Prescription The most effective way to manage its height is to “top” the plant. This means cutting off the growing tip of your tallest stem. Use a sharp, clean knife or pruning saw, and wear thick gloves as euphorbia sap is highly irritating to skin and toxic if ingested. Once cut, the plant will often branch out lower down, creating a more compact, sculptural shape. You can also root the cutting: allow the end to callus for several days, then pot into dry, gritty compost.