Up to three hundred times as sweet as sugar, the calorie-free steviol glycosides in stevia have been known and exploited for at least 1500 years.
The Guaraní of South America (centred around modern-day Paraguay) are the first known human users of stevia, using it to sweeten teas, as a medicine, and as a treat. Their name for it is ka’a he’ê, meaning “sweet herb”. The species was scientifically described in 1899, while the glycoside compounds were isolated and identified in 1931. In the 1970s, stevia became commercially used as a sweetener in Japan, but its adoption in North America and Europe has taken somewhat longer (see, e.g., this March 2014 discussion from the Harvard Medical School: “More about stevia, a non-approved sweetener“). Regulations continue to loosen as studies are completed, and stevia (or at least its derivative (and presumably patented / trademarked) compounds) is now found in many reduced-calorie / no-calorie foods and beverages.
Estimates for the global market value in 2014 of stevia were in the range of 336 million USD, with forecast for a 550+ million USD value in 2024. This could have been a significant part of Paraguay’s economy (GDP of 27.5 billion USD) had production remained within the country, but the largest global producer of stevia is China. Efforts are being made to develop it as a crop in the USA.
Stevia is a member of the sunflower family. I didn’t get a chance to see this small shrub in flower (likely too short of a growing season here), but an image of the inflorescence is here: Stevia rebaudiana inflorescence, via Wikimedia Commons. I will admit to sampling a leaf from today’s plant, which I enjoyed more than the taste of products sweetened by its extracts.