Agueweed

Agueweed
Gentianella quinquefolia

Sometimes you can learn so much from the name of a plant.  I use the names supplied by the USDA Plants Database website - USDA Plants Database.  Most references use the name Stiff Gentian for this plant, but an alternate name is Agueweed, which refers to its medicinal properties.  Look up the word "ague" and you'll find "a fever or shivering fit".

Mrs. Grieve, in her 1931 book, "A Modern Herbal", states that "A tincture is also made from the fresh flowering plant of Gentiana quinqueflora (Five-flowered Gentian) and used in homoeopathy as a tonic and stomachic, and in intermittent fevers.", thus the name Agueweed.

She also uses the name Five-flowered Gentian, which also matches the species name quinqueflora.  The scientific name was given by John Kunkel Small since many of the flowerheads included 5 flowers.  He did most of his collecting in Florida, where they might have mostly had 5 flowers per flowerhead, but I've seen them with all different numbers of flowers.

This flowerhead has way more than 5 flowers.

This is not a very common plant, but can be found in a variety of habitats, from prairies to wet areas, although most if there is limestone close to the surface.