The pencil cactus (Euphorbia tirucalli) is an interesting shrub with succulent foliage that’s native to semi-arid tropical climates. It can grow quite large in the wild. Mature plants feature thick brown branches with clusters of smaller green branches at their ends, which are cylindrical in shape and around the thickness of a pencil (hence the plant’s common name). On the branches are oval leaves that grow up to an inch long. Also, in the late spring and early summer, small flowers appear at the ends of the green branches. This plant lacks the sharp spines that are commonly found on many cacti.