The most common way of using lighting in cannabis cultivation is top lighting – we've all seen those flashy cannabis facilities with hundreds of lights hanging above the tops of plants. Recently, under-canopy lighting has emerged as a new way of redistributing light and solving the issue of lower-canopy buds, which are usually not of the same quality as those at the top of the plant. If one looks at tomato growers, however, one may notice that they use a third method: inter-canopy lighting (or ICL for short). Dominique van Gruisen from Innexo asked himself: "Why not do this in cannabis too?"
Lighting from the side
Cannabis and inter-canopy lighting was the first major research trial that Innexo carried out in 2022, in collaboration with Fluence, to determine how the redistribution of light would impact cannabis in terms of yield quality and secondary metabolites. "We started the trial design 1 year prior to the execution, doing all the prep work, getting all the details right. It was a tightly controlled trial with a lot of data," Dominique explains. "In this trial, we used 66% top light and 33% inter-canopy." Once again, inter-canopy lighting is not to be mistaken for under-canopy lighting, as the latter has lights facing upward, while inter-canopy lighting faces sideways. "The results from that trial were super interesting. We saw that not only did we not get a reduction in yield, but there was an increase in quality. The usual C-grade buds at the bottom of the plant turned into A and B grade buds that hold a higher commercial value. We basically had only sellable flowers."
While certainly insightful, the results didn't seem to show much difference between inter-canopy and normal top lighting in terms of yield. It's exactly here that things got really interesting. "After that trial, I thought, let me do an experiment from the energy-saving standpoint. Instead of doing 66% top light and 33% inter-canopy, I did 50-50. What I saw from this trial was not only that I got the same quality results as the former trial, but I also achieved 15% more yield using 30% less energy, because inter-canopy fixtures are lower in wattage than top lights. Since inter-canopy lighting is closer to the plant, there's a higher PPFD on the leaves." Then, Dominique went all in. "I wondered what would happen if I went 100% inter-canopy." This was the next experiment.
Comparing the results with the control group, he achieved the same output with 100% inter-canopy but with 50% energy savings. "Less energy, same output. Not only that, but the way energy flows in the plant also ensures that the top flower still develops and blooms properly even if it doesn't get direct light. These trials tell us a bit about the energy metabolism of this plant."
ICL with long-flowering varieties
To push the envelope even further, Dominique decided to try this lighting technique with long-flowering varieties – such as landraces. "I thought that if you could do this in a greenhouse, you are basically unlimited in terms of vertical growth, and if you redistribute the light so that the sides of the plants are illuminated, you can possibly increase the yield in the vertical lane. Just like in tomatoes, you make use of the verticality of the greenhouse and don't create a two-dimensional canopy." Obviously, not all varieties are suitable for this, and Dominique is very candid in saying that landraces and stretchy long flowering varieties lend themselves well to such a method. "I found out that I can get the same yield per m² surface area as in normal top-lighting commercial settings with landrace varieties, while saving energy because of the lower wattage of inter-canopy lighting. This is also ultimately great for patients because landrace varieties have a combination of cannabinoids and terpene profiles that are all but lost in modern varieties."
Now, the next step in cannabis inter-canopy lighting is to come up with light mapping, "which should not be too difficult when you use inter-canopy lighting only." The combination of this light distribution methodology, coupled with the no-veg method Dominique and Innexo developed, can greatly reduce cycle times as well as labor and energy consumption. "With all of that together, we can achieve energy reductions of up to 70%, and get the same yield – if not improved – and a much more consistent flower quality."
In a market that is getting increasingly competitive, having such an advantage can be crucial for growers. "There's so much innovation in cannabis that will be adopted by other crops later on," Dominique says. "We as an industry are not giving ourselves enough credit if we think cannabis growers have a lot to learn from other commercial horti spaces. Of course they do in terms of standardization and consistency, but in terms of new tech, cannabis is head and shoulders above all other crops. Cannabis is poised to be – and always has been – a crop leading in innovation. We need this tech to improve consistency for pharmaceuticals coming from plants, generally speaking. For that, we are now looking at a model plant, and if we nail cannabis, we can basically do this with every other crop."
For more information:
Innexo BV
www.innexo.nl