To understand spectrum tuning, you first, want to understand how different color spectrum can
effect plant growth. The most studied colors that effect cannabis growth are by far blue and red.
Blue Light:
Vegetative Stage: Blue light (400-500 nm) is essential during cannabis’ vegetative phase. It
promotes strong root development, thicker stems, and bushier growth by influencing chlorophyll
production and regulating stomata (leaf openings). Studies have shown it can even increase
THC concentration [blue light and THC – Magagnini et al., 2018].
Red Light:
Flowering Stage: Red light (620-740 nm) plays a key role in the flowering stage. It triggers bud
development, increases flaower size and density, and influences cannabinoid production. Studies
haven’t necessarily shown it produces the highest overall yield, but it can impact the quality and
potency of the flowers.
Balancing the Light Spectrum:
Growers typically use a combination of blue and red light to optimize cannabis growth
throughout its lifecycle. The ideal ratio depends on the desired outcome: bushier plants in the
vegetative stage might require more blue light, while maximizing flower production during
flowering might involve a higher red light ratio.
Grand Master LEDs Taratula Borg and spectrum tuning:
The Borg has 4 drivers (or channels) that, through dimming each independently, all the
spectrums are produced.
The four channels are :
- Channel #1 Cool White: This is a base white spectrum with added Blue (think Metal Halide).
- Channel #2 Warm White: This is a base white spectrum with added Red (think High Pressure
Sodium) - Channel #3 660nm Red: This is straight Red usually used in the flowering stage.
- Channel #4 Far Red: Utilizing the Emerson Effect, creates more efficient photosynthesis.
Using the Grand Mater Controller or manually setting each of the four channel dimmers is how
each spectrum is achieved.
For example, a good overall vegetative spectrum can be achieved by either selecting preset #6
on our controller (our Master 6 veg spectrum) or setting the Cool white channel to 100%, the
Warm white channel to 30%, and the last 2 channels to 0%
A good overall Flowering spectrum can be set with preset #49 (our long leg spectrum) or by
custom setting channel 1 to 60%, channel 2 to 100%, channel 3 to 25%, and channel 4 to 60%
Recommendations
Seedling Stage: During this stage, plants primarily require blue light spectrum (400-450 nm).
Blue light promotes strong root development and stem growth.
Vegetative Stage: In this stage, plants need a balanced combination of blue and red light
spectrums.Blue light (450-490 nm) continues to be important for photosynthesis and maintaining
a compact plant size.Red light (630-680 nm) promotes stem and leaf growth.
Flowering Stage: During flowering, plants require more red light and some blue light.
Red light stimulates the production of flowering hormones, which is crucial for the plant’s
reproductive stage. Adding 660nm to the base spectrum here helps move the spectrum towards
the red side. Far Red added in conjunction with the 660nm red can create the Emerson Effect.
PPFD Recommendations
Photosynthetic Photon Flux Density = Intensity of light hitting the canopy
Seedling Stage (1-2 weeks old): Seedlings are delicate and require a gentle light environment.
Aim for a PPFD range of 100 to 300 μmol/m2/s. Exceeding this range can stress or damage the
young plants.
Vegetative Stage (3 weeks – flowering): During vegetation, cannabis plants focus on building
strong roots and stems for a productive harvest. Increase the light intensity to a range of 400 to
700 μmol/m2/s. Some growers push it even higher, up to 1000 μmol/m2/s, for potentially faster
growth, but proper ventilation or CO2 supplementation and temperature control become crucial
at these levels.
Flowering Stage (flowering – harvest): This is when light intensity plays a key role in bud
development and cannabinoid production. Aim for a PPFD range of 600 to 900 μmol/m2/s. Some
growers experiment with even higher intensities (up to 1500 μmol/m2/s) for potentially bigger
yields, but again, proper airflow, CO2 supplementation, and temperature management are
essential to prevent stress.
Things to Consider
Far Red (channel 4): Far red should be used the entire flowering cycle. Far red in the
spectrum in conjunction with 660nm red will drive more efficient photosynthesis than just 660nm
red alone. Far red at higher levels can cause shade avoidance and stretching in plants so we
recommend to stay no more than 10% of your total spectrum in far red to avoid this. The ratio of
660nm red to Far red matters here as well. If you have more far red than 660nm red that too will
trigger stretching, or shade avoidence. Some growers are keeping far red channel on (channel
4 only) after the light period ends for 15min to signal the dark cycle has begun to the plant
earlier. There has been some evidence of faster flowering times (as little as a few days to as
much as 14 days sooner) using this method.