Place your potted magnolia tree in a location that has at least partial sunlight. That part is easy, but the biggest challenge in container-grown magnolia tree care is watering properly.
It is possible either to under-water or over-water magnolia (or any other tree, for that matter). While everyone knows that under-watering can be a problem, over-watering is less obvious but just as lethal. One cause of over-watering is the use of pots that do not have adequate drainage.
Water just sits in the bottom, resulting in root rot. Using pots that are too large for young magnolia trees can have the same effect. You end up watering a mass of soil that is too great for the poor little roots to absorb. The water retention of the soil will be excessive, causing the magnolia trees to have chronic “wet feet.”
No exact amount of water can be specified because conditions (temperature, humidity, etc.) vary so much. Your best bet is to judge by weight. That is, pick up the container; if it feels light, give your magnolia tree a thorough watering (as in watering until the water comes out through the bottom of the pot).