After awhile potting soil breaks down and begins compacting in pots. This limits the amount of nutrients the roots can access in the soil, as well as inhibiting the process of taking in water. Fungal or other soil-borne diseases may also become a problem. Most fungal diseases live in the top layer of the soil, so the potting soil tangled up in the roots is not a concern. When you repot your plants in the spring, take the opportunity to replace the soil. The plant does best if the same type of soil is used that it has been growing in.
Grasp the plant around the stem near the soil surface with one hand. Pull the pot off the root and soil ball with the other. If the pot is stuck, thump it a few times to loosen in.
Inspect the root ball of the plant. If the roots are tightly packed together with little visible soil, it needs to be repotted into a pot 2 to 3 inches larger than its current pot. If not, it can be placed back in the same pot after changing the soil.
Crumble off the top 1 to 2 inches of soil on top the root ball with your fingers. This layer likely doesn't have roots in it and should crumble away easily.
Shake the roots gently to dislodge the excess soil around the roots. Avoid bending or breaking the roots.
Place 1 to 2 inches of fresh soil in the pot. Set the plant in the pot and add more soil underneath until the top of the root ball sits 1 inch beneath the rim of the pot.
Add soil around the sides and top of the plant until the plant is at the same depth it was at previously. Generally, the crown of the plant should sit at soil level. The crown is where the leaves emerge from the root system.
Water the plant until the excess moisture drains from the bottom after repotting. This collapses any air pockets in the potting soil, allowing the roots instant access to the water and the fresh nutrients in the soil.