On Nature column: Prairie dock a tall, distinctive wildflower

Nov 23, 2023

For The Herald Bulletin

Prairie dock is closely related to the sunflower.

One of the tallest of the most distinctive species of wildflowers native to prairies and other sunny habitats in Indiana is prairie dock (Silphium terebinthinaceum).

This member of the composite family has large spade-shaped basal leaves with a rough sandpaper-like texture. Yellow daisy-like flowers develop on tall stalks from late July through early September.

The large seeds that mature in the fall show their close relationship to sunflowers since the edible kernel is nearly identical to a sunflower kernel in size, taste, and shape.

The range of prairie dock encompasses the eastern tallgrass prairie region from Ohio west to Missouri and from Michigan south to the Tennessee Valley. Although it is most abundant on loamy prairies, it adapts to a wide variety of wet to dry sunny habitats.

In east central Indiana, it is mostly found in fens, but also spreads along railroad right-of-ways and roadsides. In the southern portions of its range including southern Indiana, it grows on limestone glades, which are areas of thin dry soils over limestone bedrock.

It was undoubtedly abundant in the black soil prairies of northwest Indiana where the few remnant prairies are often punctuated by its distinctive foliage.

The large basal leaves of prairie dock can reach up to three feet in height, including the stem, and a foot in width. The leaves have cordate bases and coarse teeth along their margins.

Despite their rough texture, they are eagerly devoured by livestock and soon disappear with continuous grazing. In the fall they crinkle up like crumpled brown paper sacks when the plants go dormant.

Prairie dock is a long-lived perennial that develops a thick taproot that can be several inches in diameter and reach several feet into the ground when they grow in well-drained deep soils.

The taproot is more sprawling when they grow in wet situations or on the thin soils of glades. They often take 3-5 years to flower from seed while they develop this large taproot.

The flowers peak in August and continue into September. They are perched atop smooth branched stalks up to 10 feet in height. Each flower is around 2 inches across with showy yellow ray flowers surrounding a central disc that contains the fertile florets.

The female flowers are found in a ring around the disk resulting in a ring of seeds when they ripen in late September and early October.

Prairie dock attracts a variety of pollinating bees including bumblebees, miner bees and non-native honeybees. Butterflies and hummingbirds also occasionally visit the flowers for nectar.

The large edible seeds are consumed by goldfinches and are also likely eaten by rodents such as mice, chipmunks and ground squirrels.

Prairie dock is easily grown in full sun in a variety of conditions, making a unique conversation piece in the perennial garden.

Kevin Tungesvick is a lifelong resident of Madison County. An avid naturalist and self-taught botanist, Kevin is author of a floral inventory of Mounds State Park. He is a founding director of Heart of the River Coalition.

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