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Published on: Aug. 2, 2000

Last revision: Nov. 5, 2010

labor the root was still enlarging, like a great vertical sweet-potato. As far as I know, that Silphium root went clear through to bedrock.

I got no Silphium, but I learned by what elaborate underground stratagems it contrives to weather the prairie drouths." In fact, the roots of compass plant, rosinweed, starry rosinweed and prairie dock can attain depths of 10 to 15 feet.

Perhaps no other plants in Missouri are as easily recognizable and as widespread as Silphium species. And, with their preference for various natural communities, their presence gives a dramatic flair to our prairies, glades, wetlands and ditches.

We often remember individual trees we have seen along the road or on a favorite hike, and even revisit them year after year. Plants like the species of Silphium are perhaps even more impressive than trees. Left undisturbed, they can attain a height of 10 feet every year, die back and begin the growth cycle again, for years and years.

Prairie dock - Silphium terebinthinaceum

"With turpentine," is the translation for the Greek name, terebinthinaceum, given to prairie dock for its resinous sap. A common sight on Ozark limestone glades, bald knobs and some prairies, the large toothed leaves of prairie dock stand upright like giant spade-shaped pieces of green sandpaper.

Prairie dock flowers are as striking as the leaves. The bright yellow flowers top slender stalks that rise up to 10 feet above the leaves in mid to late summer. Strangely enough, prairie dock prefers prairies in Iowa, Illinois and Indiana, but in Missouri it favors glades and rocky roadsides.

Cup plant or carpenter's weed - Silphium perfoliatum

Cup plant leaves are paired on opposite sides of the stem, and the pairs are arranged at right angles to each other along the stem. The scientific name of cup plant, perfoliatum, means "through the leaf," referring to the stem that appears to pierce the leaves. These stem-enclasping leaves are described as perfoliate and form a cup that can hold water. Whether this ability is advantageous to the plant is unknown, but small birds and insects have been known to drink from these cups.

As if the leaves weren't enough to make the plant striking, cup plant has square stems, which prompted the other common name of the plant, carpenter's weed. The

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