The Arnold Arboretum’s 281-acre landscape is a living museum, displaying plants sourced from all corners of the temperate world for conservation and study. To expand and refine these collections, staff participate in plant exchanges with sister botanical gardens and plant conservation partners, and whenever possible, collect seed directly from the wild. Recently, the Arboretum mounted a fall expedition in the US Midwest in search of naturally-occurring native plants to expand holdings and fill gaps in its collections inventory.
The documentation, or backstory, associated with each of the Arboretum’s accessioned plants—the 15,000 plus trees, shrubs, and vines that are recorded, mapped, and tracked by curatorial staff—is a good indication of its value to the Arboretum and science. Knowing precisely where a plant comes from can be important data to researchers. Wild-collected individuals carry the genetic characteristics of their source population, which can aid efforts to conserve and reintroduce threatened and endangered species to their habitats. For these reasons, the Arboretum has sent staff into the field—particularly throughout temperate Asia and North America—for more than a century in search of new species, as well as expand the genetic diversity of species already in cultivation.
This work continues to drive much of the Arboretum’s strategy for plant acquisition today, with renewed vigor since the opening of research facilities on the Arboretum grounds at Weld Hill. In late September, Curator of Living Collections Michael Dosmann was joined by former Curatorial Fellow Jonathan Damery to scout and collect woody plant species in southern Illinois and Indiana. In their five days in the field, the pair collected propagation material in the form of fruit and seed for 24 species, including hickory (Carya spp.) and maple (Acer spp.), two of six national collections held at the Arboretum for plant conservation. Among other compelling acquisitions are three new vine species for the Leventritt Shrub and Vine Collection—wild yam (Dioscorea quaternata), greenbriar (Smilax rotundifolia), and woodbine (Clematis virginiana)—as well as a native burning bush species, Euonymus atropurpureus. Voucher specimens including fruits were also obtained to document the species collected for the Arnold Arboretum herbarium.
“Each of the plants we selected in the field on this expedition was collected for a reason,” explained Dosmann, “whether to strengthen our core collections, acquire wild material lacking for certain species, or to add a new species to our inventory.” While the duo encountered many more fruiting plants on this expedition than those they collected, Dosmann stresses the importance of being selective in the face of such abundance. “Everything we collect for the Arboretum must be thoroughly documented, vouchered for the herbarium, and propagated and cultivated in our greenhouses and nurseries over a number of years. These requirements paired with limited space in our landscape to locate new plants makes limiting our scope to our needs a critical priority.”
The Arboretum has sourced many important historic collections from this region, ranging from plants gathered by Smithsonian ornithologist Robert Ridgway in the 1880s and Arboretum botanist E. J. Palmer [pdf] in the 1920s to an important 1979 expedition by Jack Alexander and Gary Koller. Due in part to the convergence of several river systems—the Wabash, Illinois, Ohio, and the Mississippi—the flora of southern Illinois is rich and includes the northern-most populations of species more typical to Southern ranges like Carolina silverbell (Halesia tetraptera) and American snowbell (Styrax americanus). Dosmann and Damery collected both of these species on this expedition, which will add value to the Arboretum’s holdings of these native trees.