The coral cactus is not actually a cactus. It is a euphorbia that has experienced a mutation that causes it to become crested. The plant is native in Asia and is properly called Euphorbia lactea. The mutation is rare and is a sought-after trait by their Thai growers. The euphorbia is grafted onto a cactus stem to give it a sturdy base and an interesting look. This means it has the root system of a cactus and should be given cactus care which is similar to euphorbia care. Grow the crested euphorbia indoors or outside in U.S. Department of Agriculture planting zones 10 to 11.
Make a gritty planting mixture for the coral cactus. The plant is from arid zones and needs good drainage and plenty of grit. Fill a shallow dish with a half-and-half mix of potting soil and sand. Scoop out a depression big enough for the cactus.
Put on a pair of thick gloves to plant the euphorbia as the stem has spines. Plant the coral cactus just deep enough to cover the roots. Press the soil around the base of the euphorbia. Water the plant just to moisten the soil to the bottom of the pot.
Place the coral cactus in a sunny location where temperatures are at least 15.6 degrees Celsius. The coral cactus is an extremely slow-growing plant, but will preform best in warmer temperatures but at heats higher than 32.2 degrees C the cactus should be moved to a partially sunny location to protect it from burning.
Water the coral cactus when the bottom is dry. Stick a finger into the drainage hole to check for moisture. You can also slip a stick along the side of the pot and probe the bottom of the soil. Pull it out and if any soil is sticking to the stick the euphorbia is still wet enough.
Fertilise the coral cactus in spring, summer and fall once each. Make a dilution of fertiliser in the irrigation water according to the amount recommended by the manufacturer. The three feedings will give adequate nutrients to the plant during the growing season.
Euphorbia contains latex sap, which can be toxic to people with sensitivity. Wear gloves when handling the plant and don't get the sap on your skin or in your eyes or mucus membranes.