Since you’re going to be growing indoors, using the correct cannabis grow lights will have a big impact on the outcome of your grow.
For the first stage of the growth process (the vegetative stage), High Output (HO) T5 fluorescent bulbs are the ideal light source. Plants in this stage of growth prefer longer wavelengths from the blue end of the light spectrum, and these T5 bulbs emit mostly that type of light. You can also use general purpose fluorescent lighting as an acceptable (and cheaper) substitute, but your plants will lose some of the faster-growing benefits that the T5s offer.
Fluorescent lights are generally cooler and cheaper to operate than any kind of incandescent lights. In an enclosed grow closet, this can be a big factor in keeping heat levels reduced. Since fluorescent lights also use less electricity, they’re cheaper to operate and don’t have as big an impact on your monthly electric bill.
To increase production and speed up the vegetative growth process, many growers leave their fluorescent lighting on around the clock. 24 hours of light each “day” keeps the plants in constant growth mode and has no negative effect upon them. It’s also recommended that you keep a 3 – 5″ space between the tops of your plants and fluorescent lights. Plant tops too close to the bulbs can get burned, and lights that are too far away from the plants have a tendency to make the plants stretch out.
Your plants will appreciate getting as much light as they can, particularly the lower leaves that are usually shaded too much by the leaves above. Plan on surrounding your plants with a bright surface (such as poster board or white paint) or a reflective material (mylar sheeting works best, but aluminum foil works pretty well, too) to capture and redirect any stray rays back onto your plants.
For the second stage of the growth process (the flowering stage), high pressure sodium (HPS) lights with Gro bulbs work best. (Some growers use MH, or metal halide, bulbs instead for different light characteristics. During the flowering stage, your plants shift gears and slow their rate of vertical growth, instead now concentrating their growing energy on bud (flower) production. Bud production is stimulated best by shorter wavelengths from the red light end of the spectrum, and HPS lighting systems provide these shorter rays.
HPS systems also tend to run hotter, so now keeping at least an 8″ distance between the light and tops of your plants becomes very important.
(You can use fluorescent lighting during the flowering process instead of a separate HPS system as a way to save money, but it will not work as well and you may very well find your crop’s output and potency lower as a result.)
Now that you’ve determined how you’re going to address the lighting requirements, it’s probably time to take a look at cannabis fertilizer and nutrients.