I often get questions about superlatives: which accession is tallest, widest, oldest? The last I can answer in several ways: A bonsai, Chamaecyparis obtusa ‘Chabo-Hiba’ (877-37*A), which began its training in 1737, is our absolute oldest. One Quercus alba (346-2010*A) on Peters Hill is about 220 years old, germinated in place long before the parcel’s acquisition. The oldest in-ground accession, brought from elsewhere, is 245-46*A, Buckleya distichophylla.
Native to the Blue Ridge Mountains of Tennessee, North Carolina, and Virginia, the piratebush is at moderate risk of extinction because its few populations are under threat from habitat loss and the decline of host species. Host species? Yes, this member of the Santalaceae is a hemiparasite. Although fully capable of photosynthesis, its roots parasitize other species to better acquire nutrients and sugars.
Our shrub has grown among the hemlocks on their eponymous hill since accessioning in 1946. Its Harvard history goes deeper, however. Asa Gray acquired it in 1843 during an excursion to Southern Appalachia. The plant grew in the Harvard Botanic Garden until the garden’s extinction. That the plant—a centenarian then—survived transplant to its new environment is a testament to its tenacity, and to the determination of the collections staff.
In nature, one of piratebush’s hosts, Tsuga, is under threat from Hemlock Wooly Adelgid, an introduced insect pest. For over 25 years, the canopy of Hemlock Hill has been under the same threat. We’ve stabilized the hemlocks, but the environment has shifted since Ethan Johnson took the photo decades ago. As crowns thinned and neighboring trees died, the conditions around the Buckleya worsened. Shade cloth and supplemental watering have ameliorated some challenges, and this spring we transplanted a young Tsuga canadensis into its root zone to re-establish ties to the community.
There are different forms of extinction: loss of an entire biological lineage—a species—as well as the extinction of an individual, independent lineage like this plant. Should it die without issue, we would lose something special—a plant touched by many who have come and gone. Collected by Gray, observed by Charles Sargent who curated the campus garden, vouchered by John Jack, written about by Richard Howard, visited by countless others. It is a throughline passing across Arboretum history. In either case, extinction cannot be an option.
Michael S. Dosmann is keeper of the living collections at the Arnold Arboretum.