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Tennessee Native Plant Society
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Native Plant of the Month
February, 2011
Prairie Dock
Silphium terebinthinaceum
Very large basal leaves are spade shaped with toothed margins from which sprouts inflorescences that
are up to 5 feet tall. The flowers are reminiscent of sunflowers and are 3 inches across. Silphiums differ
from sunflowers (Helianthus) in that the disk flowers of Silphium are sterile and the ray flowers are fertile. In
Helianthus, the disk flowers are fertile and the ray flowers are sterile. These plants are found in dry rocky
barrens across Tennessee flowering in fall.
Silphium terebinthinaceum
Very large basal leaves are spade shaped with toothed margins from which sprouts inflorescences that
are up to 5 feet tall. The flowers are reminiscent of sunflowers and are 3 inches across. Silphiums differ
from sunflowers (Helianthus) in that the disk flowers of Silphium are sterile and the ray flowers are fertile. In
Helianthus, the disk flowers are fertile and the ray flowers are sterile. These plants are found in dry rocky
barrens across Tennessee flowering in fall.
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