts per ft².
This can be achieved by increasing the wattage of the top light or by adding intra-canopy lighting. Adding the additional wattage with lighting underneath means you can keep your existing top light. This makes the upgrade much cheaper than replacing your main top light.
Add intra-canopy lighting to increase yields by 50%
Experiments have shown that growers can potentially increase yield from their current grow spaced by 50% with added intra-canopy lighting. The increase in yields is the same whether you increase top lighting or add intra-canopy lighting.
The graph below shows the results of 4 tests. The total light delivered to the plants was increased with top lighting and intra-canopy lighting combinations. Up to about 1,400 µmols/m²/second it does not matter which you use, the yield will be the same.
Summary of benefits of adding intra-canopy lighting
- 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 intra-canopy grow lights (about 150 watts per m² or 15 watts per ft²)
- 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)
- Size and quality of lower 'popcorn' buds increase
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 effecting 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.
