This species boasts the largest simple leaf and single flower of any native plant in North America. Surprisingly, it’s an understory tree usually between 45 and 60 feet tall. 
Any disturbance that lets more light reach the ground is beneficial to the establishment of Big-Leaf magnolia, but despite its relatively fast growth-rate when stimulated by more light, other understory and canopy trees/seedlings are usually able to outgrow and out-compete it. This suits the plant just fine as it is tolerant of low light levels. 
In the southeastern United States, especially Alabama and surrounding areas, Magnolia macrophylla is sometimes called the “cowcumber magnolia,” in contrast with the much smaller-leaved Cucumber Magnolia. 
Identification and Description
Big-Leaf Magnolia is a deciduous, flowering tree having coarse texture, a round-headed form, and a medium growth rate. Unusually large leaves are 20 to 30 inches long and 8 to 12 inches wide. Large, white, fragrant flowers are borne from May to June and have six petals 8 to 12 inches across. Its egg-shaped, cone-like fruit and red seeds are typical of Magnolias. 
Adapted to Georgia hardiness zones: 7a, 7b, 8a. Atlanta is zone 7b 
For more photos and identification help, we recommend the UGA Extension site: Native Plants for Georgia Part I: Trees, Shrubs and Woody Vines (B 987).