First, the research explored the types of lighting cultivators are employing during various growth stages.
During propagation, T5s (or other high output (HO) fluorescents) are most commonly used, according to the data; 65% of cultivators say they use T5s at this stage of growth. (However, respondents were able to select multiple types of lighting, and the percentages for each type of lighting indicate that many growers are using more than one type of lighting during propagation.)
LEDs ranked second for use in propagation, with 21% of respondents saying they use this type of lighting at this growth stage.
In the vegetative growth stage, the most growers (43%) use metal halide lights: 23% say they use metal halide quartz lighting, and 20% use metal halide ceramic. (Again, based on the percentages for each lighting type, many growers indicated that they use more than one type of lighting during this growth stage as well.)
The next most frequently used type of lighting, according to the research, is T5s (or other HO fluorescents), with 37% of growers saying they use T5s in the veg stage. The other top-ranking lights used in veg are high-pressure sodium (HPS) (31%) and LEDs (17%).
During flowering, HPS lights are used most frequently – by 62% of cultivators. LEDs are the next most popular lighting type to be used at this growth stage (used by 15% of research participants).
All other lighting types are used by less than 10% of cultivators, according to the research data.
Some growers use no lighting during flowering (15%), vegetation (10%) or propagation (5%).
Three types of lighting — HPS, T5 and LED — were explored in the research for their use during any stage of growth, whether propagation, veg or flowering. HPS lights and T5 lights are used by the majority of growers (68% and 67%, respectively) during at least one growth stage, and LEDs are used by more than a quarter of cultivators.
Nearly three-fourths of greenhouse growers (71%) say they use supplemental lighting on their cannabis crops. The types of lighting varied, and again, growers’ responses indicate that they use various types of supplemental lighting during various growth stages, or possibly a combination of lighting at any particular stage.