Stunted growth, deformed limbs or leaves and a general decline are all clues that your plant may be pot-bound. When repotting, you should try to not disturb the roots because broken roots are very susceptible to rotting. Be sure the pot is dry before transplanting, and transplant into dry soil. Wait a week before watering to allow for the damaged roots to repair. If grown in a container, March is the best time for transplanting into a larger container, or as soon as new growth begins. After repotting, no water is needed until the soil becomes very dry. During the summer, water more often than in the winter. In the winter months, water just enough water should be given to prevent the shoots from shriveling. The solution to pot-bound plants is moving them into slightly larger pots.

      You can repot a tall, sharp-looking spiny cactus without suffering injury to yourself or the plant. Here are some tips to solving your prickly situation:

1). A good pair of gardening gloves will give you protection when transplanting a columnar plant, which can be held in one hand.
2). Use some newspaper to help prevent the thorns from sticking to your hands. Or cradle the cactus in strips of woolen blanket, sponge foam, or better yet, both.
3). Cover the hole of the container with a piece of window screen, rock or broken terra cotta.
4). Cover the bottom with a little cactus mix.
5). Loosen the pot-bound cactus with your hands and carefully roll the wrapped cactus to the side so that you can slowly release the plant from its original container.
6). Place the cactus in the pot and adjust it slightly so that it sits in the middle of the pot.
7). Add the cactus mix up to the soil line. Use a packaged soil mixture that's designed for growing cacti.
8). Tap the soil down with a small shovel.
9). For a neat appearance sprinkle decorative stones or sand around the cactus.

Important safety note: If you are transplanting any Euphorbia species, try not to allow the plant's milky sap to come in contact with your skin; the sap can severely inflame cuts or other sensitive areas. If affected, wash immediately with cold water and if necessary, seek medical attention.