In the “Plantae des États-Unis” manuscript are mentioned 28 species distributed in 15 botanical families, being Fagaceae (9 species) the most representative, followed by Ranunculaceae (3 species), Magnoliaceae, Salicaceae and Sapindaceae (2 species), and Anacardiaceae, Betulaceae, Bromeliaceae, Cornaceae, Cupressaceae, Ebenaceae, Juglandaceae, Lauraceae, Poaceae, and Rosaceae (1 species). All species are USA natives, except for one undetermined species (only the genus was mentioned, Corylus).

Four species are directly mentioned as medicinal (Toxicodendron radicans (L.) Kuntze, Liriodendron tulipifera L., Actaea racemosa L., and Gillenia stipulata (Muhl. ex Willd.) Nutt.), while other 4 are described as tanning agents (astringent) (Cornus florida L., Diospyros virginiana L., Quercus rubra L., and Quercus velutina Lam.), a property related to tannins, which can be used for medical purposes too. Two species are described as bitter (Xanthorhiza simplicissima Marshall and A. racemosa), which can be correlated to tonic properties. Nine Quercus species are described, but 5 were reported as the most useful oaks for cultivation in Europe (Quercus bicolor Willd., Quercus castanea, Quercus virginiana Mill., Quercus michauxii Nutt., and Quercus alba L.). Three of them are used for ship construction (Q. virginiana, Q. michauxii, and Q. alba), 2 as astringent (Q. rubra and Q. stellata), and 1 highlighted as having wood of poor quality (Quercus phellos L.). One species is described as a yellow dye (Hydrastis canadensis L.), and the other is mentioned as toxic (Aesculus pavia L.). Thirteen species did not have any useful applications listed. The entire inventory of “Plantae des États-Unis” is described in Tables 2 and 3.

The results of this work bring to light knowledge that had been hidden within an unanalyzed document in the field of Historical Ethnobotany. This branch of science emerges as a prominent discipline, focusing on the study of historical human–plant relationships, primarily through the analysis of written historical documents such as publications, manuscripts, official records, prescriptions, as well as iconographic sources and voucher specimens in herbaria [38,39,40].

In recent years our research group has investigated the historical and ethnobotanical legacies of many naturalists and propagandists regarding South American biodiversity [23, 24], especially Humboldt’s travel journals, manuscripts, and books [22]. Our findings confirm that this manuscript “Plantae des États-Unis,” written by Humboldt, is a valuable source of information on North American plant species of the nineteenth century.

The most sensitive issue is that the information reported by Humboldt was provided by prominent North American naturalists, as annotated in the manuscript. However, it did not come directly from sources reporting the original inhabitants of America—hundreds of North American indigenous tribes—nor did these naturalists acknowledge the traditional knowledge of Indigenous peoples regarding biodiversity.

It is important to clarify that North American biodiversity has been systematically studied by naturalists from the perspective of European settlers since the sixteenth century, and later under the sight of white American-born explorers, but not from the Indigenous peoples’ point of view, even though they had interacted with nature for millennia and had a deep understanding of the medicinal, edible, and other uses of plant species, as well as the locations for collecting them and the methods for cultivating certain species.

The first book on North American plants was very well illustrated by the Frenchman Jacques Philippe Cornut (1606–1651). Other naturalists arrived earlier on the new continent, such as the Britishmen Thomas Hariot (1560–1621) and the artist John White (died around 1593), sent by Sir Walter Raleigh, and John Lawson (circa 1650–1711) in the USA; the Frenchmen Michel Sarrazin (1659–1734) and Jean-François Gaultier (1708–1756) in Canada; the French Pierre‑François-Xavier de Charlevoix (1682–1761), the British Mark Catesby (1682–1749) and the Swedish Pehr Kalm (1716–1779) in USA [41]; French father and son, André Michaux (1746–1803), and François André Michaux (1770–1855); Englishman Thomas Nuttall (1786–1859); the Scottish John Leigh Bradbury (1768–1823); the Turkish-born Constantine Samuel Rafinesque (1783–1840) [42], among many others.

