Thompson Mills Forest & State Arboretum

Located on 337 acres near Braselton, Georgia, in Jackson County, Thompson Mills Forest was designated in 1991 as the State Arboretum of Georgia. It’s home to nearly 200 native tree species found in Georgia, as well as woodland trails and a unique granite outcrop that’s home to several threatened plant species.

Property history

The property was donated to the Georgia Board of Regents in 1980 by Lenox Tom Thornton to provide teaching and research opportunities to students and faculty in dendrology, ecology, silviculture and forest biology. Thornton also saw the land as an opportunity to establish an arboretum of native and exotic trees, which would provide Georgia residents and others the opportunity to visit and study the variety of flora from the region.

Thompson Mills Forest was named for the Thompson Mills Community located in this area, a prominent plantation and agricultural community that, by a 1910 account, included a large store, a gin, a flour mill, orchard, large barns and many homes for tenant farmers. In the early 1900s, the U.S. Department of Agriculture conducted cotton breeding experiments at the site, and government scientist H.A. Allard had amassed more than 100 species of rare plants during his time there.

This tradition on the property continued after Mr. Thornton donated the land. He made the donation out of gratitude for Warnell professor Claud Brown who, as a timber procurement forester in the 1950s, helped Thornton and his mother, Eva Thompson Thornton, develop and implement a forest management plan for their property.

Plant collections

In the years since the land was donated, Warnell faculty, students and staff have had a tremendous influence on the property. Brown acquired tree seeds from all over the world, starting them in nursery beds at Whitehall Forest and then transplanting them at Thompson Mills. Many of these trees, all native to Georgia, were also photographed by

Brown and used in the book “Native Trees of the Southeast,” which he co-authored with Kay Kirkman. One of Brown’s goals was to include specimens of every one of the 215 tree species native to Georgia.

He got close—from 1980 to 1987, more than 100 species of native Georgia trees were grown from seeds and planted at the arboretum, most by Brown and Bill Lott, former arboretum director who retired in 2020. These trees, along with the 80 indigenous species already on the property, added up to 194 of the 215 native tree species in Georgia. By last count, the arboretum was 12 species short of having an example of every native tree.

Thompson Mills Forest also contains several planted collections, including the Eva Thompson Thornton Memorial Garden and the Pinetum and Conifer collection.

Eva Thompson Thornton Memorial Garden

This memorial garden was established in 1991 on 8 acres. It includes a commemorative plaque and a small pavilion with restrooms near the entrance. It includes a collection of more than 100 native and ornamental trees and shrubs, including:

• Conifers from around the world, including Nordmann fir, Chinese fir, sugi, Atlantic white cedar, blue spruce, Apache pine and dawn redwood
• Yellowwood
• Oaks of Georgia and adjacent states, including the rare Georgia and Oglethorpe oaks, turkey oak, bluejack oak and running oak from the sandhills, swamp chestnut oak and cherrybark oak from bottomland forests
• Yellow, red, Georgia and bottlebrush buckeyes
• A toothache tree (Zanthoxylum clava-herculis)

Pinetum and Conifer collection

The pinetum and conifer collection includes trees from around the world collected by Brown. He obtained seeds of more than 200 gymnosperms from 20 countries in North America, Europe and Asia, then germinated and transplanted them to the pinetum and nearby areas of the forest. 

While not all of the conifers planted by Brown have survived over the years, the collection of exotic conifers adjacent to the pinetum is unique to the Southeast and contains more than 100 specimens of gymnosperms from 27 countries.

Trees in the collection include:

• Multiple examples of every pine species native to Georgia: loblolly, slash, longleaf, shortleaf, sand, spruce, table mountain, pitch, pond and Virginia
• Conifers, adjacent to the pinetum, featuring deodar, Atlas and Lebanon cedars, plus Douglas fir, red spruce and members of the Cupressaceae (Juniperus, Chamaecyparis, Thuja, Calocedrus and Taxodium)

Additional features

Thompson Mills Forest also features several miles of trails that weave throughout the property, with labels identifying specimens of native trees. The property is also home to an 8-acre granite outcrop on a forests ridge, which supports several unique plants. These include Confederate daisies and three federally protected species rescued from other sites and re-established at Thompson Mills Forest: black-spored quillwort, mat-forming quillwort and little amphianthus.