What is Light Dep? advanced outdoor techniques

When you’re getting started as a grower, the first consideration is always “outdoor vs. indoor. Once that’s decided, there’s more to consider for maximum quality and yields while reducing the cost and carbon footprint of your greenhouse or outdoor grow. With our grow bible, you can immediately use techniques like light deprivation, more commonly known as “light dep,” to speed up your outdoor grow. 

Growing light dep cannabis plants taps into the plant’s sensitivity to changes in light hours to flip from the vegetative stage to the flowering stage (photoperiodism). Using this technique, outdoor growers can choose to force the plant to flower earlier than it would have done on its own.

The light dep technique isn’t all magic, though. There are a few downsides to consider. But overall, it’s a great tool to be aware of when using a greenhouse or outdoor grow. 

How does light dep work? 

With the light dep technique, you can bring the control of artificial lighting that indoor growers have outdoors. It lets you decide when plants flower instead of waiting on the seasons to change. It might take some extra diligence and adherence to a schedule or an automated system, but it can be worth the effort.

In a typical outdoor grow or greenhouse, your plants will start to flower when the days become shorter at the end of the summer or, in the case of autoflowers, automatically. If you don’t live in one of the prime locations for cultivating cannabis, this may not be an option, as fall can bring bad weather in many regions. 

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By using shades, tarps, roll-up walls, etc., the light dep technique can help you get the most out of the grow calendar for your area by limiting the sun the outdoor and greenhouse plants get. Similar to indoor grows, growers do this to, in effect,  turn out the lights. With darkness coming earlier, the plants will start to flower when you want to instead of when the plant wants to. The light dep technique allows growers to utilize the natural sun while gaining the benefits of indoor grow harvest control. 

light dep technique for cannabis in a greenhouse
Light dep technique for cannabis in a hoop style greenhouse

What are the benefits of light deprivation? 

Using light deprivation techniques for cannabis can be great for speeding up outdoor cultivation and completing a harvest in a short season. It’s also good for avoiding cold and rainy weather in the later summer. This can be a lifesaver if bud rot is an issue for you.

If you’re growing in areas with a long growing season, you can use light deprivation to stagger harvests (e.g. multiple harvests in one season) or run one group of plants with light dep and another traditionally to get the best of both worlds. Light dep can get you from seed to harvest quickly when growing photoperiod cannabis cultivars. 

Another pro of cultivating with the light deprivation technique is that it allows you to utilize the sun’s energy, reducing your costs for lights and your carbon footprint. Getting the outdoor sun in a light dep scenario is also great for giving your plants everything they need without worrying about the tech inside. In outdoor grows or greenhouses, the light dep technique has been in agriculture for many years. Its application to growing cannabis is helpful and sure to stick around. 

Check out the Marijuana Grow Bible, if you want to learn more about growing this magnificent plant.

Are there any cons to light deprivation? 

As great as light dep weed is, there are some things to consider that aren’t so great. First and foremost, by controlling the timing of your plants’ flowering phase, you’re reducing time spent in the vegetative stage. This means you’re getting smaller plants overall with fewer flowers per plant than full traditional outdoor grows or greenhouses. 

During light dep, your plants need to be in the dark. That means tarps or covers should stay on and not be interfered with, as bright light exposure can affect the transition from veg to flowering. Covering plants in some regions will generate additional heat and humidity in the garden, which must also be dealt with.

For example, if you’re running light dep in a warm location, you might need fans or other cooling to keep the temperature down. The downside of running this cultivation method outside is that you must be there every morning to open the plants and every evening to close them again. Doing this twice a day can be very time-consuming or labor-intensive, depending on the size and style of your grow. In some situations, it can also result in tears appearing on the tarp, which can cause light leaks.

Automation can free up some time but comes with associated costs and maintenance. While not perfect, the light dep technique can be the right method for you or, at the very least, a good tool to be aware of if you need to harvest earlier or maximize your growing season.

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What type of seeds are best for light dep?

Start with photoperiod cultivar seeds when planning to grow outdoors with the light dep technique. Since autoflowers don’t rely on the light to flower but instead mature with age, they are not suitable for this. 

