While repotting is generally thought of as a spring chore, it can also serve as a winter spruce up for outdoor plants -- allowing you to replant in more decorative pots for indoors or transfer from pots that have been damaged over the summer months. Remember that fall replanting will not have the stimulating effect that spring repotting does. Transplant young, fast-growing plants into larger containers so their roots can grow to take in moisture and nutrients to support the top growth (foliage). Repot older plants periodically so they don't languish in small, tightly packed pots that require frequent watering.
The longer a plant stays in the same pot, the more likely that the salts and mineral residues from water will build to harmful levels in the potting mix. And the mix itself, mostly organic elements such as peat moss, disintegrates. Repotting replaces the tired mix with some fresh mix, which often contains a starter dose of fertilizer. If it doesn't, wait two weeks, until new roots are less vulnerable to fertilizer burn, and add a balanced liquid food, following label directions.
How to Repot Houseplants
1. Cut away extraneous top growth. Turn the plant and pot upside down, and supporting the soil with your open hand, tap the bottom of the pot with your other hand, or tap the edge of the pot against a hard surface to gently ease the plant out of its container. Determine whether the plant is root bound (if the roots look too crowded or are growing in circles around the edges of the pot.) If the roots are shallow, repot the plant in a pot of the same size filled with fresh potting soil. If the plant is root bound, transplant it to a pot about 1 inch larger than the original. In both cases, the new pot should be sterilized.
2. Lift the plant with one hand, and gently tease the roots apart with the other, pulling the roots downward and away from the soil. Don't worry if some of the roots fall off.
3. Place a terra-cotta shard over the drainage hole at the bottom of the new pot, then fill it with some fresh potting soil containing a mix of topsoil, peat moss, perlite, vermiculite, grit, charcoal, slow-release fertilizer, and bonemeal. Add some water to moisten the soil.
4. Set the plant in the fresh soil, centering the top of the root mass 1/2 inch below the rim of the pot. Put new soil around the top of the plant, keeping soil at same level it was previously. Water the soil again.
5. Using a chopstick or a bamboo stick, tap on the surface of the soil to help work the soil around the edges of the plant so there are no air holes. Tamp the pot on a hard surface to pack the soil to remove air pockets around the roots and the wall of the pot.