The Secrets of Light Deprivation for Greenhouses

The date is September 1, 2015. Although most outdoor cannabis growers are still a full month away from harvest, Mike Gibson is holding a beautiful, budding flower in the palm of his hand, freshly cut from a plant at his expansive Oregon grow op.

The flower looks great, as is always the case with Gibson’s high-quality Bubble Gum and OG Kush products. But when he first moved to Oregon, Gibson wasn’t happy with his results. He knew in his heart that his flowers could—and should—be more robust.

“Every time it came to middle of the flowering cycle in September, it was a little cold,” Gibson recalls. “So the flowers can’t expand and get that size they need, because they were flowering too late in the season.”

That’s when it hit him: light deprivation—i.e., tricking the plants into thinking that the season was changing earlier than it really was. That way, the buds would begin to expand during the warmer part of the grow season, resulting in big, chunky flowers come harvest time.

So Gibson built a light-dep greenhouse, 56 by 26 feet, in his quest to maximize the size of his dynamic, high-quality strains. “Knowing the genetics on my strains so well, I knew that if it was too cold in an indoor setting, the flowers wouldn’t get the expansion they need. They love a lot of warmth during their expansion time.”

But not too much warmth, he adds quickly: “If the temperature gets to 100 degrees indoors, the plants hate it. Yet if it’s 100 degrees outside, the plants are super-happy. At 100 degrees indoors, plants take a beating—they’re totally unhappy, and it messes up the final quality.”

Paul Filomena is the head of Luigi’s Farm, a leading consultation agency for large-scale cultivations. He too has been impressed with Gibson’s results. “Mike Gibson is the essence and embodiment of a master grower,” Filomena says. “I’ve seen a lot of product, and Mike’s is consistently in the top one or two. He’s perfected his Bubble Gum strain by creating the most optimal growing conditions.

“What I also love about it is that his flowers are grown organically rather than using any pesticides or potentially harmful products such as pyrethrins,” Filomena continues. “Instead, Mike makes homemade natural remedies with electrostatic water and citric acid or soap bark. I’ve had it field-tested by our associates, and it’s off the charts. Mike has mastered it to a level where he’s not sacrificing any elements of the grow or the quality of it.”

During winter, for example, Gibson takes advantage of the cold air outside by pulling it indoors during the final days of flowering. This causes the flowers to fill up with so much sugar that the rock-hard nugs ooze a clear syrup. “I felt like I’d cracked the code,” Gibson says with a smile.

Growers using light-deprivation greenhouses also take full advantage of the sun’s lumens. “Mike’s ability to manipulate environmental controls and grow multiple strains with exceptional trichome production puts him among the best in the industry,” Filomena asserts. “His high-yielding THC strains are perfect for extraction into cannabis oil and for research. What Mike has done is perfect the science and art of creating a product in a light-deprivation greenhouse that rivals any indoor product.”

Gibson has been growing commercially for more than 10 years. Originally from Southern California, he spent his teenage and early-adult years in Nevada, where he perfected his OG Kush and Bubble Gum strains, which are among the best in the world today.

Three years ago, Gibson moved to Oregon, where he set up an impressive operation featuring indoor and outdoor grows as well as a light-dep greenhouse.

Indoor growing can be a humbling experience, especially if you’re cultivating several different strains, which can exhibit extremely disparate characteristics and temperaments. Also, plants subjected to environmental stress—from such things as excessive heat or humidity, overwatering or a lack of oxygen to the roots, among other variables—can result in nutrient-uptake deficiencies, pest infestation, and a halt to THC production.

Gibson’s buds, on the other hand, display all the qualities of a superior product: their look and feel, the fullness of the flowers, and their smell and taste. “Taking his indoor experience to the outside has made Mike an elite all-around cannabis grower,” Filomena says.


Gibson’s approach to light-dep greenhouse growing is meticulous. First, he creates a custom mix for his medium, which includes 20 yards of composted dairy manure, 20 yards of coco, 10 yards of pumice, 200 pounds of crab, fish and seaweed meal, and 80 pounds of bokashi compost. Then he powders the plants’ roots with a soluble mycorrhizal formula containing multiple types of beneficial bacteria, yucca, humic acid and kelp during transplanting.

Next, he creates a raised garden bed measuring 45 feet long, with an inner trough 7 feet wide, using 70-pound straw bales, and fills it with his custom soil blend. He also installs a drip-emitter-style irrigation system.

By June 1, he’s ready to move his strains into the greenhouse, where he uses the 6-by-45-foot netting to support every “chunky beast” with ease. Then, on June 26, he forces his vigorous crop into flower.

At 7 p.m. each day, the greenhouse automatically deploys its cover to block out the sun, creating a completely dark environment. “If you do it manually, try to be exactly on time,” Gibson advises. “This way, your plants will never get confused.”

Once it’s dark out, though, he retracts the cover. “Most growers think you have to subject the plants to a full 12 hours of darkness to force them to flower,” Gibson explains. “Not true—by removing the cover immediately after the darkness sets in, you allow your plants to flourish in the lovely summer nights. Let them experience a natural moonrise and sunrise. The daylight at this point is already getting shorter every day. The plants will begin to flower instantly. It feels magical—‘presto change-o’ into flower,” he adds with a laugh.

A high amount of heat and moisture will build up in the greenhouse once it’s completely covered. “It can be very alarming, but my plants weren’t upset at all,” Gibson says. However, “if you were to leave the cover on for 12 hours, your plants will most likely mold.”

On August 29, Gibson’s plants are ready to harvest. “I simply squeeze my buds to check the firmness,” he says. He finishes them off with a gentle trim and an expert cure. The final result: super-chunky, dense and heavy flowers—10 out of 10 on the quality scale. In fact, the quality was identical to his indoor harvests, Gibson says, but the bud size was considerably larger: 24 plants that produced 83 pounds of tightly trimmed colas.

Genetic Advice for Light-Dep Growing

Don’t just throw any strain into a light-deprivation run and expect it to produce premium quality, Mike Gibson says. “Different genetics will respond better than others. This will be your biggest variable.”

From Gibson’s experience with light-dep, he’s found that some plants tend to have mold issues, while others have more trouble expanding in colder temps. “If you want to have A-grade product, your genetics are extremely crucial.”

Thanks to his adroit networking skills and his persistent efforts to obtain new genetics, Gibson’s strains have become top picks at local dispensaries. “Have a keen eye, but more importantly a keen nose,” he advises. Currently, his genetic arsenal boasts over 25 strains and hundreds of different phenotypes. And he’s always buying new seeds as well as obtaining prize-winning clones from fellow growers. “There is never a time when I’m not preparing for the next run,” Gibson states.

In order to keep all of his genetics alive, he uses a very detailed and laborious yet undeniably effective labeling system, from recloning to testing plants in indoor as well as outdoor runs. Along the way, he’s had to make heartbreaking decisions regarding which plants to keep and which to discard.

“After being in this industry so long, I still feel the most exciting part is popping the next seed open,” Gibson concludes. “I’ve said it before and I’ll say it again: You can be the best cannabis grower in the world, but your genetics are the key.”


  • So i to am working in central oregon and doing light dep but my question is how do i keep the pack rats from eating my plants. Help please


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