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Light Deprivation (“Light Dep”) Techniques for Greenhouse Cannabis Cultivation

Light deprivation, commonly referred to as “light dep,” is a powerful technique used in greenhouse cannabis cultivation to control the photoperiod of plants. This method involves manipulating the amount of light your plants receive to simulate the natural light cycles of different seasons, thereby inducing flowering at specific times. Light dep techniques can help growers achieve multiple harvests per year, optimize yield quality, and improve overall plant health. Here’s a comprehensive guide on how to implement light dep in your greenhouse.

Understanding Light Dep Techniques

Light dep involves covering your greenhouse to block out light during part of the day, reducing the hours of light your plants receive. By controlling the light exposure, you can trigger the flowering stage of cannabis plants earlier than they would under natural light conditions. This technique is particularly beneficial for growers who want to produce high-quality buds outside the traditional outdoor growing season.

Benefits of Light Dep Techniques

Multiple Harvests Per Year: By controlling the light cycle, you can force your plants to flower multiple times within a single year, significantly increasing your overall yield.

Enhanced Quality: Light dep allows you to harvest during optimal conditions, avoiding the challenges of late-season pests, mold, and weather issues. This can result in higher quality and more potent buds.

Consistency and Predictability: With light dep, you can schedule your harvests more precisely, ensuring a steady supply of cannabis throughout the year.

Pest and Disease Management: Early flowering and harvests can help avoid peak seasons for pests and diseases, reducing the risk of crop damage.

Implementing Light Dep Techniques

To effectively use light dep techniques, you need to create a controlled environment that allows you to manipulate the light cycle. Here are the steps to implement light dep in your greenhouse:

Choosing the Right Greenhouse Covering

Lightproof Coverings: Use blackout tarps or lightproof fabrics specifically designed for light dep. These materials are durable, UV-resistant, and completely block out light when deployed.

Automated Systems: Consider investing in automated light dep systems that use motors and timers to deploy and retract the blackout coverings. Automated systems ensure precise light control and reduce the labor involved in manual covering.

Light Dep Schedule

Vegetative Stage: During the vegetative stage, cannabis plants require 18 to 24 hours of light per day. Ensure your greenhouse allows for maximum sunlight exposure during this period. Supplemental lighting may be used to extend daylight hours if needed.

Flowering Stage: To induce flowering, reduce the light exposure to 12 hours of light and 12 hours of darkness each day. Use the blackout coverings to create the necessary dark period. This change in light schedule will trigger the flowering hormones in your cannabis plants.

Managing Light Deprivation

Consistency: Maintain a consistent light dep schedule to avoid stressing the plants. Inconsistent light cycles can lead to hermaphroditism or reduced yields.

Timing: Ensure the blackout coverings are deployed and retracted at the same times each day. Use timers to automate this process for accuracy and convenience.

Ventilation: Proper ventilation is crucial during the dark period to prevent mold and mildew. Ensure your greenhouse has adequate airflow, even when covered. Use fans and ventilation systems to maintain air circulation and humidity levels.

Monitoring and Adjusting

Environmental Control: Continuously monitor the temperature and humidity inside the greenhouse, especially during the dark period. Sudden changes can stress plants and impact growth.

Plant Health: Regularly inspect your plants for signs of stress or disease. Light dep techniques can increase the risk of mold and mildew if not managed properly.

Adjustments: Be prepared to adjust your light dep schedule based on plant responses and environmental conditions. Flexibility is key to successful light dep implementation.

Harvesting with Light Dep

Staggered Harvests: Plan your light dep schedule to stagger harvests. This approach ensures a continuous supply of fresh cannabis and allows you to manage drying and curing processes more efficiently.

Quality Control: Harvesting under optimal conditions, such as avoiding high humidity and pest-prone periods, can enhance the quality and potency of your cannabis.

Challenges and Solutions

Manual Labor: Manually deploying and retracting blackout coverings can be labor-intensive. Solution: Invest in automated light dep systems to reduce labor and ensure consistency.

Ventilation Issues: Inadequate ventilation during the dark period can lead to mold and mildew. Solution: Use fans and ventilation systems to maintain airflow and control humidity levels.

Light Leaks: Even small light leaks can disrupt the flowering cycle. Solution: Regularly inspect your greenhouse for light leaks and repair any gaps or holes in the covering.

