Your best bet is getting one of the new CO2-creating bucket kits such as CO2 Boost and replacing it after each harvest. This is a simple way to add gas without adding heat or hassles.
Some growers even go so far as to mount a large fan at floor level and an exhaust fan in the ceiling, creating a breeze from the bottom to the top of the closet that keeps air moving straight to the filters. This complicates things, but it’s probably the best way to keep aromas from escaping.
Unless you’re working in a walk-in closet larger than 4 by 4 feet, a 1,000-watt high-intensity discharge (HID) light such as metal halide (MH) or high-pressure sodium (HPS) is going to be too much light and heat for your space. Instead, light up your flowering chamber with a 400- or 600-watt HPS at the most (for a 4′ x 4′ closet) and a 150- or 250-watt HPS for a smaller space (2′ x 2′).
Fluorescents and LEDs will also work to grow out buds, but you can’t beat the light penetration and spectrum optimization you get from HIDs. It’s better to use fluoros and LEDs in your vegetative space and save on power usage and heat in that chamber, instead of skimping in the flowering area and winding up with wispier buds.
You must also anticipate the stretch that occurs after flowering is induced. Some plants will grow another foot or two in the fortnight between when you change the light cycle to 12 hours on/12 hours off per day and when you start seeing the telltale female “puffball” flowers forming. Raise the lights as the plants grow and leave enough space to continue raising them as needed.
Keep in mind that getting a gram per watt is a really impressive yield, so you won’t be producing pounds with every grow cycle. You should be able to get around 200 grams, or about 7 ounces, every two months or so, allowing you to smoke almost an ounce of bud per week without running out. On top of that, you’ll be producing your pot for pennies on the dollar—plus you’ll know everything that went into the finished product, from nutrients and pesticides to the loving care you spent daily to help your plants thrive. For medical patients and cannabis connoisseurs alike, nothing beats the feeling of creating your own stash year-round.
You’ll need to choose between a hydroponic, aeroponic, soil- or soilless-mix system for feeding and watering the roots of your plants. Soil (or more likely a soilless mix such as spaghnum peat or coco coir mixed with perlite) is always more forgiving and typically easier for the beginner grower.
More technically minded growers might want to experiment with deep-water culture (DWC) or ebb-and-flow hydroponic trays. The toughest way to grow—aeroponics—involves misting exposed roots with nutrient solution; when properly dialed in, aeroponics can grow bigger plants more quickly than any other method. Neutral substrates like rockwool and clay pellets provide a structure for the roots to grip, as well as a surface for moisture and air to collect in both hydro and aeroponic systems.
Whichever way you go, seal up the bottom 6 inches or more of your closet all the way around to avoid having any leaks seeping into your floor (or, even worse, to the floor below yours). This can be easily accomplished with some thick plastic and a staple gun. Rubber mats or splash tubs will also protect floors designed to hold little else than shoe racks and are easily removed and cleaned between harvests.
Potted plants will outgrow their containers every two to four weeks, meaning a transition that will shock them no matter how delicate you are. Always allow a little time for your babies to adjust to their new home before cranking up the light and nutes. Remember, the bigger the pot, the bigger the plant, because the size of the root system will directly determine how much food and water can be taken up. Fewer plants grown in larger buckets and provided with a longer vegetative time will outyield a larger amount of smaller plants that were induced to flower shortly after rooting.
Growers can maximize yield by using the “screen of green” (ScrOG), a derivative of the “sea of green” (SOG) method, in which branches are spaced through a wire or string grid to efficiently receive as much light as possible. Much like the art of bonsai, young twigs are trained to fill a desired space as they grow. By the time the plant is ready to flower, an even canopy will extend across your closet’s entire width.