Magnolia trees are most popular in the South, but in fact, some varieties, such as the star magnolia, can also grow in the North--all the way to USDA plant hardiness zone 4. Magnolias are best grown in the sun and they prefer soil that drains well. Whatever climate you live in, you will need to adequately water your magnolia tree, especially during the first few years while the tree is becoming established.
Water under the entire canopy of the tree, not just around the trunk. Magnolia feeder roots usually extend out as wide as the tree.
Water slowly so the water does not puddle on top of the surface.
Water in the mornings if possible for better water retention. In addition, mulch around the tree with about 2 to 4 inches of mulch, such as pine needles or bark, to also help with water retention.
Water more frequently in the first two years after planting. In general, water your tree with about 15 to 20 gallons once a week for the first two years. Then for the third year, water your tree with 15 to 20 gallons twice a month. After the third year, water only when you are experiencing long dry spells, such as a month or more of little rain or when you notice the leaves wilting.