The first well-documented expedition sponsored by the USA government was that conducted by Meriwether Lewis (1774–1809) and William Clark (1770–1838). After the Louisiana Purchase in 1803, President Thomas Jefferson, a very enthusiastic man in science that had been planning such a trip since 1783, gathered efforts in Congress to finance an expedition to make reports on the geography, soils, plants, and animals [42]. Other important American expeditions were conducted by USA-born naturalists such as John Bartram (1699–1777) and his son William Bartram (1739–1823) [43]; Thomas Freeman (died in 1821) and Peter Custis (1781–1842) in 1806, and Zebulon Montgomery Pike (1779–1813) in 1805 and then 1807 [42].

Unfortunately, indigenous peoples have been eclipsed in the historiography of the production and circulation of knowledge and technologies since the beginning of Natural History expeditions [44]. The indigenous erasure was motivated by a desire to remove indigenous peoples in order for the settlers to access resources and land. American Indians were not only removed geographically through reservations by forced treaties defined by white men and biologically through genocide, but also culturally and politically, and they were classified by settlers in a way to further erase and eliminate their existence [45].

Settler colonialism destroys to replace [46]. This is evident in this work where vernacular names are all written in English or French in Humboldt’s manuscript, with no indigenous references to traditional uses. As Wolfe [46] argues, renaming indigenous names is a way of cultural erasure and it means the imposition of settler colonialism. Another example refers to generalization: when we analyze encyclopedic literature on North American useful plants between the eighteenth and nineteenth centuries, authors mention indigenous peoples simply as “Indians” or “Natives,” without discriminating between specific tribes or nations. Wolfe [46] comments with an example on black people, which were racialized as “slaves,” and slavery constituted their blackness. Correspondingly, Indigenous North Americans were not killed, driven away, romanticized, assimilated, fenced in, bred White, and otherwise eliminated as the “original owners of the land” but simply as “Indians” [46].

In a different manner than the naturalists who preceded and even succeeded them, Humboldt and Bonpland described medicinal and useful plants in field journals during their voyage through South America, Mexico, and Cuba, often giving the Spanish and/or indigenous names, describing the preparation and use of the plants and sometimes giving tips on how to cultivate that plants and how to obtain advantages through plant breeding [22]. They obtained this knowledge directly from the indigenous population and other locals during longer sojourns in settlements such as missions and plantations. During his few weeks in the USA, however, Humboldt moved exclusively in the circle of scholars and the upper society. His information about useful and medicinal plants was therefore filtered through conversations with and publications by European Americans. Indigenous names of the plants are missing, as is information on the use of the plants by Native Americans.

Good examples are the properties of the plants Liriodendron tulipifera, Actaea racemosa, and Zanthorhiza apiifolia (Xantorhiza simplicissima) that Humboldt wrote down on top of the first page of his notes. He obtained this knowledge from an essay by chemist James Woodhouse, with whom he also met in Washington [47]. Woodhouse describes, in particular, the numerous experiments carried out with Xanthorhiza, which certainly also stirred the interest of the plant physiologist Humboldt. Through this form of presentation, Woodhouse gives the impression that he had discovered the properties of this plant as a dye and medicinal agent. The author ignores the already established use of the plant by Native peoples, such as the Cherokee in the Appalachians as well as European settlers [37]. Subsequently, this information is missing in Humboldt’ notes.

Analyzing and comparing the ethnobotanical information collected in “Plantae des États-Unis” with North American ethnobotany databases, it is possible to observe that much of this knowledge is similar to what Humboldt recorded, clearly showing a systematic suppression of Native peoples’ knowledge from historical records and medicinal plant literature. When historical literature does not acknowledge the original owners of this knowledge, it becomes evident as cultural appropriation. As stated by Colenbaugh and Hagan [37], settlers perceived Indigenous cultural institutions as inferior, systematically substituting native cultural traditions—such as hairstyles, attire, dances, and languages—by forcibly “educating” them in Euro-American subjects. However, the settlers consistently adopted Indigenous cultural precedents, particularly the uses of native resources for their own survival and livelihood, including medicinal, edible, woody, and many other useful plants [37]. The settlers translated and altered the natural environments they observed, simplifying them to fit colonial needs, concerns, and economic interests. In so doing, plants became material resources and objects of knowledge that continue to be used to produce Western herbalism as a predominantly white settler modality of medicine [48].