Light deprivation techniques offer a powerful tool for greenhouse cannabis growers, enabling them to control the photoperiod and optimize harvest times. By implementing light dep, you can achieve multiple harvests per year, improve the quality of your buds, and manage environmental challenges more effectively. With careful planning and management, light dep can significantly enhance your greenhouse cannabis cultivation experience, leading to healthier plants and higher yields.

Light deprivation can help outdoor growers control harvest and improve quality

Light deprivation can help cannabis growers looking to dial-in control, add more harvests to a production cycle and protect their plants from outdoor contaminants.

The technique, which involves using tarps or curtains to block out sunlight—typically in greenhouses or hoop houses—is growing in popularity as cultivators work to maximize production.

Light deprivation pushes cannabis plants to start the flowering process. To accomplish this, growers use shade cloth or other materials to allow in only 12 hours of sunlight, mimicking the amount of sun a plant would receive in a natural setting during the flowering phase.

“Every advantage a light-dep grower can eke out—lower cost of production, more harvests per year, something to mitigate the smoke damage—all adds to their long-term viability.

Increased harvests

According to the operation can be as simple as pulling a tarp over a hoop house at 5 p.m. and pulling it off again at 5 a.m.

In addition to light deprivation, that layer can partially protect plants from smoke, hail and torrential rain.

“The biggest advantage is adding a level of control to outdoor cultivation.

At High Life Farms in Chesaning, Michigan, Head of Cultivation light deprivation allows each room in his greenhouse cultivation operation to be harvested 51/2 times per year. With three flowering bays in the operation, High Life harvests between 15 and 18 times per year.

Newman’s greenhouses all use mechanical curtains in a fully automated system.

“It really helps to keep a more consistent environment like you would see indoors. “Even on cloudy days, we’re able to benefit from the sun.”

Newman likes to use Kush and OG varieties because they consistently finish at around 60 days and work well with High Life’s growing system.

According to Newman, the quality of cannabis grown outdoors using a light-deprivation system can be as good if not better than indoor-grown marijuana, as the plants receive extra UV rays from the sun, which helps them develop terpenes and cannabinoids.

Set schedule

Light-deprivation ensures that outdoor growers maximize the amount of time available for sun-grown cannabis and don’t fall victim to the weather, said of Humboldt, California-based Kristin Nevedal, chair of the International Cannabis Farmers Association.

She pointed out that a lot of cannabis growers in the mountains of Northern California get only one crop per year, so it’s important that it comes in on time. The set schedule offered by light deprivation also means that growers can plan around a definite harvest date and adjust their operation accordingly.

She agreed that cannabis grown with light-deprivation techniques can yield superior flower.

“It gives you an opportunity to produce very high-quality material,” Nevedal said.

She also prefers the way light deprivation allows growers to finish plants at a consistent size, say 3-4 feet, meaning workers aren’t struggling to take down much larger plants.

Using hoop houses with tarps can help ensure the plant doesn’t take too long to flower, which could put the harvest at risk for early frost, fall-season wildfires or rain and resulting moisture problems.

Nevedal said the growers with light-deprivation structures had additional protection against ash falling from wildfires that ravaged the West Coast last fall.

Labor efficiency

Dr. Jordan Lewis, CEO of Fotmer Life Sciences, a cannabis cultivation and extraction company based in Montevideo, Uruguay, called light deprivation a “fundamental tool.”

His team uses the technique in specially designed greenhouses with mechanical curtains to create two harvests where it would otherwise have only one.

Lengthening the harvest window allows Lewis to spread out the processing segment of the labor flow, cutting back on the need for seasonal labor and ensuring employees have enough work to stay busy.

Fotmer Life Sciences is growing in 18 different greenhouses right now, and the set schedule allows them to stagger the harvests, which helps with managing the labor needed for trimming and curing.

“We don’t have as many bottlenecks,”

He also points out that staggered harvesting is a risk-management tool: For example, shortening the life cycle of the plant by adjusting the light can help to prevent contamination between batches.

“The shorter the life cycle of the plant, the less opportunity (there is) for disease to be impactful.

Another tip: Light deprivation does not permit a lot of room for error. A pinhole of light getting through a curtain can cause plants to herm and go to seed, ruining the whole crop.

“You have to make sure there’s no light, or you don’t get the results you need.