Building a Grow Cabinet Part One: Lighting

by Alex Robles

Sometimes there are situation like prohibition or state regulations that make people have to take their cannabis gardens indoors. When that happens space is usually limited and stealth is a must. In these situation a grow cabinet is the perfect solution. The beauty of growing in one of these is that we can make it as big or as small as we need it to be. In the past I’ve used things that are already put together like a closet, locker or cupboard and other times I’ve had to build a custom cabinet. This series will go over the basic information that has to be considered before we put together a micro-grow or grow cabinet. I’ve tried to put this information into bite size pieces that can be easily understood but that have to be considered before we put together a small indoor grow space.

Once the size of the grow space is figured out I can move on to what I like to call “The Grow Cabinet Triangle”. The triangle is something I use to make sure most of the big questions that come up when growing in a confined space are covered. The three points are lighting, ventilation, and odor control. In the next series of articles I’ll go through each one of these points and give the best advice that I have, explained the best way I know how.

Lighting

It’s important for me to know how much light I’m going to need because too much light will cause light toxicity and too little light will cause yellowing and stunted growth. A quick general rule that I use to figure this out is “ 50 watts per square foot of grow space” for plants in vegetative growth, seedlings will need less and flowers will need more. It doesn’t have to be exact, a little under or over is OK. When I’m choosing a light, I don’t get caught up with lumens becaused I learned a better way to measure usable light is by using a PAR (photosynthetically active radiation) or McCree curve. Either one of those curves shows that plants absorb light best when it covers a range of 400nm to 700nm (nanometers), I like to use a full spectrum LED (light emitting diode) light that covers this range. The next thing I’m going to have to think about is how much heat that light puts out because I’m going to have to exhaust (remove) that somehow. This is another reason why I like to use LEDs for this type of setup, they will use less energy and put out a lot less heat when compared to HPS (high pressure sodium) or CFL (compact fluorescent light). Then I have to remember that all of those lights defuse (throw/spread out) the light differently, an HPS will defuse the light in a wider circle than a CFL and they will defuse wider than LED. This is important for me to understand because LEDs throw a narrower beam of light, so I’ll have to hang or mount them closer together to avoid dark spots in the grow.

The Cabinet

The first thing I’m going to do is paint the inside of the cabinet flat white from top to bottom. I do this because white reflects more light than mylar will. I paint the ceiling and the floor because I want to make sure that any light that isn’t hitting my plant directly is going to bounce off any surface in there and hit the plant indirectly. The paint fumes will linger for awhile so I’ll wait until I can’t smell any before I put any plants in the cabinet. This is important to remember because I can do a lot of damage to the plants by putting them in a confined space with paint fumes.

For a small space that is going to be used for seedlings, clones or sprouts a T5s will give me plenty of light without to much heat. For example, in a cabinet that measures 2’L x 2’W x 18”H I’ll put two single 2ft T5 lamps up. I like the singles because most of them can be daisy chained together and come with surface mounting clips so I can attach them to the ceiling diagonally, maximizing my space. Then I’ll make sure there’s a 6500K bulb in them to give me the cooler blue wavelength that young plants enjoy. That’s all the light I’ll use in a space that size.

In a larger space that’s going to be use to veg in I like to have more light and height. If you haven’t figured it out yet, I’m a fan of LED especially in small spaces. For a cabinet that measure 2’L x 2’W x 5’H I’m going to want about 200 watts of light with a good PAR or McCree range. The thing that I like to use is an LED grow bulb because it’s going to let me adjust the height of the light over different size plants. Since those grow bulb come in 12w, 24w, and 36w I can fill up that space with as much light as I need. The bulbs that I like to use cover a PAR range of 460nm, 630nm, and 660nm which is pretty good range for a bulb. Now I know there’s more innovative, cutting edge LED technology out there. And I respect what those companies are doing, but if you’re on a budget this type of LED grow bulb is something to think about.

Remember that when we grow indoors, that we’re trying to recreate nature and we will mess it up sometimes. Well I hope this helps you put together a grow cabinet. I think you should do it, it’s the winter time, what else are doing. Don’t be lazy, sharpen your pencil, put fresh batteries in the calculator, get the measuring tape out and do it. In the next part I’ll go into “ventilation”, I haven’t decided if I’m going to do “odor control” at the same time since they go hand in hand. I’ll post links to the lights that I use below. That’s it everyone, enjoy your day.