To properly look after a cactus, three main factors must be considered: heat, light and water. Cactus plants have evolved to thrive in poor environments, where soil has little to no nutrients. They require little space because they are slow growers and are commonly sought after for their low-maintenance qualities.
Use a sandy, free-draining soil. Purchase it or you can make your own by combining 2 parts compost and 1 part washed nursery sand. Clay pots are much more efficient for this type of plant than other types of pots; they help the soil dry out after watering.
Allow the soil to dry between waterings to prevent the roots from rotting. During the winter months, refrain from watering the cactus at all, as cacti and many other perennials take a rest during the cooler months. After the dormant period ends in spring, the growing season will begin again and you can resume the watering cycle.
Look for new growth or flower buds. Provide the plant with just a little bit of water at first, and gradually increase over the next few weeks. At the peak of the growing season, give the plant a good soak once a week, preferably on the same day each week. Ease off watering once again as autumn approaches.
Keep the cactus in temperatures no lower than 6 degrees. Although these plants are resilient, they have little to no tolerance for freezing temperatures. Plants kept indoors have little to worry about in terms of becoming too cold, but plants kept in a conservatory or greenhouse will require heat during colder months. Also, do not keep the plants in temperatures higher than 32 degrees.
Provide plenty of light. Cacti thrive in sunny places. In the northern hemisphere, place the plant near a south-facing window; in the southern hemisphere, place the plant near a north-facing window.
Feed the plant liquid 5-10-5 fertiliser at about one-third the normal strength once a month during the growing season. Avoid overfeeding the cactus, as it will encourage unhealthy growth.
Begin watering between two to four weeks before the spring equinox. During the peak of the growing season, cacti grown in a greenhouse will most likely dry out two to three days after they have been watered, requiring more frequent watering. Cacti kept indoors in a warm room will need light watering about once a month during the dormant season.