Researchers discover how twilight-toned lighting can grow more potent pot while saving energy.
A team of Australian researchers has discovered that giving medicinal cannabis plants a dose of twilight-colored light can boost their potency—and cut electricity bills.
In a new study published in Scientific Reports, scientists tested how far-red (FR) light—the faint, sunset-tinted wavelengths just beyond red on the color spectrum—impacts the growth and chemical makeup of cannabis. Their goal: to reduce the usual 12-hour daily light cycle to just 10 hours without sacrificing yield or quality.
What they found could change the way cannabis is grown indoors.
“The results are striking,” said lead author Tyson Peterswald. “With just two hours of far-red light added after a shorter day, we saw a 70% increase in THC yield in one of the strains.”
What Is Far-Red Light—and Why Does It Matter?
Far-red light (700–800 nm) naturally dominates during sunrise and sunset. In nature, plants interpret more FR light as a sign they’re in the shade and respond by growing taller to reach sunlight. But there’s a twist: when combined with standard red or white light, far-red can actually improve photosynthesis—the process plants use to turn light into food.
This effect, called the Emerson enhancement, helps plants photosynthesize more efficiently when different wavelengths are balanced just right.
The Experiment: Shorter Days, Smarter Light
The researchers used three cannabis strains—Cannatonic (high in CBD), Hindu Kush, and Northern Lights (both high in THC). They exposed the plants to six different lighting setups, including:
- Standard 12-hour full-spectrum light (control).
- 10-hour full-spectrum light with no FR.
- 10-hour full-spectrum light plus 2 hours of far-red (after dark or at end-of-day).
- A 4-hour FR treatment split between light and dark periods.
The Results: THC Up, Energy Down
In Northern Lights, adding 2 hours of FR light after a 10-hour day (called “10L_2D”) led to a 70% increase in total THC yield compared to the standard 12-hour setup—despite using less full-spectrum light. Hindu Kush also showed a THC increase with 4 hours of FR, though results varied by strain.
Meanwhile, shorter light periods led to 5.5% energy savings—a significant cut for power-hungry indoor grow operations.
But it wasn’t all good news. Overdoing far-red (like adding 4 hours to a 12-hour light cycle) delayed flowering and reduced flower biomass, highlighting the delicate balance growers must strike.
Why It Matters
Indoor cannabis farming is energy-intensive—sometimes requiring over 5,000 kWh of electricity per kilogram of dried flower. With lighting making up nearly 40% of that usage, optimizing light schedules isn’t just good science—it’s good economics.
These findings suggest a win-win: growers could increase potency while reducing lighting time and carbon emissions, especially in high-THC cultivars.
Still, the benefits were highly strain-specific, so commercial growers would need to test lighting strategies on their own genetics.
The Bigger Picture
With cannabis legalization expanding and sustainability becoming a top priority in agriculture, precision lighting could be the next big leap for controlled-environment farming. And with this study, far-red light just might earn a permanent place in the cannabis grower’s toolkit.
Across the cannabis research landscape, new findings are rapidly reshaping how we understand both the plant and its impact. For instance, recent studies suggest CBD may help slow memory decline in Alzheimer’s patients (read more). In Germany, hemp fields are becoming unlikely havens for endangered birds like the marsh warbler (read more). Meanwhile, data from Switzerland shows that legal access to cannabis reduces problematic use among young adults(read more). Together, these discoveries reflect a growing ecosystem of evidence supporting smarter, science-backed cannabis policy and practice.
The Cannex recommends: where to buy Northern Lights
