This is worth watching to the end and taking notes, as it summarizes the current state of the art for weed lighting:
Some takeaways from this interview, keeping in mind that Bugbee’s answers are informed by 7 straight years of university-funded cannabis research:
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2-10% blue photons is optimal across the whole weed plant lifecycle (use less blue the less far red you have). Most current LEDs have way too much blue
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There are no cannabinoid or terp increases found from using more blue or UV, and they’ve tested it dozens of ways with UVA, UVB and violet but can find no gains at all
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Green photons are great for plants, but not safe during night cycle - weed can get photoperiod disrupted by as little as 3x the brightness of the full moon
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Red photons do not encourage stretch in veg, but far red does…mitigated by blue and high ppfd (he’s previously noted that stretch after flip to flower is mostly driven by genetics, not spectrum)
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10-20% far red photons is optimal (use less far red the less blue you have). Most LEDs have way too little far red
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Far red is really good for early veg growth (filling in spaces, makes plants grow wide) and flower development, not as good during late veg unless mitigated by enough blue
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Neither far red nor deep red speed up flowering or put plants to sleep faster, both are popular myths not supported in any research findings, and they’ve tried many experiments to test this
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Weed can take 1000ppfd as a seedling, but any more than that requires CO2 supp
(no more than 43 dli for veg or flower, in general, unless you’ve got optimal everything) -
Weed leaf CO2 saturation is 1200ppm and it can’t use higher than that, but at least CO2 is cheap…cuz it makes a difference!
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Weed supplemented at 1200ppm CO2 has 30%+ faster growth if everything else is optimal, and their general rule is 50% faster growth = 30% greater yields (20% more stem growth, harvest index goes down), so CO2 supplementation makes a huge difference in yield for the cost
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cannabis cannot use 24hr light, and it becomes less efficient with long photoperiods after 18hrs, and benefits from a break of 4-6hrs during veg
I hope this information helps people use and recommend better LEDs for lighting builds.
