I want to make an autonomous system that sustains light for indoor plants. For that purpose I want to isolate plant from outside light sources. In that way I can apply all kind of light cycles that I want.

I will use a LED system for light.

I thought a curtain would be suitable. But I couldn't decide what kind of curtain would be best.

Do you have any experience on that?

  • Will this be fairly permanent or do you intend to remove and reinstall frequently? Nov 26, 2016 at 13:32
  • 1
    I recently did a plant trial for my diploma, comparing the growth of plants under strobe lighting to constant light. We cut up black mulch plastic off a roll, and taped it in place. It works well if you have a box structure to tape the plastic to
    – Nic
    Nov 28, 2016 at 0:46
  • Did you have another group with light and dark periods? I am sure plants need down time, just how they evolved.
    – stormy
    Nov 28, 2016 at 7:44

3 Answers 3


The best curtain is made from those heavy contractor bags. Cut open and duct taped into what ever size you need. Make it at least a foot longer and a few feet wider for the space to block any cracks at the edges. If you are playing with putting plants into bud you have to have NO light entering the room. Treat it like a dark room for photography. During your 12/12 light/dark just don't go into the room at all during the dark or make a little entry where you enter, close the curtain then go into the nursery. Don't turn on any lights. Use red spectrum lights for budding and blue for the earlier vegetative growth. Duck tape is your friend. You MUST have big fans blowing where you SEE the plants moving otherwise you are going to get fungus problems. If you don't have Jorge Cervantes Encyclopedia of Cannabis go get that right away! It is all about one plant but this is the best 'garden' book I've found in a long time. Talks mostly about growing indoors. Big thick book full of pictures, graphs. Completely thorough and explained beautifully. Everything is taken down to the nitty gritty. Hope this is what you were hoping to read.

  • Absolutely critical to have full darkness if you are growing cannabis. My experience is that incomplete darkness can cause hermaphroditic behavior.
    – gorav
    Nov 26, 2016 at 20:34
  • Whoa, I've not heard that one, gorav. I do know that any light could set the time schedule back for harvest. Have run into finding ONE male flower on one of the females each crop that can pollinate every plant. Yet we are fastidious about the darkness/light. Do you use something different or do you even need to use black curtains? You should be able to enter the room with a green light? Do you have Cervantes' Encyclopedia? What do you think?
    – stormy
    Nov 26, 2016 at 20:59
  • Personally i've found a light issue every time I've had hermaphroditic behavior, though it certainly can happen without it. Haven't read Cervantes book, but will give it a look. I've been retired since I had kids, but am hopeful that I can return to my favorite pastime in the coming years.
    – gorav
    Nov 26, 2016 at 21:04
  • It is a perfect addition in our 'golden years'...not to be used when younger. Sigh. But that will happen once we have culture passed down to kids from parents. You will love this book. This is so detailed and researched and then explained for pretty much anyone to understand. Jorge is wonderful. He made his 'problem' into a great job. When someone reads his book they will have to see that a lifetime of pot doesn't make someone stupid (just when smoking). And stupid when after 60 is so very much fun! Who cares if it really helps with pain? Certainly just don't care if you've got pain.
    – stormy
    Nov 26, 2016 at 21:14
  • Do you have any other resources related to growing indoors? I couldn't find it in my library. And I think there are no electronic edition of this book. Nov 27, 2016 at 10:25

Typical approach is to simply choose a room (closet, in most houses, or a basement room) without windows. Walls are reliably opaque. A freestanding "closet" would be another approach. In plant resarch this is called a phytotron and typically includes control of temperature and humidity as well as light.


Another option is to buy a commercial indoor grow tent as these are specifically designed to let no light in when fully closed up (with zips).

Some things to note about tents like these:

  • They come in a plethora of different shapes and sizes

  • The interiors are lined with a reflective material (often silver in colour) to ensure that very little light from the grow light is wasted (in your case, LEDs).

  • Stitched properly at the seams to avoid even the smallest amount of light from entering during the dark period.

  • Include ventilation holes with appropriate pull strings to keep a tight fit around the ventilation fan or ducting.

  • Some tents include a viewing portal that can be used to monitor the plant without fully opening the tent (without affecting the climate inside, if this is something that needs to be kept stable)

  • I've been amazed at how inexpensive grow tents are. It's all the associated equipment that costs money....
    – Tim Nevins
    Mar 27, 2019 at 16:59
  • @TimNevins Yeah you're right. And honestly, I feel like it's the type of thing that you could probably even afford to skimp out on a little bit. They're not the type of product where branding often helps guide buyers to a better reputation for quality. I've seen a few top brands (I won't name who) really overpricing their tents.
    – dope
    Mar 28, 2019 at 2:25

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