Pencil cactus (Euphorbia tirucalli) an add spiky drama in an outdoor garden bed with other succulents and warm-climate plants. As a houseplant, it needs gritty soil and impeccable drainage.
Gritty cactus mix
Pencil Cactus: A Field Guide
With its spiky silhouette, a pencil cactusseems an obvious choice to add to a houseplant collection or garden bed devoted to succulents. And yet some people hesitate. Is it because Euphorbia tirucalli is not really a cactus? And is mildly poisonous? Let’s put those details aside for the moment and admire the sculptural beauty of a pencil cactus.
A succulent (rather than a true cactus), pencil cactus like thousands of other euphorbias varieties emits a milky white sap if injured; wear gloves to avoid exposure, which can irritate the skin.
Unless you live in a warm climate (USDA growing zones 10 or 11), your pencil cactus probably will live in a pot indoors (where it can reach a height of about 6 feet at maturity). Grown outdoors, E. tirucalli can get much bigger and reach a statuesque height of 30 feet.