If you’d like to start growing cannabis, but only have a limited space to do it in, then you may wish to consider a closet grow!
Tried and tested by teenagers the world over – including myself over 20 years ago! – growing in a closet is an effective way to get herb in your otherwise herbless life, and as long as you keep a few specific pointers in mind, it may well be the easiest way to grow cannabis indoors.
So, first of all, what do we mean when we say “closet grow”?
Well, quite simply, it’s a small space in a cupboard, wardrobe or closet, which is repurposed and kitted out with the necessary accoutrements to grow cannabis.
Keep in mind, closets – despite their perks – are not a plant’s ideal environment to thrive. So, the initial process of setting up a closet grow does involve some important factors. You have to think about things like ventilation, smell, light, and temperature…
However, if the closet is your only option – the end results could be well worth it.
Here’s the essential equipment list for getting started with your closet cannabis grow setup:
- Cupboard, closet or similar empty space
- Grow light, plus hangers/fixtures
- A timer to control your lights
- Container/s for your plants
- A tray for your containers to sit in, to minimize leaks
- A method of delivering nutrients
- A substrate such as soil, coco or rockwool (unless using a no-substrate hydro method)
- Water
- Effective airflow
- A carbon filter or alternative means of killing odor
- Some cannabis seeds or clones!
That’s the essential list – but you may also wish to consider the following items too, as they will make your life easier and will probably help you achieve better results:
- A hygrothermometer to check temps and humidity
- A pH pen or reagent test kit to determine pH of your water supply
- White paint or strong, heat-resistant plastic to coat the inner wall of your closet and increase reflectivity
- Canes or a net to help train and space out your branches
So what next? Let’s guide you through the basic steps ….
- Clear and clean the closet space thoroughly, ensuring that dust, dirt and any traces of mold are removed
- Paint the inner walls with white paint or cover with strong white plastic
- Hang your lighting setup
- Put your containers in place
- Set up and test your vent fans and carbon filter
- Start growing!
But that’s all very simplistic, and obviously things are going to come up along the way.
In order for you to avoid the major pitfalls associated with closet growing, here are some tips to keep in mind:
Choice of Light
In a tiny space, you’re unlikely to need a 1000W HPS.
It’ll be way too much light, and perhaps more relevant, it’ll be wayyyy too much heat. Better to stick with a 400W HPS, or even better, to choose a cool light such as a CFL or LED.
LED would always be my first choice, and even though they are still expensive to purchase a decent brand, you can build your own high-quality LED grow light for far less money, if you have a somewhat technical mindset.
With a programmable LED, you can even control your spectrum and intensity to make sure your plants get exactly what they need throughout the grow cycle.
Choice of Medium & Nutrient Delivery
You have the same choices here as any indoor grower, but some choices may be preferable due to your limited space.
For example, it may be difficult to move your containers around or reach them with a watering can every time you need to feed, so setting up a small hydro system with fixed irrigation lines in place may be preferable.
A four-pot Autopot system or similar with a 5-10 gallon tank would be ideal for a small closet grow.
If you’re growing in a bedroom, you may wish to avoid scattering soil around, so you may choose a less-messy medium for this reason. Coco coir, perlite, clay pebbles, or rockwool are common and comparatively mess-free choices.
Of course, your choice of nutrients will depend on your choice of water delivery and nutrients.
If you’re using coco coir as a substrate, you should use nutrients specifically formulated for coco, for example.
Also, if you wish to grow using organic nutrients, it’s harder (although not impossible) to use them in most hydro systems.
If funds are tight, you could also build your own simple ebb and flow (flood and drain) system for very little money.
Also, if you need more pointers on how to grow cannabis indoors hydroponically compared to growing in soil, take a look at this recent article.
Airflow and Aroma
Good airflow is crucial in any grow, but arguably even more so in a tiny space, where the total amount of air available to your plants gets used up very quickly.
There are several ways to handle airflow. Keep in mind that you need to keep your closet well-sealed to prevent odors leaking out (a great way to alert your parent or neighbors to the fact that you’re growing)!
You need to control the airflow in and out of your closet, and filter out the smells that will come out with the air. For some, this may be the trickiest part of setting up their closet cannabis grow.
A small vent fan, no bigger than 4 inches in diameter, will be more than sufficient to control the air in and out of your closet.
Set it up outside the closet and feed a short length of vent ducting into the closet. You may need to replace the door of your closet, or if it’s an option, you could cut through the door with a circular saw!
As well as a route out for your air, you need a route in.
One or two smaller holes of between 2-3 inches diameter should be sufficient to ensure air can get in. Try to make sure that your air comes in at the other side of the closet to where it goes out; this will ensure reasonably good circulation.
