As medical cannabis or medical marijuana becomes legalized in more regions around the world, this represents an exciting new market for growers. But how do you get the best results when growing this crop in a greenhouse under LED lighting? Signify Plant Specialist Sabrina Almeida de Carvalho is carrying out several trials with research partners. In this blog, she answers the question based on research in collaboration with Wageningen University & Research: Will medical cannabis flower with LED lighting?
Will medical cannabis flower with LED lighting?
Critical factors for inducing medical cannabis to flower
The simple answer to the question above is: ‘Yes, medical cannabis will flower when grown with LED lighting’. How much and how fast is a bit more complex. Medical cannabis plants are triggered to flower according to their photoperiod, which simply means the number of hours of light they receive. In general terms, plants like medical cannabis need to be in full darkness for at least 12 hours and sometimes longer, every day.
For plants like chrysanthemums and medical cannabis, we even talk about the ‘critical night’. They must go through a dark cycle to guarantee flowering. We’ve known this about medical marijuana since the 1910’s, thanks to studies carried out by Julien Tournois1 and B. Thomas2 on the light-darkness effect with hop and cannabis plants. In the 1970’s, Salisbury and Roos3 also documented their results with growing cannabis plants. It doesn’t matter what kind of light – sunlight, high pressure sodium (HPS) or LED lighting – the medical marijuana plant receives during the day, where the plant is in the growth cycle or, what light intensity medical marijuana plants are exposed to during the daytime, they will flower if they receive at least 12 hours of full darkness.
Flowering occurs with both HPS and LED, if the plants get at least 12 hours of full darkness
Set-up of trials
I investigated several trials that are being conducted to grow medical cannabis crops under LED lighting in a greenhouse and in a vertical farm. Flowering is the third growth stage for medical cannabis. This is arguably one of the most important stages, because it triggers the production of buds and cannabinoids or terpenes. So, there would be no point in growing medical cannabis with LED lighting if it couldn’t flower.
The pictures below show crops from the trials. Each trial used different lighting spectra, but all plants flowered if their 12-hour ‘nights’ were respected.
Images from trials which all had different spectra. All situations flowered and achieved similar to higher yields compared to conventional set-ups.
More energy efficient, high intensity lighting source
What I find the most exciting about these results is that the impact of light is the definitive factor and that it doesn’t matter whether it’s HPS or LED. The great benefit of using LED though, is the fact that LEDs are more energy efficient and allow higher intensities of lighting to be applied to crops compared to HPS lighting. The trials also show that growers who use LED lighting can expect to produce 1 extra crop cycle a year for medical cannabis, while using energy very efficiently.
Follow our research to find more answers
In our long-term research collaboration with Wageningen University & Research (WUR), we are investigating how LED grow lights can influence compound production, quality and plant characteristics of cannabis crops grown for medical purposes. The research results will support growers in creating the ideal growing conditions for medical cannabis. Read more about the scope of the research in our press release and follow the Horti blogs from Signify on growing with medical cannabis to read results as they become available.
- Tournois J. Études sur la sexualité du houblon. Annis. Sci. Nat. (Bot.). 1914;19:49-191.
- Thomas B, Vince-Prue D. Photoperiodism in Plants. Academic Press. London. 1996.
- FB Salisbury, CW Ross. Plant physiology, 2nd ed., Wadsworth Publishing Comp., USA. 1978.
Sabrina Carvalho is a Plant Specialist for the biobased segment at Signify Horticulture LED Solutions. She has a background in academic plant research, and she now applies that knowledge to translate scientific information and research performed at Signify into value for growers. She has collaborated with researchers, innovators and growers, not only to develop and improve Philips LED lighting technologies, but also to find new and innovative ways to study plants.
Why grow with LED?
High sustainable production
Growing your cannabis with the use of LED will generate higher yield per square meter compared to growing with other light sources. The right light optimizes photosynthesis and flower production and improves your numbers. Furthermore it uses the lowest possible energy input with a maximum production per Watt, a minimal use of water and nutrients, and a great working environment.
Raise the quality and predictability of your cannabis crop.
By using LED light, the climate in your greenhouse or sole source facility can be controlled more easily. LED light comes with hardly any heat; thus the climate can be steered more easily. This results in consistent quality with the right composition of compounds; the same quantity year-round to simplify logistical planning and guarantee reliable manufacturing.
By using a dedicated light recipe for cannabis, plant characteristics can be steered. You can steer certain specific compounds meeting your customers requirement and differentiate yourself in the market.
Learn more about LED lighting in horticulture by reading our latest articles and case studies.