3. Water infrequently. Established cacti have less vigorous watering requirements than most other potted plants. Though they do require some water, their reputation as hardy desert survivors is well-earned. Most varieties of desert cactus require little water once they're fully established. Though individual species of cactus may differ in the amount of water they require, a good general rule is to let the soil dry out completely before watering. Depending on the temperature, this mean waiting a month or longer between waterings