You can also add one or two small circular fans (even a clip-on desk fan or similar would help, if space is really tight) to move the air around inside your closet as much as possible.
Plant Height
If you’re growing closet weed, space is a problem in all directions. Often, you may have less than six feet of vertical space (including the space to hang your light), so you have to maintain maximum plant height carefully to avoid too much stretching.
This is especially true when using hot lights – I can personally attest to how badly plants can get burnt if they are forced too close to the light in a small space. Even when using LEDs, it’s important to maintain distance between the canopy and the light to prevent “light bleaching“.
So, in order to ensure your plants stay small, you should pick strains that will remain short-statured throughout their life cycle, start flowering as early as possible, and/or agressively prune and train your plants to keep them under control.
How tall do cannabis plants grow?
It depends greatly on its biotype – for example, autoflowering plants are a great option, as most of them top out well below a meter in height.
“Indica”-dominant photoperiod-dependent strains are generally more controllable than “sativa”-dominant strains, although this is a generalization; if you switch an indica-dominant plant to flower after just a week or so of vegetative growth, you can limit its stretch in early flower and keep it small.
If you are brave enough to try a sativa-dominant strain in a closet, it may be wise to skip the vegetative period entirely and give your plants a 12:12 light cycle from day one. They can often stretch so much in early flower that you’ll still end up with monsters under a constant 12:12 cycle, particularly if your plants are of tropical or equatorial origins, where light cycles are naturally around 12:12 all year round.
In any case, now is the time to put your pruning and training skills to the test!
You can carefully top and train your plants so that when they flower, they will utilize the available space as well as possible, and provide you the optimum amount of high-quality buds.
You may wish to use a technique such as manifolding, where the plants are regularly topped to create an even, candelabra-shaped canopy.
Interestingly, if you touch and move your plants a lot, the movement itself may actually reduce stretch. Even more reason to regularly – and enthusiastically – handle your plants!
Controlling Stretch
You can also control stretch by manipulating the levels of phosphorus available to the plant.
When levels are reduced, shoot growth is reduced in turn. It’s a technique that should be used with care, as phosphorus is an essential macronutrient responsible for various aspects of keeping your plants healthy.
However, if you carefully inhibit phosphorus in early flower, you can achieve a reduction in stretch with little to no adverse consequences – and in fact, a slight phosphorus deficiency at this time often makes plants appear greener and healthier!
Yet another way to control stretch is to carefully maintain your daytime and nighttime temperature in early flower.
If nighttime temperature is the same as daytime temperature, stretch is reduced.
If you can achieve lower temperatures during the early morning than during the night (a phenomenon that occurs in nature, due to the way the earth gradually releases infrared energy absorbed during the day), you can reduce stretch even more!
Later in flower (when your plants have truly stopped stretching), you should avoid creating a morning temperature dip, as you actually SHOULD create a positive day/night temperature difference (although not more than a 10°C/18°F difference, or you could cause excessive humidity and mold) in order to maximize cannabinoid and terpene production.
Light Spectrum
One final point about stretching, if you want to get technical – the ratio of red to far-red light influences the amount that your plants will stretch (i.e. the distance between the internodes).
If red light is much higher than far-red, your plants will have shorter internodes. If the amount of far-red light increases, the internodes will grow longer, and you’ll end up with tall, spindly plants and weak stems.
It’s important to note that the amount of far-red light available to your plants doesn’t simply depend on how much far-red light your lamp produces (although different lights give very different ratios).
It also depends on how easy it is for light to penetrate the canopy. Plant leaves absorb and block red light, but allow far-red light to pass right through.
So if your plants are densely packed, with crowded leaves and little space between them, the lower parts of the plants will receive a relatively much higher level of far-red light (as much as 20 times more!) compared to red than the top layer of the canopy, because the top leaves block most of the red light.
This triggers the shade avoidance response and forces your plants to stretch.
Of course, it’s not as simple as that, and scientists are still not sure exactly how far-red and red light interact, or exactly how that fits together with blue light.
But it’s clear that fine-tuning the ratios of all three (along with UV light) can have some very significant effects on plant growth.
If you want to have real control over your light spectrum, a programmable LED light is truly the way forward.
Some newer models emit far-red and UV light, and can be precisely controlled to emit the exact percentages of each type of light.
You can also change the ratio during the flower period – so in early stages of flower, you can fine-tune your spectrum to minimize stretch.
Then in late flower, you can manipulate it to increase resin and terpene production, and even to maximize production of the anthocyanin pigments that turn cannabis plants purple!
