Greenback Southern Magnolia is a cultivar of Magnolia grandiflora, a perennial tree valued for its glossy, evergreen foliage and large, fragrant flowers. The Greenback Southern Magnolia tree typically reaches 25 to 40 feet in height and 10 to 15 feet in diameter. The tree blooms during summer, producing creamy white flowers about 10 inches in diameter. Native to North America, Greenback Southern Magnolia thrives in zones 7 through 9 and grows in lawns and gardens throughout the United States.
Plant Greenback Southern Magnolia in a location that receives full sunlight throughout the day. Apply a 3-inch layer of organic compost to the planting site, and use a garden tiller to work the material into the soil prior to planting to increase fertility and drainage to adequate levels.
Spread a 3- to 5-inch layer of mulch over the area surrounding Greenback Southern Magnolia to insulate the soil, control weeds and improve moisture retention. Allow at least 3 inches between the base of the tree and the mulch to allow air to circulate and reduce the risk of rotting.
Water once per week during the first year of growth to help the tree establish its root system. Decrease the frequency of watering thereafter to once every 10 to 14 days, or whenever the top 3 inches of soil are completely dry.
Feed Greenback Southern Magnolia once per year, during early spring just as active growth resumes. Use a balanced 10-10-10 NPK all-purpose tree fertilizer to provide nutrition for root, foliage and flower formation. Apply according to the manufacturer's directions for the best results.
Prune the tree once per year during late winter, just before new growth begins. Use pruning shears to remove dead, damaged and diseased branches to improve the overall health of the tree. Cut back any excessively long or bare branches to encourage a thicker growth habit and increase the aesthetic appeal of the tree.