Flower:

Whitish green globe-like flowerheads, ½ to ¾ inch wide, are arrayed in an orbital cluster at the end of a tall, smooth stalk. Each flower head is composed of numerous small flowers with 5 white petals, notched at the tip, 2 long white styles, and 5 white stamens with greenish to brown tips. Surrounding each flower are prickly floral bracts. At the base of the flower head is a whorl of leafy bracts, lance-like and prickly. A plant has a few to many clusters from the leaf axils and on branching stems in the upper part of the plant.

Leaves and stem:

Leaves are mostly basal, long and sword-like with parallel veins and tapering to a sharp point, up to 2½ feet long and only 1 inch wide with a few smaller leaves ascending the stem. Stem leaves are stiff, clasp the stem and typically wrap around it. Leaf surfaces are waxy, the edges either smooth or commonly with widely spaced, fine spiny teeth. Stems are hairless, blue-green, waxy, and ridged.

Fruit:

The flower heads turn purplish in the fall and eventually dry to a dark brown. 

Seed is dark brown, 3-sided, just under 1/8 inch long, the layered remains of the floral bracts attached at the top on 2 sides with the third side smooth and flat.

Notes:

To any sense of observation, this one is a no-brainer as Rattlesnake Master is a unique plant—at first encounter it is startlingly different than most native plant forms. It also makes an excellent garden specimen as a durable perennial in most soil types with adequate sun. According to the DNR, while Rattlesnake Master does grow in a variety of habitats, in Minnesota—the northern edge of its natural range—it has limited itself to open prairies, which have all but disappeared. It was designated a Special Concern species in 1994.