The pencil cactus is not a true cactus but a member of the Euphorbia family. It is originally from tropical parts of Africa and India. It can naturally grow into 30-foot tall tree with pencil-size green branches.
Pencil cactus is used in the Southwest as a landscaping plant and as a large houseplant in other parts of the United States.
The pencil cactus often turns red-orange as the weather cools, making it a very attractive ornamental plant.
Another name for the pencil cactus is milkbush. Like all members of the Euphorbia family, milkbush produces a white thick substance when the stem is cut. This sap contains the toxic component thought to be diterpene esters. It can be hazardous to humans. However, usually the amount you come in contact with will not kill you but will cause burning in the eyes and skin discomfort. A few people are highly allergic and end up in emergency rooms for treatment. It is recommended that pets and children steer clear of the plant.