How to Take Care of a Euphorbia Cactus

Pot your euphorbia in a clay pot in cactus soil or a well-draining potting soil mixed in equal parts with coarse sand. Place a 1- to 2-inch layer of pebbles in the bottom of the pot for a large euphorbia, to stabilize the pot. Place small pebbles on the top of the pot for decoration and to hold the plant in place if desired.

Water your euphorbia thoroughly after potting, but only sparingly afterward. Allow the soil to dry completely between waterings. Water the plant once every two weeks during the growing season and once a month during the winter, if they are kept indoors. Do not let the plants sit in water.

Place your euphorbia in bright, indirect light where they are protected from hot afternoon sun. Euphorbias do not like full sun.

Fertilize your euphorbia twice a year with an all-purpose liquid fertilizer, or use a slow-release fertilizer every six months. Do not fertilize the plant during the winter.

Protect your euphorbia from temperatures below 50 degrees by bringing them indoors or into a warm basement or garage. Watch for mealybugs while it is inside, and kill them with a cotton swab dipped in rubbing alcohol.

Watch for signs of rot, which include mushy stems and soft black or brown spots. Cut away all affected parts and remove the plant from its pot. Wash away all potting soil and cut off any dead or diseased roots. Sprinkle the roots and any cut surfaces with sulfur or fungicide powder and allow to dry for at least a week in a sheltered, shaded location. Repot the euphorbia in new, sterile soil and take care not to overwater in the future.