Scientific Note: Quercus sinuata Walter—the Hybrid of Q. falcata and Q. phellos—Rediscovered and Neotypified

The name Quercus sinuata, published by Thomas Walter in 1788, has been interpreted to apply to some species of oak native to the southeastern United States, most often the Bluff Oak (Q. austrina Small). Inspection of the vegetation in the immediate vicinity of Walter’s North Carolina homesite disclosed no Bluff Oak, but did reveal several trees that well matched Walter’s description. Specimens from these trees have been identified as the hybrid of the Southern Red Oak (Q. falcata Michx.) and the Willow Oak (Q. phellos L.), both of which were found at the same location. To provide stability to the name Q. sinuata, a neotype has been selected. In the second half of the 18th century Thomas Walter, an English expatriate, maintained a home and plantation on the Santee River, Berkeley County, South Carolina. In 1788 Walter published his Flora Caroliniana, a record of the plants he had encountered, matching many as best he could with those in the books of Carl Linnaeus, and including others that he believed to be new. His modest volume, the first flora published in America to follow the new Linnaean system of binomial nomenclature, contained 436 genera and approximately 1050 species. For each species he gave a brief diagnosis in Latin and a two-part Latin name. Walter described 13 species of Quercus, the oaks. Most are readily recognized: Q. sempervirens Walt. (5Q. virginiana Mill., Live Oak), Q. phellos L. (Willow Oak), Q. humilis Walt. (5Q. incana Bartr., Blue-jack Oak), Q. prinus non L. (5Q. michauxii Nutt., Swamp Chestnut Oak), Q. nigra non L. (Q. marilandica Muench., Blackjack Oak), Q. aquatica Walt. (5Q. nigra L., Water Oak), Q. rubra non L. (5Q. falcata Michx., Southern Red Oak), Q. laevis Walt. (Turkey Oak), Q. alba L. (White Oak), Q. lyrata Walt. (Overcup Oak), Q. villosa Walt. (5Q. stellata Wangenh., Post Oak). These determinations are in agreement with conclusions of a recent careful study of Walter’s oaks (Wilbur 2002). One of Walter’s oaks is less clear. The Running Oak, a shrubby, rhizomatous species, has been known since its publication as Quercus pumila Walt. Recently Wilbur (2002) has argued that Walter’s diagnosis was inadequate and that a new name was required; he supplied the need with Q. elliottii Wilbur. Walter had described the lower leaf surface as glaucis. Wilbur is correct in noting the lower surface is densely gray-puberulent, not glaucous. But Walter, probably lacking adequate magnification, can be forgiven for interpreting the gray lower surface as showing glaucescence. Granting this reasonable latitude, Walter’s description fits the Running Oak quite well. Further, Wilbur’s dismissal of Q. pumila leaves Walter’s work without a name for the Running Oak, a plant he could not help but have known in the dry oak-pine habitat adjacent to his Santee River home. Yet another of Walter’s oaks has continued to puzzle later workers. He named this species Quercus sinuata, with the diagnosis ‘‘foliis sinuatis laevibus obtusis supra pallidis, subtus subglaucis, glandibus mediocribus globosis calyce subplano’’ (i.e., leaves sinuate-margined, obtuse, pale above, subglaucous beneath, the