A cactus is one of the easiest types of houseplants to grow and is readily adaptable to almost any type of environment that is comfortable to humans. If window space or sunlight is limited, you may want to try growing your cactus under artificial lights. Most varieties of commonly grown cacti and succulents can easily be grown in the home under artificial lighting.
Most cactuses require bright light. The general rule of thumb is to use 15 watts of light per square foot of growing space. For fluorescent lights, place them so they remain about 12 to 15 inches above the tops of the plants and adjust them as the plants grow. If you are using high pressure sodium or metal halide lights, keep the lamps a bit higher than that depending on the wattage of the lamp. High-wattage lamps need to be farther away from the plants to prevent burning from the radiating heat.
Like all types of plants, a cactus requires light in both the blue and red spectrum to properly grow. A combination of cool white fluorescent tubes and incandescent bulbs can achieve this, but it is more efficient to use specialty daylight or plant grow tubes without incandescent lights. Many metal halide lamp manufacturers produce full spectrum lamps that are suitable for growing cacti.
Cactus come from the equatorial regions where the daylength is usually about 12 to 14 hours of light with 12 to 10 hours of dark. A simple household lamp timer can be very beneficial in keeping a regular day to night light cycle and helps keep growth even and symmetrical. For cacti that are being grown for flowers, many species require short days to initiate flower buds. The day length required varies with the species being grown.
When selecting a pot for indoor growing, use containers with good drainage holes. Unglazed clay pots work very well because they help the soil dry out faster and the added weight keeps top heavy plants from tipping over easily. Shallow pots are preferred over deep pots because most cacti have a very shallow root structure that does not penetrate deep into the soil.
Cacti like a well draining soil that does not retain too much moisture. Equal parts sand and commercial potting mix works well. There are also many types of manufactured specialty potting mixes for cacti that will be sufficient.
Cacti are primarily desert plants that can tolerate long periods of drought. This does not mean that they should not be regularly watered. Be careful not to over-water, though, because this will cause root rot. A good way to tell if your cactus needs water is to poke your finger an inch or so into the soil; if it is dry, then water the plant. When watering, pour about the amount of water equal to the volume of the pot and let it all drain out the bottom. This mimics desert thunderstorm conditions.