Rattlesnake Master also known as Button Eryngo, Erygium yuccifolium, is a perennial wildflower. Scattered along the stiff, upright stem of this plant are blue-green, yucca-like, parallel-veined leaves. Smooth, rigid stem bearing thistle-like flower heads made up of small greenish-white florets are mingled with pointed bracts. This is a unique plant adapted for drained, dry soils and full sun.