Cacti make beautiful houseplants that add character to any home. But perhaps the best part about cacti is that they are virtually impossible to kill. With a bit of soil, sunlight and minimal water they will happily grow and flower for years, which makes them a great plant for beginning gardeners and even those with notoriously brown thumbs.
Change your cactus’ soil. Unless you know when the cactus you purchased was potted, its a good idea to re-pot it as soon as you buy it. A cactus that is potted in quality soil does not need any fertilizer at all. Quality cactus soil should be composed of one part potting mix, one part washed sand, and one part coarse gravel. If your cactus does not grow or flower for a long while, it is a sign that its soil needs to be changed once again.
Water your cactus. House cacti need very little water–as little as one watering per month. To tell if your cactus needs water, insert a pencil all the way to the bottom of the soil. If moist soil clings to it, it is not yet time to water. Cactus soil should be allowed to completely dry out before it is watered again. Tap water is not good for cacti. If possible, use collected rainwater to water your cactus. Rain water causes chemical reactions in the soil that will provide most of the nutrients that it needs to thrive in its pot. If rain water is not available, use distilled water or tap water that has white vinegar added to it (one capful of white vinegar per five gallons of tap water). Never water your cacti with cold water. Bottom water your cactus by letting it sit in a saucer full of water, and do not let any water get on its flesh or roots. Cacti grow for only a few months out of the year, and when they are resting they need virtually no water. Different cacti have different growing seasons although most grow in the spring and fall and rest in the winter and summer. It is important not to over-water your cactus when it is resting. Research your particular variety of cacti to get to know its growing and resting cycles.
Place your cactus near a brightly lit window where it will receive sunlight for most of the day. However, if your cactus develops yellow or brown spots, it is a sign that is receiving too much light. To remedy the problem, simply move it to a spot that receives less light. If it turns a lighter green, it needs more light. Use its colors to help you find a balance.