Besides Woodhouse, Humboldt also obtained information from the botanist Muhlenberg in Lancaster. In his diary, Muhlenberg mentions Humboldt’s visit on June 16, 1804, and particularly points out their exchange on oak trees [49]. However, the most distinguished authority was President Thomas Jefferson himself. In his “Notes on the State of Virginia,” Jefferson lists many North American native species, categorizing them as medicinal, edible, ornamental, and useful for fabrication, in his own words, “those which would principally attract notice.” Some of these species mentioned by Humboldt in “Plantae des États-Unis” include Aesculus pavia, Cornus florida, Liriodendron tulipifera, and Tillandsia usneoides as ornamental; Carya illinoensis and Diospyros virginiana as edible; Actaea racemosa as medicinal; and Quercus alba, Q. michauxii, Q. phellos, Q. rubra, Q. velutina, Q. virginiana, Salix nigra, and Taxodium distichum as useful for fabrication. Jefferson also cited many other species belonging to these same genera of species in Tables 2 and 3, such as Acer, Arundo/Arundinaria, Magnolia, Populus, Quercus, Rhus/Toxicodendron, and Salix, showcasing the diversity of useful species in the USA and the importance of these plants for the country [14, 50, 51]. The mention of these much-discussed native plants by Jefferson and Humboldt alike echoes their conversations on the local flora in June 1804.

Consulting the Native American Ethnobotany Database [26] and encyclopedic literature on medicinal plants from the USA in the nineteenth and early twentieth centuries, we will discuss the historical uses and context of these species from “Plantae des États-Unis,” focusing on the medicinal properties of these plants, complementing current scientific information about them.

Actaea racemosa, known as black snake root or black cohosh, was used by Indigenous peoples to treat plague and fevers, acting as sudorific, and even cure yellow fever [29], this last one the same indication of Humboldt. The febrifuge activity was evidenced by Wang et al. [52], when rhizome extract and the isolated compound cimicifugamide showed antipyretic and sudorific activities, acting both as agonists on beta-adrenergic receptors.

Roots of A. racemosa were also used by Native Indigenous peoples (Cherokee, Delaware, Iroquois, Micmac, and Penobscot) in the form of decoctions against snake bites and to treat acute and chronic rheumatism, in gargle for sore throat and treatment of smallpox and for digestive disorders as tonic, fevers, tuberculosis, and bronchitis [30, 32, 53]. Cherokee used root infusion for rheumatism, coughs, and colds [54], as well as analgesic, diuretic, and laxative [26]. Delaware people used it as tonic; Iroquois people used infusion of roots to “promote the flow of milk in women” and as blood purifier; Micmac and Penobscot used roots for kidney trouble [26].

In the past, A. racemosa was used for the treatment of menstruation disorders like amenorrhea and dysmenorrhea, and as a substitute of ergot during parturition favoring labor and after delivery relieved the after-pains (antispasmodic), puerperal mania and convulsions. By another way, large doses could be toxic causing sedation, vertigo, dilatation of pupils, and even abortion during pregnancy [30, 32]. Cherokee used the root to stimulate menstruation [54]. Curiously, nowadays A. racemosa is one of the most studied and prescribed plants for treatment of symptoms during menopause [55, 56].

Liriodendron tulipifera, known as the tulip tree or poplar, had the root and trunk barks as well as green seeds used as a febrifuge, with a similar effect to Cinchona (Peruvian bark or quina) for intermittent fevers by the native Osage and Cherokee peoples [26, 29, 31]. It used to be associated with Cornus florida to treat intermittent fevers [32]. The antimalarial and febrifuge activities were evidenced by Graziose et al. [57], who isolated aporphine alkaloids and sesquiterpene lactones from barks and leaves, respectively, with antiplasmodial activity in vitro. Furthermore, the alkamide tulipiferamide A isolated from barks inhibits NF-κB activation, resulting in the suppression of inflammatory mediators, including iNOS, COX-2, IL-1β, TNFα, and IL-6 [58].

Moreover, the bitter barks (roots and trunk) of L. tulipifera were used as tonic, stimulant, and diaphoretic and for the treatment of intermittent and chronic rheumatism as well as digestive disorders [30,31,32]. Vermifuge properties of the bark were well known by the Cherokee and the Osage [26, 29, 31]. Cherokee knew the medical properties of barks for dispepsy, dysentery, pinworms, cholera, coughs, rheumatism, wounds and boils, snakebite, hysterics (sedative), and weakness (tonic stimulant) [26, 54]. Wood was employed as lumber, to make long canoes and cradles, and as pulpwood by Cherokee. Rappahannock chewed the green bark as a stimulant [26].

