(Button eryngo, Button Snakeroot). Rattlesnake-master is an erect perennial reaching to 5 feet high, growing from a small bundle of roots and a taproot into a stout stem, unbranched up to the inflorescence. Leaves are alternate, long, stiff, narrow to a sharp point and have spiny edges. Most leaves of any size are near the base of the stem. These can grow to 3 feet long. Upper leaves are small. A characteristic of the leaf is the parallel vein structure. The leaf clasps or wraps around the stem with a long sheath. Stems and leaves are hairless, bluish or grayish green. The inflorescence is long stalked with terminal branched clusters (cymes) that are usually 1" round balls covered with tiny 5-part white to purplish flowers. The white stamens have brown anthers for contrast. These heads are contracted umbels. Each flower has prickly bracts and the entire ball has at its base a small rosette of small leaves. These flower clusters can also spring from an upper leaf axil. In bloom, the flowers have a honey-like scent. The flowers mature to a scaly dry fruit that splits into 2 seeds. An unusual plant for its strap like leaves and spiny margins, resembling the yucca of the southwest, but a true prairie species of the dry-mesic to wet-mesic prairies. It is easy to grown in the home landscape in well drained soils with full sun.

Names: The genus name Eryngium is Greek meaning "prickly plant" and the species name refers to the yucca-like leaves. A different plant of this genus, Eryngium aquaticum L., is also known as Rattlesnake-master, and so termed by USDA, who refers to this species as Button eryngo. Eryngium aquaticum is native to the U.S. east and gulf coasts, but not inland. Some references will confuse the two. Medicinal qualities are attributed to members of the Eryngium genus and those referring to Rattlesnake-master are probably alluding to the latter species.