Grotesque and somewhat over-elaborate as a flower, Hill's thistle in June sets its large flowers above ten-to-twenty-inch stalks on the sunshiny prairie. The plant is low and stout and finely downy, as well as extremely prickly on the twisted and deeply cut and spiny leaves. It always appears as if this thistle plant were buried in the ground with only the last half foot or so thrusting through the tough prairie sod. But this is a characteristic of the Hill's thistle and the closely related bull thistle.
Cirsium hillii (Canby) Fern.
Summer Roadsides, prairies.
The flower of Hill's thistle is a large, globular head of bright rose-purple or pink, or rarely white, florets bursting from the prickly, orderly receptacle with its individual fine prickles standing out at intervals. The flower is a composite mass of long purple florets from which thrust the powdery, cream-white stamens and the long, thin pistils. When the thistle is fertilized, usually by butterflies, the flower becomes a mass of downy fluff, at the base of which are the seeds. When goldfinches come to eat the seeds and use the silk for nest-building purposes, the released silks often float away on the wind.
The low, compact Hill's thistle is found on open prairie land along the highways and occasionally in prairie pasture land. The very Large flowers are instantly noticed even by passing motorists, and by botanists seeking typical plants of the Illinois prairie.
The common bull thistle (Cirsium vulgare) is a biennial plant, three to five feet tall, which has come to us from Europe and has become established in pastures and old fields throughout the state. Its leaves are green on both sides, which serves to distinguish it from the field thistle, which has leaves white beneath.