Native to arid South Africa and India, pencil cactus is actually a euphorbia, thus making it a succulent and not a true cactus despite the name. There are thousands of euphorbias, and like all of them, the pencil cactus has milky white latex sap that is released when the plant is injured. This sap can be strongly irritating to some and hard to remove even with soap. If there is eye contact, blindness can occur, and ingestion of the sap can be fatal Outdoors, grow pencil cactus in full sun. Indoors, place it on a sunny, warm windowsill that receives a southern or western exposure. It also is happy living in a greenhouse. Provide immaculate drainage for pencil cactus. Bagged cactus soil is encouraged. Water every two weeks and less in the winter, and as with most succulents, it?s better to let pencil cacti dry out than to drown it or risk rotted roots. Fertilizing is not urgent, but if you want, try a balanced liquid houseplant food, feed pencil cactus once a year in the spring. Be cautious when pruning any dead stems to avoid skin contact with the sap.