Magnolia is the most suitable time for basin changing is in April. When basin changing, you should choose a flowerpot larger than the original one, so that its root system can have sufficient space to grow.
When you plan to change the basin, you should water the four sides of the basin one day in advance, so that the soil can be better separated from the basin, or you can dig a circle of the soil on the edge of the basin, take the Magnolia and the original basin soil together, when you change the basin, you can cut off some old rotten roots, help it grow new roots, and promote the growth of new branches.
When you change the basin for magnolia, you should choose the permeable and loose soil, the best is sandy soil. You can apply a proper amount of base fertilizer in the basin soil. After you change the basin, you must water it thoroughly for the first time, and usually you can spray water on its leaves.