How to Build a Marijuana Grow Box

Sophia Delphi May 11, 2022 - 7 min read
Fact Checked
A marijuana grow box with two bushes of weed in pots at home

You’ve finally decided it’s time.

You’ve been paying dealers for weed for years. Even though you’re now close enough to dispensaries to buy your bud legally, it still isn’t cheap.

It’s time to start growing your own supply.

But that may be easier said than done. What do you do if you don’t have private outdoor space for your plants, and your house or apartment isn’t large enough to set up a grow room?

A grow tent might work for some people, but that still means giving up a closet or part of a larger room. There’s an even better solution when you simply can’t find anywhere else to grow weed: marijuana grow box.

Here’s what you’ll need, and how to build your very own weed garden in very limited space.

What is a Marijuana Grow Box?

It’s essentially what the name implies.

A grow box is an enclosed container that holds everything you need to cultivate a small cannabis crop. It has built-in ventilation and lighting and usually has reflective material attached to the inside to maximize the effectiveness of the grow lights.

You can purchase pre-made grow boxes that will hold between one and ten plants, and they’ll come with all of the accessories you need to get started. Some have sophisticated ventilation systems that ensure no weed odor escapes; there are even some with smartphone apps that let you monitor your grow remotely.

You might also have to pay more than $1000 for one of these small, full-featured grow boxes. That’s an awful lot to invest when you’re just starting out, only growing a few plants, and not sure if your thumb is green or very dark brown.

The cost-conscious alternative is to build a marijuana grow box on your own. And it’s not that difficult to do, whether you’re an accomplished DIYer or only took a shop class in high school.

Let’s get started.

What Kind of Box Do You Need?

Here’s the encouraging news: it doesn’t really matter. Sure, it helps if the box is new and sturdy, but you can use almost any decent-sized empty container as marijuana grow box.

  • If you have an available standalone cabinet or wardrobe, that’s ideal.
  • A refrigerator that you’re no longer using can function as a grow box, as long as you’re able to remove some of the inside walls and shelving.
  • An old storage trunk can be turned on its end to function as a grow box.
  • You can even use a plain old cardboard box if its walls are thick enough to support attached fans and grow lights.

How big should the box be? Four feet high or taller is best for sativa plants, and they’ll still need to be pruned regularly. Indica strains grow smaller and bushier, making them a better choice for indoor grows in limited space. Even so, your grow box should be at least three feet tall.

The ideal width and depth will depend on the number of plants you expect to grow; figure at least two square feet per plant.

That’s the box. Now what?

Where to Put Your Marijuana Grow Box

Before you take out your tools, spend a few minutes making sure that you’ve chosen the right location for your grow.

Many first-timers immediately think about putting their plants in the attic or basement, but that’s probably a bad idea. The temperature surrounding your grow box can’t get too hot or cold, too humid or too dry; attics usually get hot and stuffy in the summer, and basements get chilly. Choose the wrong location and you’ll have wasted your time, effort, and money.

Areas that remain right around room temperature are where your plants will thrive, and there should be power outlets, easy access to running water, and an ample flow of fresh air. If discretion is also important in your personal life, consider that as well.

Get Stocked Up

The first step is to acquire the accessories you’ll need.

  • Two small exhaust fans mounted in frames; plastic is fine.
  • Grow lights; there are many choices, but fluorescent lights can be mounted close to the plants, don’t cost much to operate, and don’t generate much heat.
  • Reflective duct tape, glue, and either Mylar sheets or lots of tin foil.
  • Tools that you’ll need to cut the box; a boxcutter for cardboard, a saw for wood or metal.
  • Your plants, growing medium, and pots.
  • A surge protector is optional, but it’s a good way to protect your equipment.

Building a Marijuana Grow Box

It’s time to get this grow on the road.

One caution before starting: remember the adage “measure twice, cut once,” particularly if you’re using a cardboard container.

  1. If your box doesn’t already have a door or opening that will allow you to access your plants, create one.
  2. Measure your fans and cut holes in the box to accommodate them. One hole should be on the wall opposite the door, about 3-4 inches from the bottom. The other should be on a side wall, about 3-4 inches from the top.
  3. Place the fans in the holes and secure them with duct tape, if necessary. The bottom fan should be blowing in (to provide and circulate fresh air), the top one should be blowing out (to remove stale air).
  4. Cut another hole near the top of the box, large enough to accommodate a power cable for the fans and your lighting.
  5. Cover the interior of the box with Mylar or aluminum foil, glue it down, and don’t scrimp. A poor second choice is to paint the interior white. Make sure the fans aren’t covered.
  6. Hang your grow lights from the top of the box; many people use hooks. If you’re using standalone grow lights, position them where you want them to stand.
  7. Double-check to be sure there are no gaps around the fans or the power cord.

You’re done! You may want to add a few other touches, like a shallow tray on the floor to catch any dripping water (don’t forget, there’s electricity in the box), a timer for your grow lights, a carbon filter for your exhaust fan (to cover any odor), and a hygrometer (to measure humidity). If the humidity in the space is too high or too low, it could be a good idea to add a humidifier or dehumidifier as well.

One final warning: growing can be addictive. Don’t be surprised if want to upgrade to a grow tent or a complete grow room once you’ve harvested your first crop.

How to Build a Marijuana Grow Box: FAQ

Q: What strains are best to grow in a grow box?
A: You’ll probably want to stick with indicas because of their smaller plant size; autoflowering indicas will grow even smaller and flower more quickly. Miniature strains like Royal Dwarf and White Dwarf are good choices. If you want to grow a sativa, try Amnesia Haze which doesn’t grow as tall as most other sativa strains.

Q: Isn’t using fluorescent lights going to mean less productive grow?
A: It can, but there are some ways around it. Be sure the lights are hung close to the plants, and use additional lights if you’re growing more than one or two plants. You can certainly use HID or LED lights instead, but HID may be overkill in a small space and LEDs are quite expensive.