They are considered icons of the U.S. South, but magnolia trees generally do quite well in California. Winter cold can be a limiting factor for magnolias grown in California; they won't survive in the Sierra Nevada or colder mountainous or foothill areas. Intensity and timing of late winter or spring frosts are other considerations, because frost can damage the spring bloom--and stunning, often fragrant flowers are key reasons for growing magnolia. Consider growing magnolia trees if you live in well-watered areas of southern California, along warmer sections of the California coastline and almost anywhere in the Central Valley and its very low foothills.
Select a suitable planting site in full sun or partial shade, with adequate room for the full-grown tree. Most magnolias do best in rich, moist but well-drained acidic soil--ideal pH is 5.0 to 6.5--yet some, including the southern magnolia, can gradually adapt to drier soils. Sweetbay or swamp magnolia can tolerate wetter soils than most.
Plant evergreen magnolias, including southern and sweetbay magnolia, early in the spring. Deciduous magnolia varieties can be planted either in spring or autumn, although spring is preferable in northern California.
Cultivate deeply to loosen and prepare the planting bed. Add several inches of compost or leaves to the entire bed and dig deeply again, to thoroughly mix soil and organic matter. Dig the planting hole, no deeper than the magnolia's root ball but twice as wide.
Carefully slip the root ball out of the container and place it in the center of the hole. The top of the root ball should be even with the surrounding soil level. Fill the hole with displaced soil, covering roots and firming soil around them.
Water deeply to settle the soil, thoroughly saturating the entire root area. Irrigate every few days for the first few weeks, to minimize transplant shock. Irrigate young trees regularly until they are well established, or three to five years.
Mulch to conserve soil moisture and moderate soil temperatures. Drop loose pine needles by the handful, letting needles fall naturally just as they would in a forest. Apply mulch about four inches deep, making sure none comes within several inches of the trunk. Water thoroughly to settle the mulch into a protective mat.