Why Under

Photo: JumpLights

If you are thinking about under-canopy lighting in your greenhouse, you are not alone. Recently, growers have shown much interest in providing lighting from many different locations with respect to their plants’ needs, including overhead top lighting, in-between intra-canopy lighting, and underneath under-canopy lighting.

Stemming from the desire to continually seek an increase in productivity, intra-canopy and under-canopy arrangements fight against self-shading. The reason we have controlled environments is to beat the productivity we would otherwise get from open fields, right?

At JumpLights, we’ve been building under-canopy lights for the past few years, but the concept was initially challenging for us to grasp because of the uncertainty around how plants would react to light shining upward from under the leaves. Leaves have spent the past 500 million years adapting to sunlight shining down on them from the skies.

But then it started to make sense. We know that reflective plastic mulch increases yields by bouncing light upwards into plant canopies, and we know leaves are semi-transparent. We understand how photons can go through plant tissue to drive photosynthesis, and we have seen how scattered diffused light improves yields without an increase in light intensity. These were the clues telling us the dark sub-canopy of controlled environment agriculture can be lit for huge gains. So, where there is darkness, let the light shine.

Cannabis is a crop with a uniquely dark sub-canopy and tight crop spacing that presents the perfect conditions for using efficient LEDs in a narrow body with an upward-facing form factor.

That’s why it’s important to select a light with a good environmental rating such as UL wet location, a rugged light with protected electrical connections, and a light that can regulate its own heat while also shining brightly along the widest angle possible.

After selecting a rugged bright light for your under-canopy workhorse, successfully implementing it can also be a balancing act. Warehouse-type growing environments may have HVAC or power constraints, but those hurdles can be overcome by replacing top lighting with more efficient LEDs. Choosing how much light to put on top of the canopy vs underneath can be a balancing act as well.

Previously, cannabis growers had been putting 300 to 600 µmol∙m-2∙s-1 whereas now, they are seeing increased yields with values around 700-1,000 µmol∙m-2∙s-1. In publications and in practice, we have seen increasing yields up to 1,500 µmol∙m-2∙s-1 from top-canopy lighting. However, this begs the question, “how much light should be put on top of the canopy vs how much underneath?”

We find that under-canopy lighting is a huge value driver for cannabis operations.

It will be interesting to watch the under-canopy revolution evolve as controlled environments optimize. We may see opportunities for under-canopy lighting in greenhouses as supplemental lighting without top lighting or under-canopy lighting used when root temperatures are low. Maybe we’ll see stronger use cases from growers who grow other high-value bushy crops with dark sub-canopies. We can see a future ripe with opportunities to utilize efficient LEDs in novel ways to help growers be more productive in their space, and that makes us excited to be a part of it.

Note: Information for this story comes from JumpLights, Inc. a Maryland-based technology company that designs and manufactures LED lighting solutions for controlled environment commercial crop production. The company was founded with a desire to enable indoor farmers to use the latest technology to help produce a better crop yield and quality. JumpLights is a provider of innovative horticultural grow light solutions for indoor and greenhouse applications.

Matteo del Ninno is the Chief Technical Officer of JumpLights, Inc. See all author stories here.