The Top Five Under Canopy Lighting Mistakes

Under canopy lighting (UCL) is a powerful tool for increasing yield, quality, and consistency. However, simply plugging in the lights doesn't guarantee success. Many growers leave significant yield on the table by making a few common errors. Below, we explore the five most common mistakes and how you can avoid them to maximize your ROI.

Mistake #1: Excessive Under-Clearing

Traditionally, cultivators have been taught to "lollipop" or heavily under-clear their plants to prioritize the top canopy. While this makes sense for top-down lighting, it defeats the purpose of Under Canopy Lighting. This is one of the most common mistakes we see, because it flies in the face of conventional cultivation practices. It feels weird to us, too. 

The benefit of UCL is the ability to holistically light the plant, allowing you to harvest high-quality yields from top to bottom. If you clear out all the lower growth, you're removing the very sites the lights are designed to boost. You're basically trimming profits, which is almost never a good idea.

The Solution: Strategic De-leafing

• LIMIT EARLY CLEARING: Reduce under-clearing during the vegetative stage and early flower.
• TIMING: Perform a strategic de-leafing after stretching has stopped, typically around Day 20 to 25 or after the plants have stopped stretching.
• THE GOAL: Open up the plant to create a mix of top and bottom light in the center, allowing for uniform light.
• TARGET CANOPY DEPTH: At Faven, we aim for a canopy depth of 4 to 4.5 feet. This height maximizes the ability for top and bottom lights to light the plant.

Mistake #2: Not Adjusting to the Increased Demands

Adding lights to the bottom of the plant increases its metabolic rate. This is often the biggest learning curve for growers transitioning to UCL. Your plants will be hungrier and thirstier than before. It's a little bit like sending your plants to the gym or on a long run.

We typically see water demand increase by 10% to 20%, depending on the genetics. If you don't adjust your irrigation, you risk stressing the plants and limiting their potential.

Managing Irrigation

Monitor your P1 and P2 watering schedules closely. Ensure your volume increases to match the plant's accelerated growth. Watch for dry-backs and adjust accordingly to maintain a healthy root environment.

Manage EC Input

While increasing irrigation volume is a constant in all under-canopy applications, the need to increase fertilizer input is not. If a nutrient deficiency is documented, simply increasing EC input by approximately 10% is typically sufficient to correct it.

Mistake #3: Poor Lighting Timing and Intensity

Timing is everything. This is true in dating, investing, and cultivation. I have only figured out the timing of one of those things. The other two are still a complete mystery.

 A frequent mistake is starting the under-canopy lights too late in the flower cycle. This can lead to a disparity in maturity between the top and bottom of the plant. It’s sort of like waiting too long to text someone after a first date or selling a stock just before a company releases a kick ass product. 

I have made all three of the above mistakes, but I finally figured out the ideal timing when it comes to under canopy lighting.

The Ramping Strategy

Start your under-canopy lights early—ideally around Day 5-10. This helps the bottom buds mature at the same rate as the tops, ensuring a uniform final product. Start low and increase intensity slowly to avoid any adverse effects or light stress. We aim to be at 100% intensity by the end of the plant's stretching phase.

Mistake #4: Improper Use of Trellis Support

When you use UCL, your lower branches will pack on weight that they wouldn't have in a traditional setup. If these branches aren't supported, they will flop onto your rolling tables or even the lights themselves. This can dirty the lenses and block the upward path of the light itself. 

The 3-Inch Rule

We recommend setting your first trellis layer as low as possible—about 3 to 4 inches above the lens of the light. This allows the trellis to catch and support those lower branches as they gain weight, ensuring the plant's energy is used for bud production rather than structural support.

Mistake #5: Excessive Planting Density

Stuffing too many plants into a given space can negate the benefits of UCL. If plants are too crowded, the stalks and stems will block the upward movement of light, preventing it from reaching the middle of the canopy.

In the current market, this is an easy mistake to make. Narrow margins are squeezing almost all of us, but it’s important to ensure you get the most out of your under canopy light investment. You need a high yield, and UCL companies need happy customers.

Density Recommendations

Density Recommendations rule of thumb: the larger the plant, the lower the density should be. Give your plants room to breathe and absorb the light holistically.

Final Thoughts

Under canopy lighting is a significant adjustment and added expense for modern cultivators. It requires a shift in traditional techniques. By avoiding these five mistakes, you can ensure your facility sees the best possible return on investment. If you have more questions or want to see more educational content, subscribe to the Faven Lighting YouTube channel, DM us on Instagram or reach out to us directly!

Let us know if you have discovered any under canopy light mistakes we have missed in the comments below.