Photos will switch to flower when you change the light schedule to 12/12. In addition to that, some cultivars may grow better under light dep conditions. In particular, those that are vigorous and fast-growing, since you’ll be cutting down on veg time, are best.  You want your plants as big as possible before switching to flower.

Choose a cultivar right for your region and consumption preferences. As long as it’s not an autoflower, you can’t go wrong trying the light dep technique. 

Here are some great seeds to use while practicing light dep:

Indoor vs. outdoor weed: Which is better? Find out all the answers in our ultimate comparison guide.

Indoor vs outdoor vs light dep – what’s the difference? 

There’s a pretty solid line separating outdoor and indoor cannabis, as cultivators and consumers all have their preferences. The line is being enforced by recent studies that look at indoor vs. outdoor setups.

If done well and in good environments, indoor flower will have higher THC, but outdoor flower will have higher terpene content and less anxiety-inducing THCA. If we throw light dep into the mix, the line gets blurry. No current studies take light dep into account, but I’d hypothesize that most light dep flower would be similar to outdoor flower as the light being used is the same.

In some controlled greenhouses, using light dep may be more closely related to indoor conditions, especially those supplementing with lights. This difference is still being investigated further by the community but largely comes down to your preferences, grow setup, budget, and perspectives.

A fully automated greenhouse using light dep, like this one, might not be in a home grower's budget, but it's something to aspire to. Photo credit: HippieRunner1 from the ILGM forum
A fully automated greenhouse using light dep, like this one, might not be in a home grower’s budget, but it’s something to aspire to. Photo credit: HippieRunner1 from the ILGM forum

Can you use light dep without a greenhouse?

The light dep technique is often used with greenhouses as they house structures that can be used to support and attach tarps on the roof and walls. This is not needed to benefit from the technique, though. Any outdoor grow can be set up to run light dep, but it may take a little extra work. You can build frames around your outdoor plants to hang light-blocking material or try various other methods to block the sun. The goal is to get the plants in complete darkness consistently. Different grow setups may offer different solutions. Remember to monitor your humidity and heat levels as they can run higher due to light dep. 

light deprivation technique using a greenhouse
Light deprivation technique using a hoop house

Growing marijuana in a greenhouse is easy! Here our grow guide with tips and tricks for your next greenhouse grow.

How to setup light dep at home

In the cannabis industry, large greenhouses run automated light dep systems to run this process at scale, but it can also be done at home. The material for any setup can be the same. Start with black and white greenhouse plastic sold in big sheets or rolls. The material has UV-resistant white on one side and black on the other. Stretch it across your plants or attach it to frames that can be moved over plants outdoors

If you’re cultivating in the ground, you can build permanent frames to make the process easier. If you’re cultivating in pots, you could move them into a dark space instead of covering them. The solution for light dep will be slightly different based on your setup, but keep in mind that when you switch to flower, you’ll need to consistently keep the plants in complete darkness for 12 hours a day until harvest.

Make sure to set up a reliable and easy system to work with over time. For small grows, this can be as simple as a small wooden frame or plastic hoop house. If you’re looking for more detailed information on how to do this, I suggest reading our guide on setting up a light dep.

My free harvesting mini-guide has a handy cheat sheet, be sure to download it below!


The light dep technique isn’t revolutionary to agriculture but has started to gain traction in outdoor cannabis cultivation recently. It gives outdoor cultivators the ability to decide when to harvest rather than waiting on the seasons. This helps avoid inclement weather, potentially get more than one harvest out of the same season, and reduce energy costs by relying on the sun’s natural light. 

Using light dep is always a good option if your growing season is short or particularly humid and cold towards the end. While bringing many benefits to the table, there are some potential downsides to keep in mind with light dep like harvest size, humidity, and temperature and keeping your plants dark during the day. Light dep is used in all levels of cannabis cultivation but can be started simply and worked into regular home growing methods to have outdoor and greenhouse flower ready earlier in the season. 

Being able to harvest quicker means you can learn quicker, and there is always more to learn in the world of cannabis cultivation.

Keep on growing!

Avatar for Rob Sanchez

Mr Rob Sanchez

Cannabis Cultivation Expert

Rob started cultivating in 2011 and worked in Colorado's medical days as a cultivator and hash maker before getting involved ... See profile

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