Light deprivation, aka light dep, is a technique for increasing the number of annual harvests for flowering plants. If you do it right, you can count on three harvests per year instead of one. Some growers have boasted four or five harvests using this technique!

If you live in an area that gets a lot of rain in autumn, your plants could be vulnerable to bud rot and mold. Some growers solve this problem by growing auto-flowering strains. These tend to bloom more quickly than other strains regardless of light cycles.

Another way to solve the problem is to use the light dep technique and have the girls blooming in July.

The benefits of light dep don’t stop there. Compared to traditional indoor growing, outdoor light dep uses roughly half as much electricity per ounce of bud.

Even indoor light dep lowers electrical costs because you’re not running your lights as much.

How does Light Dep Work?

Light dep involves tricking your plants into flowering early by controlling the lighting schedule. Growers normally do this in greenhouse grows using special covers for the greenhouse. You can also use this technique indoors.

Some plants in the vegetative stage need 13-16 hours of light each day to remain in the vegetative stage. A lot of indoor growers keep the lights on for 18 hours or more daily.

When it’s time to induce flowering in a traditional grow, the light hours drop to 12 or less. This mimics what outdoor growers like to call “late summer” or “early autumn.” Strains that do not auto-flower take this as a cue to start producing buds.

When you have a light dep grow, you drop your light hours to 12 or less early in the season. This shortens your vegetative stage and induces early flowering. Read our How to Guide for the Final Two Weeks, to learn how to increase yield other ways too.

How to Perform the Light Dep Technique Indoors

The key to pulling this off is always going to be creating a 100% light-proof environment.

Indoors, this could mean finding a good grow tent. Gorilla Grow Tents are the most durable, and they’re great at keeping light out.

If you want to use a grow room without a tent, you will need to seal your windows and anything else that allows light to come in. Use thick sheets of light-proof plastic. Alternatively, use blinds and curtains if you’re sure they can keep the room 100% light-free.

You can also find some light-proof plastic bags that can fit over individual plants and their growing containers. This will require clamps. Clothes pins are good for this.

The problem with putting each plant in a bag is that you have to remove the bags or the grow lights will be useless when it’s time to turn them on.

Another problem is that you may not know how big each plant will get. This means that you won’t know whether your bags are too small until it’s too late.

However you do it, just remember: Zero light. 12+ hours. No interruptions. Even a couple minutes of light here and there during the dark period can cause problems in your buds.

How to Perform the Light Dep Technique Outdoors

You will need some type of structure. This could be an outdoor tent, a greenhouse, or scaffolding.

You must be able to cover it with 100% light-proof materials.

For greenhouses, hoop houses, and other large structures, we recommend 50'x100' Black & White Woven Blackout Light Deprivation Film. This stuff is light-proof and waterproof, and it’s 9mm thick.

Some growers use tarps to cover the structures.

Warning! Do Not Change Your Lighting Schedule!

When you begin the dark period doesn’t matter nearly as much as being consistent. Do it at the same time each and every day or you’re gonna trip out your plants and ruin your grow.

Like old ladies who go to bed at 8pm every night and wake up at 4am every morning to a rerun of Murder She Wrote, your girls want a wholesome and regular schedule.

Automate Your Light Deprivation

You can buy an automated light deprivation greenhouse. This is the most expensive way to automate the lighting schedule.

Less expensive, but not cheap, are light deprivation greenhouse conversion kits.

Before exploring these options, check your municipal or county building codes.

Other options include automated curtain systems for grow rooms and greenhouses.

All of the above will free you of the responsibility of being there to install or remove your light-blocking material every single day at the same time each day. It’s not something you can train your dog to do.

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