How intercanopy lighting increases the quality and yielding capacity of cannabis

cannabis loves light. In indoor grows, however, light can only easily reach the top of the plant due to the density of the leaves. Intercanopy lighting (IL) offers an innovative solution by distributing light more evenly so that it doesn’t only reach the top but also the middle and lower areas of the plant. This emerging technology has gained popularity in recent years, with numerous reports highlighting significant increases in both the yield and quality of cannabis.

Traditionally, growers have mimicked the sun when adding lighting to greenhouses and indoor facilities, hanging lamps above the plants from ceilings, roofs, or shelves (in the case of vertical grows). But, in indoor growing, the planting density is high and can cause unwanted shading from plant to plant and deep into the plant canopy (i.e. the top layer formed by the leaves and branches of cannabis plants).

Therefore, there may be a variation in light intensity at different levels that can reduce the plant’s physiological and biochemical processes, leading to a reduction in yield and quality because the plant is unable to reach its full photosynthetic potential. In the world of plant development, the leaves are effectively small biological solar panels. And, if you’ve invested energy into growing those solar panels but you don’t give them enough light, then that’s totally inefficient.

Furthermore, plant responses to light are highly localised. The use of higher overhead light fluxes to promote bud development in the lower areas can induce undesirable responses in the top colas, such as revegetation, foxtailing, or colour changes. In contrast, lower light fluxes at the top of the plants can lead to underdeveloped buds in the lower areas. This is why a big part of cannabis growing is focused on training the canopy, by pruning or defoliation, to maximise the penetration of light into the lower branches to obtain a more homogeneous crop.

Intercanopy lighting (IL) provides an alternative solution to these problems by moving the light directly into the lower canopy, where photosynthetic tissues are underused. This accelerates the development of flowers on the lower part of the plant. Growing cannabis with IL produces more grade A buds and less pruning residue, which increases the value of a specific crop by enriching its most valuable fraction. Besides, IL provides a way to increase performance by adding extra light without running the risk of negative responses from the upper colas, or having to make modifications to existing top lighting installations.

Studies support this lighting trend

One of the few people to study this intermediate field of horticultural lighting was the multinational Philips. More than five years of research into lighting strategies in cannabis cultivation has provided Philips and its customers with useful knowledge and ideas. For instance, extreme light levels above the crop (1500 – 2000 μmol/m2/s toplighting) generate higher energy costs, but don’t always produce the expected higher yields. And, just recently, they have confirmed that intercanopy lighting (IL) adds value, even with lower light levels.

“The entire plant benefits from that. After several crop cycles with different varieties, we determined that IL can achieve an average yield increase of 30%. As a result of the use of efficient IL LED lamps, the increase in biomass per kWh is uniform and even higher”, Philips claims.

Extra light among the foliage takes photosynthesis in the lower parts of the plant to a higher level. “As a result, there’s more energy available for the lower shoots and later flowers, which makes them develop more strongly. Amazingly, while we expected the lower inflorescences to benefit from the lower intercanopy lights, the top inflorescences also had a significant increase in yield compared to a control group. This was systematically repeated in several trials”.

The following photos illustrate the added value of IL for the main and side inflorescences of a THC- and CBD-dominant strain (without IL and with IL treatment in the same picture):

Despite differences in the design of these trials (light intensities, spectra, ratio between top lighting and intercanopy lighting), the results are very consistent: additional intercanopy lighting results in heavier, sturdy marketable flowers. The total yield (grams of flowers per m2) and the unit value (price per gram) also increase significantly with LED intercanopy lighting, which is exactly what cannabis growers are looking for.

More light or better positioned light?

But is the increase in yield due to the application of additional light and energy, or is this difference due to the position of the light in relation to the plant? Studies have also been conducted to determine the impact of redistributing the same DLI (same amount of energy used) between top lighting alone versus a combination of top lighting and intercanopy lighting.

Research carried out by the company StateHouse Holdings showed that the redistribution of a portion of the top lighting directly to the sides of the plants can lead to higher yields without the need for additional energy. Up until now, studies have been trying to understand what the best deployment of this strategy is (either on the canopy, below the canopy, somewhere in between…), and whether the benefits are as pronounced when working at high or low total intensities.

Another question driving this research is whether adding intercanopy lighting would help reduce labour (if there’s more flower development in the lower branches, not only does this increase yield and quality but also reduces the amount of defoliation required). Early indications show that the flowers below the canopy are of a higher quality than normal, and less pruning residue is produced.

In fact, from this research and other studies, they found that intercanopy lighting can help raise the grading of the flowers on the lower branches, meaning that buds that would normally be considered class B or C are now grade B or A. Put simply, the buds have a higher market value. In terms of quality and consistency, this is very good news. But not only is the quality of the buds increased, but the variability between the size and quality of the buds is also significantly reduced.

Conclusion

Intercanopy lighting systems have proven to be an effective tool for growers looking to improve their yields and flower quality in the lower areas of the plant, where light is often insufficient. If you’re a grower interested in producing more top quality buds whilst reducing pruning waste, intercanopy lighting may be the next big addition to your indoor grow.

With a yield increase of 20% or more, these complementary lighting systems stand out as an excellent choice, thanks to their extremely efficient design. And, as advances in horticultural lighting technology continue, the journey to understanding the implications and benefits of intercanopy lighting promises to be an exciting and fast-evolving frontier.

Photos courtesy of Cannabis Research Coalition and Philips.