The key to understanding where cacti survive is noting that they are adapted to regions where the environment is limiting and that there is a lack of competition from other vegetation in terms of light, moisture and nutrients. Depending on their habitat, cacti have a variety of survival mechanisms to overcome their harsh environment. In the drier regions, cacti go dormant during the hot dry season and only grow and flower when there is moisture. Sometimes, the desert cacti flower, set seed and then go dormant again over the space of only a few days. In their mountainous and northern range, cacti go dormant during the cold season surviving temperatures of -30°C and below and only grow during the warm summer months. In humid jungles, cacti are epiphytic and grow in trees and have adapted to growing in shaded, nutrient poor environments by having flat stem segments to capture the filtered light efficiently and by having roots that absorb moisture and nutrients from water dripping off the trees that they're living on. In the home, the key to growing cacti successfully is to mimic some of these environments. For example, when your cactus is going dormant usually as response to daylength, restrict watering to only once per month and only increase to weekly to biweekly watering when it is showing signs of growth.

There is a commonly held belief that cactus plants are tougher and more resistant to neglect than other types of plants. The reputation of cactus plants for toughness is most likely due to two factors: their spiny, well- protected exterior tends to give them the appearance of being able to look after themselves, and they are also slower than most plants to show symptoms of distress. While most plants will yellow, drop leaves and wither soon after experiencing stress, a cactus will often simply suffer in silence until it suddenly drops over beyond hope of recovery.

The first step in ensuring success in growing a healthy cactus plant is to purchase one that is already in good health. Avoid any plant that has damaged spines, obvious signs of bruising, or that has lopsided or uneven growth. A plant that has put on new spindly growth during its time in the store should be avoided. Even under ideal growing conditions, the spindly growth produced in a dimly-lit store will never broaden out to normal size, leaving the plant with a permanent disfigurement. Ideally a cactus should be purchased in the greenhouse where it was grown, or as soon as possible after it has been shipped to a retail outlet.

The care required by a particular type of cactus is largely dictated by the climatic conditions where that cactus would be found growing in nature. A good rule of thumb for looking after any plant is to provide conditions as close as possible to those under which the plant would be found growing naturally. In general, the two most common classes of cactus are those of sun-loving and shade-loving.