At High Level Health in Denver, Lead Grower Chaz Kobayashi places a priority on mimicking natural lighting cycles and intensity, as well as on each cultivar’s geographic origins, he says, to get the most of our his plants.
Each plant at High Level Health’s two facilities starts out under very low-intensity light before the vegetative state, says Kobayashi. Four-inch clones soak up full-spectrum LED lights from Transcend Lighting, but only up to about 300 or 400 micromoles (PAR rating), or 150 to 200 photosynthetic photon flux density (PPFD), which is the measurement of light used for photosynthesis. .
“I use low intensity … [because] they need less light,” he says. “But they’re very sensitive to environmental swaying. LEDs help us keep the canopy temperature cool and also give us the PAR rating we need.”
From there, the plants move to veg rooms under (depending on the strain) mostly 600w metal halides (though Kobayashi is testing some full spectrum LED lights as well). Next, they move to the bloom rooms, where he places them under single-ended or double-ended Gavita lights with Ushio or Eye Hortilux HPS bulbs. Also, depending on the strain, the lights are placed closer to or farther from the plants.
“In the end, anywhere from a week-and-a-half to a week out, we change it out to our UV bulbs to finish,” he says.
That change in wavelength and distance is part of a larger plan to modify the terpene profile by using the lighting and environment to trigger programmed cell death in the plant and boost terpene production. This can be done by lowering the plant temperature and the lights, but either option on its own won’t “bring it to the best place for terpene profile and THC content,” Kobayashi says.
For example, with High Level Health’s Biostar strain, which tests at 33 percent activated THC, completing the growth cycle with the UV lights closer to the plants will produce more THC. But the smoking experience isn’t as good because the terpene content declines, so Kobayashi reduced the lighting intensity.
Finding the Right Balance
Kobayashi aims to find the ideal balance to produce the highest-quality smoking experience. “It’s finding that perfect [light] height, where it’s not damaging the plant too much, but it’s putting enough stress on it so that the trichomes start overproducing and trying to protect the plant,” he says.
Finding the right setup for specific strains requires trial and error, but using clues from each strain’s natural environment can provide a starting point for light intensity and duration the plant is genetically programmed to thrive under, he says.
“Indica plants have big, broad leaves for a reason,” says Kobayashi. “In those areas that they grow, water and nutrients aren’t as available as elsewhere. [The leaves] have to store water, or they have to have big solar panels [the leaves themselves] to intake light because they’re underneath a deciduous forest.”
But sativa strains that grow near the equator have constant access to nutrients and water. Genetically, they started making thinner leaves that had more light accessibility. “These are all things I take into account when I’m thinking about what light a plant needs,” he says.
For hybrids, the process is more difficult, but that makes keeping a close eye while experimenting during growth even more important. For example, some cultivators may struggle to grow Girl Scout Cookies because they treat the strain the same as the other plants. With some experimentation, Kobayashi and his team discovered that keeping the light farther away and less intense from start to finish produced a healthier plant.
“The common belief is that more light equals bigger plants, but there are a lot of case studies coming out about the way plants really use photosynthesis,” says Kobayashi. “What they’re finding … [is that] plants are actually going into a rest mode while lights are on because the plant ends up shutting itself down as a defense mechanism toward too much light.”
The natural movement of light begins more softly and includes two to four hours of intense, overhead full-spectrum light before dimming down, he says. For Girl Scout Cookies, when a grower puts the plant under more intense light, similar to “a heavy-drinking hybrid,” the plant will spread out and look thinner, Kobayashi says. But if you decrease the PAR and increase distance by about half, along with lower water and nutrient intake to match, the plant should grow fuller.
Experimentation doesn’t mean random trials for Kobayashi. He uses a PAR meter to determine how much photosynthetically active radiation is available for photosynthesis. In fact, he brought his PAR meter to the Marijuana Business Conference, where he tested new lights on site before bringing home California Lightworks and Spectrum King lights for trials.
He also uses a temperature gun to gauge the heat reaching the leaves. Surface temperature is important, since having intense, direct light on a plant can raise the temperature to a point where it’s working against the plant’s health, even if it’s the correct distance away, says Kobayashi. “Let’s say you want to get up to 1,000 micromoles (500 PPFD). That’s where the plant wants to be,” says Kobayashi. “But by bringing it to 1,000 micromoles , now we’re at 100 degrees canopy temperature. … Then it’s better to get less light intensity to have a better … canopy temperature and … health.”
Armed with those tools, Kobayashi works with his automation systems daily to watch for changes among plants during testing. Then, he uses the new information, plus guidelines he’s developed from the plant’s genetics, to make modification decisions. “When you feel like a plant is acting more like an indica, we’ll go with less light. … Then we see how it reacts,” he says. “Is it drinking less? Is the stacking of the blossoms becoming tighter or less? ... Is it losing chlorophyll from the top down? That’s where the trial and error and, really, the human aspect comes into play.”
Planning for Growth
Planning became more important for Kobayashi as the High Level Health facilities expanded. When it was a 30-light grow, not as much thought was given to the layout of lights and plants. But with four 70- to 100-light grow rooms in one facility and three 40-light grow rooms in another, the stakes are much higher. Running multiple strains in the same grow rooms means monitoring lighting and the plants’ layout to optimize the growing environment.
Each grow room is mapped out with which strains are under which lights, including how many plants are placed per light. The map allows workers to know at a glance where to find a particular strain and what the surrounding environment looks like.
The planning continues with testing out new ideas, as well. As the grow has expanded, the consequences of any mistake have multiplied. Though Kobayashi makes small changes on his grow from day to day, larger shifts in his approach can take months or even a year before moving from a trial area to the grow room.
But the information he’s collecting about how each strain reacts to a change in light intensity or temperature helps him build plans for lighting changes that will lead to improved results.
“I have a SOP (standard operating procedure) book with every strain we have, the way it grows and certain notes about its details,” Kobayashi says. “It’s not perfect, but in the end, that’s going to get us closer to the area where, if we have a question about a plant, what to do with its light or what spectrum, we have past details for it. Hopefully, we can get the details down with a curve, a specific spectrum and a specific temperature drop that correlates with that curve.”