Few climates allow for year-round outdoor grow seasons for cannabis. This leads cannabis cultivators to grow indoors. Cultivating cannabis indoors comes with its own set of challenges. One of the most important factors affecting the performance of indoor-grown cannabis is lighting.
High-pressure sodium (HPS) light bulbs have been the traditional light source used for growing cannabis indoors. As energy efficiency and consumption continues to be a concern for growers, light-emitting diodes (LEDs) are becoming more popular. We know LEDs are more energy efficient than HPS lights, but do they reduce photosynthetic performance and potency?
LED Lights vs HPS Lights for Growing Cannabis
A recently published study put both light sources to the test and here is what they found. First, three industry-standard LED lights were compared against each other.  Then the top-performing LED light of the set, the SPYDR xPLUS-Fluence by Osram, was compared against the ePapillion 1000 watt Double Ended HPS, an industry-standard HPS light.
Light effectiveness was determined by a mix of measurements. Light response curves were measured at several photosynthetic photon flux densities (PPFD) and carbon assimilation rates were tested. Tetrahydrocannabinolic acid (THCA) content was measured to determine potency.
Which Light is Better for Growing Cannabis Indoors?
The LED lighting was found to be the best for growing cannabis indoors when compared to HPS lighting. “Carbon assimilation rates displayed a 142% increase in plants grown under LED vs. HPS”.  The average photon flux densities for LEDs measured much higher than HPS. LED lights also increased amounts of THCA production by an average of 5.4%, suggesting LED lights improve cannabis potency.
This study shows LED lights do improve photosynthetic performance and potency in cannabis when compared to HPS. Initial costs of upgrading to LED systems can be expensive, which is what holds some growers back from upgrading. However, the investment has the potential to pay off over time in energy savings, and increased cannabinoid production.
 Jenkins, M.W. and Livesay, C.B. Photosynthetic performance and potency of Cannabis sativa L. grown under LED and HPS illumination. Agricultural Sciences. 2021;12:293-304. https://doi.org/10.4236/as.2021.123019 [Journal Impact Factor: 1.476; Times Cited: 1]
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