As distinctive as the tremendous wands of flowers which mark the presence of rosin weed are the tall stalks of the prairie dock which rise above great spade-shaped leaves. The leaves themselves are individuals; there is nothing else like them in prairie, swamp, or forest.

Prairie Dock.

Silphium terebinthinaceum Jacq.

July - August Prairie roadsides.

Prairie dock leaves come up in spring and stand without flower stalks or further growth until August. The leaves are a foot or more long, on stalks of shorter length, and are thick, resinous, spade-shaped, and coarsely toothed. These leaves, like those of other Silphiums and plants which, like these, live in hot, open sunshine and wind, are coated with a rough waxy layer and are constructed in such a manner that moisture is not easily evaporated from them. In the hottest weather the leaves do not wilt. They are erect above the ground and thus present only their thin edges to the sun, not the broad faces of the leaves as the water lilies and Lotuses do.

In August, from among the clusters of leaves, there spring tall, smooth stalks, at the top of which are less than a dozen smooth round buds. These open as small sunflowers, very much like those of rosin weed, but smaller and more delicate. High above the large leaves, these grace-ful stalks seem to have no connection with the leaves or roots. Up in the sunshine and against the prairie sky, the flowers of prairie dock wave in the wind, bloom and go. The resin in the leaves and stems has an odor suggestive of turpentine, hence the Latin name "terebinthinaceum".