Southern Magnolia

Size, growth and what to expect

Southern magnolia grows at a medium pace, about a foot and a half a year in our growth estimator. Open-grown wild trees have kept up that rate to age 50. Expect 60 to 80 feet with a crown 30 to 50 feet wide.

Creamy white flowers 8 to 12 inches across open from April to June, with a few more through the summer. Each lasts two to four days and smells strongly of lemon. The cone-like fruit ripens from September into late fall, and its red seeds hang on silky threads before they drop. Squirrels, opossums, quail, wild turkeys and songbirds eat them.

It grows wild on the Coastal Plain from southeastern North Carolina to central Florida and west to eastern Texas. Its home is rich woods near streams, hammocks and wooded dunes. Birds carry its seed from planted trees, and it now grows wild well north and inland of that range.

How to grow Southern Magnolia

Southern magnolia grows best in part shade or full sun, in a rich, moist, well-drained soil on the acid side. It takes clay, sand or a slightly alkaline soil, and it stands salt spray, but not standing water or long flooding. At the cold end of its range, give it shelter from winter wind and sun. Its roots spread far wider than the crown, and now and then they lift a curb or walk. Plant it 25 feet from a wall and more than 50 feet from overhead wires, and set trees 30 feet apart.

Saplings ship potted. Magnolia roots are thick and fleshy, and moved trees recover slowly, so plant in late winter or spring rather than in fall. Cut any roots that circle the root ball, since magnolias are prone to girdling roots. Dig a hole wider than the root ball and no deeper, and set the root flare about 2 inches above the surrounding soil. Put the native soil back in, and keep a wide ring of mulch clear of the trunk. Rub the red coat off the seed, and never let it dry. Sow it outdoors in fall, half an inch deep, under hardware cloth against mice. For spring, hold it damp in the refrigerator for two to three months first.

Water weekly through the first two summers, then in dry spells for three to five years, until the roots are established. Frost can kill young seedlings, so shelter them through their first winters. Deer browse it only moderately. Prune after it flowers, during the growing season, since cuts made while it is dormant heal poorly. Leave the low branches on if you can.

Each flower carries both male and female parts, and beetles and bees carry the pollen. Isolated trees are known to bear cones with seed, so a lone tree can set seed. Seed-grown trees can take ten years or more to flower, and the best seed crops come from about 25 years. Heavy infestations of magnolia scale can kill branches, and leaf spots are common but seldom serious. Old leaves drop in spring and fall and are slow to rot.