Rattlesnakemaster, or button eryngo, is a member of the Parsley (Apiaceae) family. It is a stout-stemmed, hairless plant growing up to 4 feet tall, with a blue-green cast in summer. Leaves resemble Yucca leaves and are long and strap-shaped with small, needlelike teeth scattered along the edges. Flowers are in several individually stalked heads at the top of the plant, forming an open, flattened cluster of dense ball-like flower heads. The heads are covered with many tiny, white, 5-petaled flowers and have pointed whitish bracts. Each flower has 2 protruding threadlike styles.
Rattlesnakemaster blooms in summer and is frequent in prairies and open, rocky savannas through most of the tallgrass region north and west to Iowa and southern Minnesota, becoming more local east of Illinois.
Native Americans used this plant for rattlesnake bite (hence the common name) and for reproductive disorders.