Prairie dock (Silphium terebinthinaceum) lines the roadside edge of our Piedmont Prairie Exhibit at the South Carolina Botanical Garden. This plant is towering over the grasses and other prairie plants at about 10 feet tall. At this time of year, mid to late August, it is in full flower. The spray of yellow flowerheads at the head of the bare, tall stems is stunning against the blue summer sky. Each composite flower is about 2 – 2 ½ inches across, and each plant will flower for about a month. Today, when I left work, the flowers were covered in eastern swallowtail butterflies dancing in the breeze. Other pollinators are also attracted to the blooms, which are held high above the competing vegetation. Long-tongued bees, many small bees, hoverflies, and hummingbirds are all regular visitors. Goldfinches and probably other small birds and mammals are attracted to the seeds.
The spray of Prairie Dock yellow flowerheads is stunning against the blue summer sky.
Sue Watts, ©2023, SC Botanical Gardens, Clemson University
Each Prairie Dock flower is about 2 – 2 ½ inches across.
Sue Watts, ©2023, SC Botanical Gardens, Clemson University
Butterflies are attracted to the blooms, which are held high above the competing vegetation.
Sue Watts, ©2023, SC Botanical Gardens, Clemson University
Goldfinches and other small birds and mammals are attracted to Prairie Dock seeds.
Sue Watts, ©2023, SC Botanical Gardens, Clemson University
This native plant is distributed throughout eastern North America, including South Carolina. Prairie dock is a survivor from the era when prairie dominated the Piedmont. We know from the early explorers that the landscape at that time was covered in tall grasslands grazed by bison and that they were burned regularly by the indigenous population. This plant is well adapted to harsh prairie conditions. The large basal leaves are oriented in a north-south direction, so the blades of the leaves face east-west. Not only does this increase the rate of photosynthesis, but it also reduces the amount of water vapor loss via transpiration. If you touch these leaves in the heat of summer, they remain cool to the touch. The roots of prairie dock are deep, up to 12 feet deep, enabling it to reach the water table.
This plant’s scientific name, as with many plants, tells a tale. The Latin “Silphium” relates it to a prized resin-bearing plant of North Africa. The specific epithet, terebinthinaceum, means like turpentine, referencing the resin found in the stem. Reputedly, this resin was used as chewing gum and has a carroty-pine flavor (reportedly, this plant is toxic, so don’t try this).
This is a plant best grown from seed; the long taproot makes transplanting a challenge. However, starts are available in the nursery trade. Plant prairie dock in full sun with good drainage and in a space you have selected carefully. Reports indicate that it can live for a century or even more!
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