August 2024: Bigleaf Magnolia

Full form Bigleaf Magnolia (Magnolia macrophylla) at The Arboretum State Botanical Garden of Kentucky, Lexington, Kentucky. By Greg Doyle

This Bigleaf Magnolia (Magnolia macrophylla) is located along the path through the Appalachian Plateau section in The Arboretum.

This tree has the largest simple leaf and largest flowers of any tree indigenous to North America. Endemic to the Southeastern United States, this Magnolia is an iconic species in the mesic slopes of the Daniel Boone National Forest. The leaves are deciduous and the tree can grow to an average height of 40 feet with a 30 foot spread. The tropical looking leaves are green on top with a silvery-gray underside and, as the names indicate, can measure up to an astonishing 3 feet long and almost 1 foot wide.

Magnolia macrophylla ssp. macrophylla 961-89*A. Kyle Port

Blooming in late May through June, the large fragrant flowers put on an impressive display. Each dinner plate sized flower has 6 to 9 creamy white tepals with the inner tepals sporting a rose-purple blotch near the base. Like other magnolias, the flowers are primarily pollinated by beetles instead of bees or butterflies. In the late summer and early fall, the flowers give way to large cone-like fruits which upon maturity release bright red arils that are suspended on slender threads. These red arils are eaten by birds, which are the primary dispersal agent. 

​Bigleaf Magnolia grows best in situations that mimic its growing conditions in the wild, needing rich, moist well-drained

soils in full sun or partial shade. As such, it does not tolerate compaction, permanently wet soils, or prolonged droughts. This tree was named by the French naturalist Andre Michaux in 1789, but it seems to have been first documented in 1775 in Mobile, Alabama by the naturalist William Bartram. Dethroned in 2021, the former national champion Bigleaf Magnolia is located in Kentucky near the Red River Gorge, in an area that was never logged, called Tight Hollow. This former champion Bigleaf Magnolia tree measures 108 feet tall with a canopy spread of 42 feet.

Leaves of Bigleaf Magnolia (Magnolia macrophylla) at The Arboretum State Botanical Garden of Kentucky, Lexington, Kentucky. By Greg Doyle.​

Should you plant a Bigleaf Magnolia in your yard? If you have the right soil conditions, this tree would make for a fantastic specimen. As mentioned above, avoid planting in compacted soil or in places of soil moisture extremes. The large leaves also benefit from protection against strong winds as they are prone to tattering and breakage. Apply a healthy mulch ring (we suggest arborist wood chips) around this tree and maintain it to the dripline at least yearly. Leave fallen leaves in the fall to help build healthy and high nutrient soil around the root zone.