Soil: The soil must be slightly gritty and well draining.
Sun and Temperature: Full sun and temperatures of at least 65 F. (18 C.) or warmer are necessary when learning how to care for a pencil cactus.
Water: It will need water approximately every two to three weeks in summer but no water in winter. Allow the plant to dry out between irrigations.
Care must be taken when caring for a pencil cactus to avoid the sap. Even eye protection is necessary because the pencil cactus plant produces a toxin that can cause an anaphylactic reaction. In most cases it can be cleared up with antihistamine but occasionally more severe reactions occur and are difficult to clear.