According to the SFGate, to replant a bird of paradise, first heavily wet the soil. After inspecting the soil, inspect and cut the root mass as needed, move it into the new location and fill with potting soil around the roots. Many potted bird of paradise flowers are purposefully kept in a container that restricts their root growth, which can complicate the process of moving the plant.
Even if a bird of paradise plant seems large for its container, it is not necessarily bad, as these plants can thrive in such conditions. However, if the plant appears unable to get enough water, its roots are growing out of the top of the soil or coming out of holes in the pot, replanting is needed. Watering the soil should make the plant easy to remove from any current container.
If it is still too difficult to pull out, water it again and go around the inside of the container with a knife. Once the plant is out, inspect the roots for any discolored sections or an extremely rounded, tightly-woven root system. If discolorations are present, cut them off. If the roots are too tight, cut about 1 inch into the root mass in several locations. Replant in the ground or in a pot only 1 to 2 inches larger than the previous container.