48 Hours of Dark vs. 48 Hours of Light: Dr. Bruce Bugbee Weighs In On Optimizing Lighting for Quality
As a hobby grower, I have heard countless growers encourage extended periods of darkness as a tool pre-harvest to increase quality.
The idea — while, admittedly, very broscience-y — is that doing so at the final stretch lets the plants know that it is almost the and to “give it all its got” for one final chance of reproduction.
Due to the lack of evidence, I’ve always taken this advice with a grain of salt, which is why, when I saw Dr. Bugbee — one of the nations leading lighting researchers — weighing in on the topic in a recent YouTube interview, I had to tune in.
6 Key Points From Bugbee’s Interview on Pre-Harvest Lighting:
- Photosynthetic energy is used to synthesize sugars that are used to make terpenes and trichomes.
- No lights = no new energy = plants are not synthesizing new terpenes and trichomes in the dark.
- During dark periods, plants consume accumulated sugars from the light periods.
- Cold temperatures reduce the volatility of terpenes, which preserves existing terpenes (but slows down synthesis of new terpenes).
- Could be the decrease in temperatures, not the lack of light, that is having the observed effect on overall quality of harvest.
- The opposite extreme of 48 hours of darkness would be 48 hours of lights on but at a reduced temperature to protect/preserve existing compounds.
Bugbee’s take: “We ought to put more emphasis on continued synthesis of terpenes right ‘till the last day of harvest, and less emphasis on doing something to preserve what’s already there.”