In the USA, a full teacup with a strong infusion of Toxicodendron radicans aerial parts was used to be administered as a stomach stimulant, sudorific, and diuretic, and also for pulmonary conditions [33]. In England, the species was introduced in 1640, but the first medicinal use was reported in 1798 for the treatment of herpetic eruptions and also for other eruptive diseases, paralysis, rheumatism, and amaurosis [30, 33]. Regarding medical use reported by Humboldt, fresh parts (leaves, stems, and roots) of Toxicodendron spp. were used to prepare ointments and lotions by North American Indigenous peoples to treat skin diseases. Leaves of T. radicans are traditionally employed for the treatment of furuncles and skin eruptions [34]. Kiowa people used the plant for running or non-healing sores, rubbing the leaves over boils or skin eruptions, while Houma nation employed decoction of leaves as a tonic and “rejuvenator,” and Cherokee as emetic [26].

Some species of Toxicodendron, such as poison ivy (T. radicans), are considered to be toxic due to the presence of urushiols and derivatives, compounds that cause hypersensitivity reactions. Symptoms of dermatitis include acute eczematous eruptions characterized by streaks of intensely pruritic and erythematous papules and vesicles [59]. Navajo tribe considered the plant toxic, using it to poison arrows, while Thompson avoided it because it caused skin irritations and temporary blindness [26]. Furthermore, the latex is used as indelible ink for making linen and as an ingredient in liquid dressings and varnishes for finishing boots and shoes [30, 33].

Humboldt recorded Gillenia stipulata as having the same properties of roots of ipecacuanha (Carapichea ipecacuanha (Brot.) L. Andersson), a very important and traded South American medicinal plant in the eighteenth and nineteenth centuries due to its emetic and amebicide actions [36]. Johnson [32] reported the same observation, highlighting the vomiting effect of G. stipulata was less intense than ipecacuanha; in small doses it would act like stomach tonic.

The four species discussed above were included in the first edition of the United States Pharmacopoeia (USP) published in 1820. Although not recorded by Humboldt as medicinal, other species (C. florida, D. virginiana, Q. alba, Q. velutina, X. apiifolia, and Magnolia sp.) were also included in USP and had medical properties known at that time [60].

Known as dogwood, C. florida root barks were described as astringent, tonic, antiseptic (for ulcers, erysipelas, and anthrax), anti-periodic, stimulant, and febrifuge, and when it was used fresh, as emetic. The powdered bark was used as a substitute to Cinchona, indicated for the treatment of intermittent fevers, typhus, and febrile disorders. Twigs used to be chewed to prevent fevers [29,30,31,32]. Cherokee used to chew the barks of C. florida for headache and drink the decoction made of barks for fevers and body aches, and bark poultice was used on sores/ulcers [54], as well as anthelmintic, antidiarrheal, and for hoarseness. Roots were used by Delaware people as tonic, while Rappahannock used the root barks as antidiarrheal, tonic, and to purify the blood; Houma people used barks and roots as febrifuge and antimalarial; decoction of stems and roots were taken for blood chills by Iroquois people [26].

It is reported to Cornus spp. high levels of tannins, mainly in leaves [61], corroborating to astringent property [62]. Millspaugh [30] observed the economic interest for the valuable wood, susceptible to polish, and the use of the young branches without barks as dentifrice, by rubbing them on the teeth, turning them incredibly white; moreover, root barks furnished a red pigment for Native American Indigenous peoples.

Unripe fruits of Diospyros virginiana, known as common or American persimmon, were recorded as astringent by Humboldt, and alongside the barks, were used as styptic, tonic, and antiseptic [29], for internal hemorrhages, anthelmintic [63], and for chronic and subacute catarrhal affections [32]. Cherokee used the plant for its astringent properties, mainly barks infusion for venereal diseases, sore throat and mouth, toothache; treatment of hemorrhoids; syrup for oral thrush, bloody discharge from bowels; the bark was chewed for heartburn [26, 29, 54]. Rappahannock tribe prepared an infusion of the bark to treat trash and sore throat [26]. Rafinesque [29] still indicates the inner barks to treat intermittent fevers. Cherokee, Comanche, and Seminole used the fruit for food [26]. Rappahannock used to prepare a ki