Grow Tent Light Leakage – How Much Is Too Much?

Grow Tent Light Leaks - How much light leakage is too much for growing cannabis?

Grow tent and grow space light leaks can be a major problem. One foot candle of light is enough to throw your cannabis plants from the flowering phase back into the vegetative phase! That’s a major setback for cannabis growers.

One foot candle is defined as the amount of light that reaches a 1×1 foot area at a distance of 1 foot from a burning candle.

When to be conscious of grow tent light leaks:

Free Grow Guide to Download

You always want to be conscious of grow tent light leaks. Technically you can expose cannabis plants in the vegetative phase to light for 24 hours, but it’s not an ideal strategy.

In the cannabis flowering phase, it’s even more crucial to prevent light from reaching your plants during the 12 hour dark period every day. As you can see in the video, it doesn’t take much light to accidentally throw your cannabis plants back into the vegetative phase of growth.

Once cannabis plants accidentally “re-veg,” it’ll take weeks for them to be able to return to flowering.

How to prevent grow tent light leaks:

gorilla 2x4 grow tent

Not all grow tents are high quality, or maybe yours has a bit of wear and tear after several harvests. Here are a few good solutions to preventing light from leaking into your grow tent:

  1. Cover any holes on your tent in gorilla tape. This is the strongest tape around and should last a while without needing to be re-fixed.

      2.  Sew shut any holes or tears in your tent. It’ll take more time than taping but it’ll last longer if done properly.

          3. If possible, shut the lights and cover the windows in the room where you’re growing, so even if your grow tent has a bit of light leakage, the room outside the tent will be dark as well.

Prevent cannabis light exposure in an open space:

To prevent light exposure to your cannabis plants growing in an open space, consider Step 3 above. But you can also consider building a room partition around your plants, and covering the top of the partition with a dark sheet.

Consider using large pieces of cardboard, or even appropriately sized sheets of wood. You’ll want to make sure the structure is easily movable so you can reach your plants often to check on them and water them.

If you can’t make some sort of partition around your plants out of materials already available at home, a new partition may cost you the same or more than a grow tent. At that point, I recommend you consider a properly sized grow tent for your space.

Check out my other helpful articles like Using Molasses to Grow Cannabis, Free E-Books, or DIY Quantum Board Grow Lights.

How much grow tent light leakage is too much when growing cannabis?

One foot candle of light leakage is too much in a grow tent containing cannabis plants. Most modern smart phones can measure the amount of light present using an app.

How to solve light leakage in my grow tent?

Consider covering any light leaking holes with strong gorilla tape, or consider sewing them shut. Also consider making the room where your grow tent is located darker.


My name is Nick, and I'm a home grower who spends time writing about indoor growing tools and setups. My goal is for 420ExpertGuide to be a one stop shop for indoor growers to find the information they need.