Jessica McKeil   |   January 19, 2022

How to Harness the Darkness: A Practical Look at Light DEP for Cannabis Cultivation

Understanding how light deprivation, or light DEP, can affect cannabis cultivation.
Jessica McKeil is a cannabis writer based in British Columbia, Canada. She has a passion for cannabis tech and scientific breakthroughs, which has led her to work with some of the industry's biggest brands. She is the owner and lead-writer…

What is a light DEP system? When it comes to growing cannabis, it's all about applying the lighting techniques mastered within the indoor grow room to the great outdoors.

It essentially means using simple technology to force outdoor crops into flower, well before the days grow shorter in the regular fall harvest season.

Light DEP for outdoor growers can double annual harvests, reduce the risk of inclement fall weather, and reap mid-season profits.

What is Light DEP?

In most regions with a climate suitable for outdoor cultivation, growers can only manage one harvest per year. But, by installing light DEP technology, it's possible to double down to pump out two harvests in a single growing season.

Light deprivation, affectionately called light DEP by cannabis cultivators, is an outdoor cultivation technique that restricts the number of hours of light plants receives to trigger an early flower cycle.

This cultivation method requires simple technology, like a light-blocking tarp thrown over a hoop house. However, commercial operations may invest in more advanced mechanisms, like retractable blackout screens rolled over greenhouses.

How to Grow Light DEP Cannabis

If you are familiar with the light schedules used for indoor growing, light DEP uses these same techniques but outside. That means, instead of letting your plants naturally switch into flower with the shifts in season and daylight hours, you manually trigger it with light-blocking tarps.

During the vegetative stage, plants follow the sun's schedule. Around summer solstice, this could mean 16 hours of daylight (depending on region).

Naturally, the shorter fall days tell cannabis plants it is time to focus on flowering. But, with the light DEP technique, growers tell plants when to switch by covering the plants with a light-proof tarp.

The light DEP schedule for flower is 12 hours of light and 12 hours of dark, which is the exact schedule that indoor growers follow.

What Is a Light DEP Greenhouse?

Many commercial growers grow in light DEP greenhouses. Like a traditional greenhouse, it's a semi- to completely permanent outdoor facility that uses sunlight to grow but offers some environmental protections and climate controls.

The only difference is that light DEP greenhouses have a special, retractable blackout plant cover that envelops the greenhouse when growers want to restrict daylight hours.

There are even fully automated light deprivation greenhouses, but many growers rely on manual or power-assisted add-ons that pull the blackout greenhouse cover on and off as needed.

Yet, even home-growers can implement this technique without a commercial greenhouse. A light-blocking tarp thrown over simple hoop houses installed down each row works just as well, although it requires the grower to adhere to a strict schedule.

What is a Light DEP Strain?

Many factors influence strain decisions, including climate, market demands, availability, and cultivation techniques. Light DEP should also play into strain selection.

Ask your supplier or local breeder about the expected length of flowering and vegetative cycles. Strains with rapid and vigorous vegetative growth are ideally suited to light DEP, as it means larger plants in a shorter period. When you make the switch to flower, that translates into more bud.

Does Light DEP Increase Yields?

Technically speaking, light DEP yields per plant are lower than a more traditional outdoor cultivation approach. Because you are stopping the vegetative stage early, plants don't get as large and don't produce as many flowers as you'd expect from the usual sun-grown monsters.

However, if you take a step back and measure yields annually, there is a real possibility of increasing overall production.

Even if each harvest is slightly smaller, you'll get two crops per year. This will ensure a greater annual total of light DEP yields than you'd get while growing under normal seasonal conditions.

What's more, commercial growers usually stagger conventional outdoor crops with one or more greenhouses filled with light DEP plants. This means they have one set ready for harvest in summer and another ready in fall.

Final Considerations for Light DEP Cannabis Cultivation

If you choose to experiment with outdoor light DEP, there are a few final aspects that will require your attention: temperature and light leaks.

With the sun still high overhead, it can get quite hot within a blackout greenhouse. Therefore, ensure you monitor temperatures inside and use additional temperature controls to keep it within safe parameters.

You'll also need to test for light leaks. As with indoor growing, light sneaking underneath during the dark period can confuse plants and frustrate harvests.

But with these two potential hazards under control, light DEP gives the outdoor farmer an added layer of control. More control means more predictable harvests and increased annual profits.

 

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