Plants of the USA: recordings on native North American useful species by Alexander von Humboldt.

Background: The German naturalist Alexander von Humboldt conducted an expedition through the American continent, alongside Aimé Bonpland, from 1799 to 1804. Before finally returning to Europe, they decided to take a side trip to the USA between May 20 and July 7, 1804. Humboldt's most detailed account of his time in the USA consists of a manuscript entitled "Plantae des États-Unis" (1804), containing information on useful plants and timber of the country. The aim of this paper is to retrieve, for the first time, ethnobotanical information regarding North American plants and their uses inside this Humboldt's manuscript as well as to highlight the erasure and invisibilization of North American Indigenous knowledge within historical documents and bibliography, mainly during the nineteenth century.

Methods: "Plantae des États-Unis" (digitized version and its transcription) was carefully analyzed, and information on plant species mentioned in the manuscript (including botanical and vernacular names, traditional uses, and general observations) was retrieved. Traditional uses were correlated with ethnobotanical data from the Native American Ethnobotany Database and encyclopedic literature on North American plants from the nineteenth and early twentieth centuries, as well as recent pharmacological studies searched in scientific papers.

Results: In the manuscript are mentioned 28 species distributed in 15 botanical families, with Fagaceae (9 Quercus species) being the most representative. All species are USA natives, except for one undetermined species (only the genus was mentioned, Corylus). Four species were directly mentioned as medicinal (Toxicodendron radicans, Liriodendron tulipifera, Actaea racemosa, and Gillenia stipulata), while other four were described as tanning agents (astringent) (Cornus florida, Diospyros virginiana, Quercus rubra, and Quercus velutina). Two species were described as bitter (Xanthorhiza simplicissima and A. racemosa). Nine Quercus species were described, but five were reported as the most useful oaks for cultivation in Europe (Quercus bicolor, Quercus castanea, Quercus virginiana, Quercus michauxii, and Quercus alba); three of them were used for ship construction (Q. virginiana, Q. michauxii, and Q. alba), two as astringent (Q. rubra and Q. stellata), and one had wood of poor quality (Quercus phellos). One species was described as a yellow dye (Hydrastis canadensis), and the other was mentioned as toxic (Aesculus pavia). Ten species did not have any useful applications listed.

Conclusions: Although "Plantae des États-Unis" is a brief collection of annotations, these data reveal a historical scenario of outstanding plants with social and economic interest in the USA at the beginning of the nineteenth century. The data highlight a clear process of suppression of the traditional knowledge of Native North American Indigenous peoples in past historical records and literature, due to the lack of acknowledgment by white European settlers and American-born explorers. This ethnobotanical inventory may help us understand the relationship between plants and Native North American Indigenous peoples, as well as European naturalists and settlers, and USA-born people in the past, and reflect on the importance of Indigenous traditional knowledge, bioeconomy, sustainable management, and conservation of biodiversity in the present and future.