“Stop! We’re here!” directed Kea Woodruff, who was navigating from the passenger seat of our rented vehicle. Woodruff was then the Arnold Arboretum’s plant growth facilities manager. We were on day three of a 2018 plant-collecting expedition to Arkansas and Oklahoma—part of the Arboretum’s Campaign for the Living Collections—and we were driving up Highway 62 in northeastern Arkansas, approaching the Missouri border. Months prior, we reached out for guidance on our Ozark-specific taxa list to the Arkansas National Heritage Commission. They provided an account of a particular population of corkwood (Leitneria floridana), a rare shrub sparsely endemic to the southeastern United States. We dropped a Google pin on the approximate location of their 2003 description and hoped that no habitat loss occurred between then and October 2018. I steered onto the shoulder, and we began scouring the nearby flora as traffic whizzed by.
After what seemed like only a moment, Woodruff pointed to a promising-looking stand. “Wait,” she inquired, “isn’t that it?” Corkwood is a striking plant, and we were able to confirm it in short order. It is monotypic (the only species in its genus) and is in a mostly tropical family, Simaroubaceae. The most well-known and recognizable temperate member is the tree of heaven (Ailanthus altissima), a noxious urban weed. The noninvasive, but just as conspicuous, corkwood typically grows five to ten feet tall—although it can reach up to twenty feet. It is adorned with elliptic olive-green leaves that are glossy, leathery, and crowded toward branch tips. The common name derives from the buoyancy of the wood. It is one of the lightest woods known and has been used to float fishing nets. The bark is a deep reddish-brown with lenticels. Corkwood is content to sucker and form thickets, particularly in its ideal environment: forested swamps and flooded soils.
The Arboretum’s inaugural corkwood plants (accession 5336) arrived from botanist Benjamin Franklin Bush, who sent plants in 1894, just two years after he had first documented the species in southeastern Missouri. (The species had been named, in 1860, by Alvan Wentworth Chapman, based on populations in the estuary of Florida’s Apalachicola River.) The plants prospered along Meadow Road, in a location affectionately known as “Leitneria swamp,” where water accumulates and persists throughout most of the year. Eventually, this accession became indistinguishable from other corkwoods that were planted around 1970, and the mixed planting was given a new accession number (244-97). Plants from Taylor County, Florida, were later added to the location (accessions 29-96 and 30-96). The species is near threatened in the wild and remains in several Florida and Texas counties abutting the Gulf, and a few inland ones in Arkansas, Georgia, Mississippi, and Missouri.
Woodruff and I were determined not to let several feet of muck act as a deterrent. I repurposed two herbarium voucher bags as waders and bounded in. As we had anticipated, we found no fruit. The olive-sized brown drupes are borne in clusters of two to four near branch tips, below the foliage. Corkwood is dioecious, having separate male and female plants. Flowers are axillary catkins approximately one-and-a-half inches long. This colony could have been a single sex, or perhaps voracious critters beat us to the fruit. Plan B consisted of combing for small suckers. We dug three, which we bagged and labeled as puzzled drivers drove past.
From there, we continued to the nearest FedEx location, where we were grateful for the kindness of strangers. After we explained that we hailed from Boston and were in the midst of an expedition, the store clerks were keen to facilitate packaging in the tallest boxes they had available. The plants arrived the next day at the Dana Greenhouse, where they were potted and catalogued (accession 278-2018). In April 2020, the three individuals were planted in the seep on Bussey Hill—this time a location distinct from any others. I hope these plants will colonize the seep over the next decade, just as the original collection has done to the Leitneria swamp.
Tiffany Enzenbacher is the manager of plant production at the Arnold Arboretum.
Citation: Enzenbacher, T. 2021. A temperate cousin: Leitneria floridana. Arnoldia, 78(4): 48–49.