It’s no secret that different plant growth stages require different lighting strategies. While nearly all research participants agree on the PAR levels needed during various growth stages, little consensus exists as to which lighting strategy is best for each stage.

While cultivators’ lighting preferences still vary, however, this year’s research showed an increase in the number of cultivators using light emitting diodes, a newer lighting technology more commonly referred to as LEDs: It is the only lighting technology to see double-digit increases during all growth stages between 2016 and 2018.

Growth Stage: Propagation

Nearly half (47%) of this year’s research participants said they use LEDs during the propagation period, compared to 21% in 2016. This represents a 26 percentage-point increase over two years. However, T5 (high output/HO) lights (or other HO fluorescents) are still used by a slim majority of growers (51%), compared with 65% in 2016 and 63% in 2017.

*Total may exceed 100% because respondents could select all that apply. **2017 results are based on the 294 research participants who grow only indoor and/or in greenhouses using supplemental lighting. 2016 results are based on 117 research participants who grow in indoor and/or greenhouses (with or without supplemental lighting) and/or outdoors.

Growth Stage: Vegetation

In vegetation, LED use was the most common among lighting types among research participants: 46% of growers reported using LEDs during this growth stage, climbing from 17% in 2016.

Nearly a third (32%) said they use quartz and/or ceramic metal halide (MH) lights during this growth stage—a drop of 11 percentage points from 2017. (CBT did not calculate net MH responses in 2016.)

T5s were the third-most popular lighting type—28% of respondents reported using them in this year’s study (down from 37% in 2016).

High-pressure sodium (HPS) lights also experienced a drop among growers during vegetation: a quarter (25%) of research participants said they use HPS lights in 2018 versus 31% in 2016.

Growth Stage: Flower

In flower, the research found that HPS remains the most-used lighting type in cannabis cultivation: 51% of growers said they use them, a 6 percentage-point lead over the next closest fixture, LED; 45% of growers in 2018 said they use LEDs versus 15% in 2016, a 30 percentage point increase during that period.

MH lights are less popular during flower than during vegetation: 11% of growers said they use either MH quartz or MH ceramic lights during this period (down 6 percentage points from 17% in 2017). (CBT did not calculate net MH responses in 2016.)

The LED Factor

Despite the data showing LED rise across the board, LEDs are still too expensive for some: 46% of 2018 respondents who do not use LEDs for the cannabis flowering stage (the only stage for which study participants were asked this question) and do not plan to within the next 12 months (or are unsure) cited initial cost as the main factor preventing them from converting (compared to 59% in 2017, no data for 2016).

More than a third (37%) still perceive the technology as unproven (down from 43% in 2017, no data for 2016), while more than a quarter (29%) of those not planning on adding LEDs felt the return on investment (ROI) was too long (28% in 2017, no data for 2016).

Despite some doubters, a third (33%) of growers who currently do not use LED technology during the flower period said they are planning on doing so within the next 12 months. In 2017, only 22% of growers who did not use LEDs during flower were planning on doing so within that same time period.