Cowboy Cactus Euphorbia acrurensis

Cowboy cactus takes its name from the outline it makes: tall, ridged columns standing straight up, with arms that rise from the main stem and turn skyward, much like the saguaro of a western film. It is not a cactus at all but a euphorbia, and the giveaways are the milky sap and the small paired spines set along each ridge, where a true cactus carries its spines in clusters from small felted pads. Young plants are mostly one or a few deep green stems with sharply angled ribs; branching comes with age, so the candelabra shape is something it grows into rather than something it arrives with.

That vertical habit is the reason to choose it. In a narrow bed against a wall, at the corner of a gravel garden, or as the upright among agaves and aloes, it gives height without taking width, and a group of three at staggered heights reads as one strong feature from across a yard. Larger plants carry a lot of weight high up, and that shapes how they are planted.

Planting a tall, heavy column

Give it full sun and ground that drains quickly, and set it at the depth it sat in its container, since burying the stem invites rot. A wet root ball gives way in the first strong wind, so stake a big column for its first season with soft ties, padded where they cross the ribs; in a pot, choose terracotta or concrete over plastic for the weight. Plant into dry or barely damp soil or mix and hold off watering for about a week, which lets any roots damaged in planting seal before they sit in moisture, then give one deep soak to settle it. After that, water deeply and rarely through the warm months and hardly at all from late autumn to spring.

In the humid parts of Queensland and New South Wales, summer rain is the test rather than drought. A column standing in soggy ground through a muggy February can rot from the root up; it shows first as a dark, water soaked patch low on one ridge, and that patch has to come out at once. It is frost tender as well, and a cold night leaves tan scars on the ridges that never fade, so plant it out only where frost does not reach. A plant raised in shelter can also sunburn if it goes straight into blazing exposure, so bring a new plant into full sun over a couple of weeks.

Choosing among the tree euphorbias

Where a bed is wide enough to take a broad crown, the Candelabrum Cactus is the alternative; in a bed under a metre deep, or for a row of verticals along a fence, cowboy cactus is the one that fits. For something low and flowering at its feet, Euphorbia milii brings red, pink or yellow bracts through the warm months on a small spined frame. Once the stake comes off, cowboy cactus needs no clipping and almost no water, which is why it belongs to the low maintenance range.

Cutting out damage safely

Pruning comes down to one job: taking out damaged or rotting growth with a clean saw or knife, back into firm, sound tissue. Before the first cut, put on gloves and eye protection, cover your arms and have a hose running, because the wound bleeds a caustic white latex that burns skin, can do lasting damage to the eyes and is toxic if chewed or swallowed, which matters with dogs and young children. The flow is heavy at first, then the wound dries to a scar. The spines tear sleeves and skin, so give it at least a metre of clear ground on any side people walk past. It rarely needs feeding, and pests seldom bother it.

Choosing a size

This plant is available in 2 sizes, from 300mm up to 500mm, priced from $309.00 to $2509.00 per plant. The size shown is the pot the plant arrives in, which is the rootball, not the height of the plant. Every size here is established stock rather than a starter plant, so this line is intended for immediate effect rather than for growing on. Not sure which to choose? Read our guide to low water gardens.