Moving upriver on the Arkansas River from Fort Smith on July 8, 1819, Thomas Nuttall noted: “On Sambo Island [=San Bois Island, near the mouth of Little San Bois Creek – San Bois means without trees]…we stopped to dine; and here on a bar of gravel I found a new species of the Mexican genus Stevia…To the taste it was quite as bitter as many of the Eupatoria” (pg. 185-186).
Years ago when I first read this passage I had never heard of Stevia, and so this comment on a new species didn’t connect with me much. Now, of course, we all have heard of Stevia, and multiple brands are on the shelf at Walmart.
Other taxonomists subsequently decided that Nuttall’s new plant, while related to the “Mexican” Stevias, belonged in a different genus – Palafoxia. Today it is known as Palafoxia callosa (Nutt.) T. and G. The Nutt. in parentheses memorializes that Nuttall was the first to describe the species – from an island in the Arkansas River in what’s now eastern Oklahoma.
Stevia rebaudiana is the source of the sugar substitute, and native to parts of Brazil and Paraguay. Common names include candyleaf and and sugarleaf. Closer to home the Texas candyleaf, which grows in the Big Bend area of Texas and Mexico, is Stevia ovata var. texana.
So the bitter taste of Palafoxia described by Nuttall stands in contrast to the sweet of the Stevias.
The genera Stevia and Palafoxia are both in the Sunflower Family (Asteraceae). The Flora of Oklahoma lists four species of Palafoxia, and none of Stevia. The Arkansas Atlas lists only Palafoxia callosa, and collections are all from the northern tier of Ozark counties (note: an area of limestone soils). The Flora of North America lists seven Stevia species, all in western and southern US, and points south. It lists 10 species of Palafoxia in the US and Mexico.
The keys in the Flora of Oklahoma distinguishes P. callosa from a second species, P. rosea, in part part by placing the former on calcareous (i.e., limestone) soils and the latter on sandy soils.
Makes me wonder a bit about the gravel bar where Nuttall found it. Was the gravel on San Bois Island derived from “Ozark” gravel, brought down by the Illinois and other rivers entering the Arkansas from the north?