When a plant outgrows its plant container, it is "pot-bound" or "root-bound." It no longer grows, and its roots begin to come up out of the dirt, as well as emerge from the drainage holes on the bottom of the plant container. The roots have become cramped and packed tightly into the container, like the roots of the bush lily in the picture on the right.
To prevent your container plants from becoming pot-bound, they need to be repotted every year or two. If you want to keep them in the same plant containers, you will still need to take them out and trim their roots before planting them again.
To Repot a Container Plant:
1. Choose a plant container that is several inches wider and deeper than the plant's current container, and put at least 2 inches of potting soil in it so the plant has room to grow.
2. Take the plant out of its old container. Sometimes it may be stuck because strong roots have come out of the drainage holes. Hold the plant container upside-down and try to slide the plant out. You may have to hit the bottom of the plant container or cut some of the roots that have grown out of the drainage holes. Sometimes moist potting soil makes it easier. It is easy to drop plants and damage plants that are stuck in their containers, so be very careful!
3. Trim the plant's roots and try to spread them out a little.
4. With the 2 inches of potting soil on the bottom of the new plant container, put the plant's root ball in the center of the container and put potting soil around it. Pack in the potting soil and water the plant thoroughly.
5. For the next several weeks, make sure the container plant isn't getting too much sun, water or fertilizer. Fertilizers at this point can give your plant root burn, and too much water can lead to root rot (for this, watch for browning leaves). The plant should recover completely within several weeks.