Magnolia soulangeana, or saucer magnolia, features large, fragrant flowers with white and purple variegated petals. The trees bloom in the winter in southern climates and early spring in northern ones. Buy and plant saucer magnolia trees in the spring. While mature trees can grow up to 30 feet in height, this takes a number of years. Buy trees right before you intend to plant them, since they don't do well if left to sit unplanted.
Verify that you live in an area where the saucer magnolia grows, hardiness zones 4 to 9, by checking the USDA Hardiness Zone map (see Resources). If you live outside this area, the saucer magnolia will fare poorly and you should choose another type of magnolia.
Call local nurseries and garden centers to see whether they carry magnolia soulangeana trees. Since you know what type of tree you want to buy, calling to verify they have it is easier than driving around.
Visit the nursery and browse the selection of magnolia soulangeana trees. Select a tree that has a long, straight trunk and not a bent trunk. Look for a tree with one dominant leader branch rather than multiple leaders, or main branches.
Test the root quality by bending the tree trunk, pushing it to the side. Check to see if the trunk bends with the tree, forming a line, or if the trunk remains so the tree takes an arched shape. Purchase trees that make an arched shape, not a line shape, since the line shape indicates root defects.
Order a magnolia tree online only if you cannot find saucer magnolia trees in your area, yet are certain they grow well there. Since there's no way to test the quality when you order online, this should be a last resort.