Watering has been the downfall of many budding collectors who, not knowing the correct watering techniques, have either over-watered and lost them by rotting or starved the plants of water so they have died of thirst. It is true that in their native state they only receive scant amounts of rain, but they also acquire water through their spines from the frequent heavy dews at night. In cultivation, cacti do enjoy a fair amount of water during the growing season. Begin watering mature cacti in early spring by spraying them overhead to gradually start them into growth. Then gradually increase to soaking the soil once new growth of spines appear at the apex of the plants. This indicates that it is in active growth. Then keep the plants just moist all the time.

If you live in an area which has summer rain, like most of South Africa, eastern Australia, and New Zealand, then watering plantings in rock gardens will hardly be necessary. In the dry summer areas, watering will be more frequent. Plants grown in containers, will require more attention. A clay pot will dry out more rapidly than an equivalent size plastic one, and therefore will need more water. As summer changes to autumn, the quantity of water should gradually be reduced until by the end of autumn, it is withheld altogether this is round about Easter time.

In winter the plants should be kept as dry as possible since any winter growth could greatly reduce the flowering possibilities of
the following spring the exception being any winter flowering cacti e.g. Mammillaria hahniana, woodii, brauneana. Seedlings must be watered for their first 12 months of growing. Mature cacti do not like stagnant water around them since this will encourage rotting. Cacti are more capable of withstanding the cold if they have been able to harden themselves during the growing with the gradual reduction of water. During the growing season, the plants can be watered freely any time of the day.