The best time to re-pot your plants is in the spring. During the winter, your plants are not in active growth, so re-potting is not necessary. During the spring and summer the sun is stronger, days are longer, and plants are actively growing. This means they will be able to handle the stress better.
How will you know that it is time to re-pot a houseplant? If your plant has grown so that it has overwhelmed the container, roots are emerging from the drainage hole and/or lying exposed on the surface, and new growth and blooms are minimal then it is time to move your plant to a larger container. Another way to tell is to pop the plant out of its container. You can do this by placing one hand around the base of the plant, tipping it upside down, and tapping the side of the pot with your other hand. If you see one big mass tangle of roots, your plant is becoming root-bound and needs a bigger home. If you notice black, weak roots and/or an unpleasant odour the plant is experiencing root rot. If this is the case, the current pot probably does not have adequate drainage or you have poor soil conditions, and it is time to re-pot. In this case, do not increase the pot size.
Even if your plants aren’t showing any of these obvious signs for re-potting, it is a good idea to do it every few years anyway. The reason to periodically re-pot is because the soil will eventually lose its texture and will become overloaded with deposits from water and fertilizer. Be sure to use the same pot size until the roots need more room.
When you are choosing a container, get one 1-2″ larger than the current pot. Make sure that it has a drainage hole. Holes are necessary to avoid root-rot caused by excessive moisture. Make sure to choose a quality potting soil, never topsoil. Potting soil will stay light and airy, allow for good drainage, and allow oxygen to reach the roots. Topsoil would become a hard, heavy lump over time. Now that you have your pot and soil, it is finally time to get your hands dirty. Remove the plant from its container as per the directions above. Loosen the root ball so that the roots can find the new soil. Remove any weak or discoloured roots at this time. Place enough soil at the bottom of you container so that your plant will be at the same planting depth as before. Sit your plant in this bottom layer of soil. Next add potting soil around the edge of the plant and press in firmly until the container is full. Shake the container gently to ensure soil will reach any empty pockets around the roots. If your plant requires support like a trellis or a stake, add it at this time. Now simply water your plant thoroughly and decide where you would like to put it.