The Secret Of Maximizing your Harvest with Light Deprivation

Light deprivation, or “depping,” is a technique used by growers to maximize yield by manipulating light exposure to mimic light conditions that occur in the fall, which forces plants to flower. Until recently, growing cannabis inside was one of the safest options we had as growers. With legalization cascading across the country, what happens when growers no longer need to hide cannabis in their basements and need to increase the volume of their harvests?

Why is Darkness So Important?

Cannabis growers know darkness is as important as light. You may not think of the principles of yin (darkness) and yang (lightness) when planning your light deprivation schedule, but savvy growers understand the dual needs of cannabis.

Cannabis is a photoperiodic plant that responds to seasonal changes in light. That means when the days grow shorter, the plant’s life cycle is nearing its end, and flowering occurs for reproduction. In nature, male cannabis sacs release pollen to pollinate female plants in blossom. The result are seeds, which allow the plant to produce a next generation.

As a cultivated plant, cannabis still responds to light changes. Depending upon the strain you’re working with as well as your environmental demands, your light-to-dark ratio will vary a bit. If you’re new to the strain (or growing), talk to old hands about when to end the vegetative phase and trigger your plants’ flowering phase. That timing is critical to maximize your yield.

The Benefits of Light Deprivation

Farmers typically grow seedlings or clones under supplemental light to get a strong start, and then put them under light dep conditions to finish within two months. So long as they’ve got another batch of clones or seedlings ready to go into the ground, they can do it all again in time for fall.

  1. It can increase harvests from one outdoor grow to at least 4 or 5 a year.
  2. It significantly cuts energy consumption and total cost of your cannabis operation compared to indoor cultivation.
  3. It’s ultimately more sustainable for the planet.

Genetic Advice for Light-Dep Growing

Don’t just throw any strain into a light-deprivation run and expect it to produce premium quality.

By researching different strains, you gain critical information about sun exposure, when to plant and harvest, and vulnerabilities that could limit overall production.

Vulnerable strains include those most susceptible to mites, mildew, mold, root rot, and fertilizer sensitivities.

As you work through a few harvests, you’ll develop experience that will allow you to tackle more sensitive strains. Choose a strain, and master that strain. Figure out what it needs, how long it takes to flower, and how to reproduce those results.

Whatever strain you decide to work with, make sure to note ideal sun exposure and daily darkness minimums. This will vary depending on the plant type and whether it’s an eight-week or ten-week strain.

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Stick to Grow Schedule

In theory, covering your plants isn’t rocket science. However, there are some things to consider before you start out with your light deprivation grow project.

First, know that cannabis is very sensitive to light in the dark/night cycle during the flowering phase. Your precious ladies really want to be left alone, undisturbed, and in complete darkness during these hours. Sometimes, even slight disturbances from accidental light exposure can make them grow poorly, leading to all sorts of problems.

Covering your plants under some type of container or light-proof tarp with the sun hitting can increase temperatures and create a higher risk of moisture buildup inside. So keep an eye on these things as well. If you can, move your covered plants to a shady area out of direct sun.

To be effective, growers maximize the sun but shoot for a consistent light-dep schedule of twelve consecutive hours of unobstructed darkness for sixty days. Exactly how they accomplish this varies.

The old-school camp favors a sun exposure between 7:00 a.m. and 7:00 p.m., setting a hypothetical greenhouse covering time at 7:00 p.m. and uncovering at 7:00 a.m. This method is contingent upon good ventilation throughout the whole grow, especially during the bud cycle.

While a lot of people rely on the default 6:00 p.m. to 10:00 p.m. cover window that produces nice sticky buds, you have to figure out what schedule works best in your locale’s light, temperature, and humidity conditions. If that means covering at 5:00 p.m. and uncovering once it’s dark to let your plants awaken naturally when you do, so be it. If you’re in a hurry, you might cover at 6:00 p.m. and with a lot of ventilation, not uncover the plants until 7:00 a.m., shortening the duration 3 to 4 weeks.

It doesn’t matter whether you put a cover on your plants in the morning or the evening. But you need to be consistent and do this at the same time everyday so that your plants don’t get more than 12 hours of light. Once you start, you can’t change your schedule around during the light deprivation grow phase. Think about what works best for you; whether you want to do this in the morning or the evening.


Growers normally make use of light deprivation when they want to max out their harvests. It can be a game changer for a number of reasons. It’s a great way to get some money before the typical fall harvest. The technique can help facilitate two, and in some cases, three harvests per outdoor season. A popular method is to grow a group of plants the “normal” way, and cultivate a separate group using light dep. The light deprived crops can then be harvested as early as August while the other plants will be ready in fall.

Know that cannabis light deprivation may not work equally for everyone. The best way to go about it depends on various factors, including your local climate and your plant’s environment. This is why some experimentation with light dep can be worthwhile. In time, you will find a way to achieve optimal results from this technique.

[Updated, originally published 26.11. 2016]

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