The Southern magnolia is a popular tree in southern gardens thanks to its large, fragrant flowers. Many varieties of this magnolia exist, some forming dense pyramidal shapes while other types featuring large spaces between the branches. In 1986, the American Forestry Association awarded one of the largest magnolia trees in Smith County, Mississippi with the title of "National Champion"---the tree reached 122 feet with a trunk diameter of 6 feet. A native North American evergreen, the southern magnolia is the state tree of Mississippi, but it makes a great addition to any Southern landscape.
Southern magnolia typically grows to 80 feet high and up to 40 feet wide, requiring some thought as to whether or not it fits available garden space. For best results, the tree thrives in USDA hardiness zones 7 through 10. While the tree is native to the American South, cultivars of this tree may be grown in just about any state as long as the tree receives plenty of water in drought or dry conditions. In colder climates, the tree's growth rate is much slower, with the plant growing into more of a bush than a tree. Although it prefers acidic soil, a southern magnolia will grow in a wide variety of soil types as long as the tree receives plenty of water until it reaches three to five years in age.
Magnolia trees grow in a variety of soils as long as the soil is well-drained. Small trees found growing naturally work best for transplanting, ideally in the late fall and winter. Seeds from the magnolia cone may also be planted after they've soaked in water for a few days. The seeds are ready to be planted after they've been stored at a constant temperature of about 45 degrees Fahrenheit for three months.
Watering and Mulching
Newly planted young trees require plenty of water for the first three to five years, until they are well established. They also require plenty of shade during those initial years to protect from hot, dry summer days. Adding a few inches of mulch around the base of the tree, about 1 inch away from the trunk, is critical to the health of the tree. Mulch helps retain moisture while keeping the soil around the roots cool. Decomposed leaves of magnolias make a great mulch.
Fertilizing and Pruning
The trees thrive when they receive natural, organic fertilizer such as cottonseed meal, bone meal, fish scraps and cow manure. Fertilizer should be applied in January or early February. Transplanted seedlings do not require fertilizing during their first year. The tree requires little pruning---if left to grow naturally, the branches eventually gracefully sweep to the ground. Remove wind-damaged branches to prevent disease.
Pests and Diseases
Scales of various types may infest the branches and leaves of the Southern magnolia. While the tree may not look its best when that occurs, the tree should continue to grow without any treatment. The leaves may get blights or black mildews caused by fungi. To avoid the problem the following year, gardeners simply rake up and dispose of the infected leaves.
Weevils sometimes feed on the leaves, but that will not destroy the tree. Magnolia borers may be a problem with young trees; an insecticide may be able to control the problem.