LaBarque Creek Conservation Area is one of the finest outdoor destinations in Jefferson County.
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Scientific Name
Silphium terebinthinaceum
Family
Asteraceae (daisies, sunflowers)
Description
Prairie dock is a tall perennial herb with woody taproots. The flower stalk is very slender, with reduced stem leaves. The foliage has a pleasant scent, somewhat like turpentine.
The flowerheads are one to few in an open inflorescence on a long stem; yellow, with 15–21 rays.
Blooms July–October.
The leaves are almost all basal, very large, to 16 inches long, heart- or spade-shaped, with coarse teeth, on a long petiole (leaf stem), thick, leathery, and rough like sandpaper. The leaves develop all summer and are present at flowering time.
Similar species: There are 6 Silphium species recorded for Missouri. Of these, prairie dock, starry rosinweed (S. asteriscus), rosinweed (S. integrifolium), compass plant (S. laciniatum), and cup plant (S. perfoliatum) are relatively common. Prairie dock is identified by its large, basal, unlobed leaves with only small, bractlike leaves on the stem.
Size
Height: to 10 feet.
Where To Find
Scattered, mostly in the Ozark and Ozark Border Divisions, in central and northeastern Missouri.
Habitat and Conservation
Occurs in glades, upland or rocky prairies, tops of bluffs, savannas, openings of dry upland forests, and rarely banks of streams; also old fields, railroads, and roadsides. Look for it in areas with limestone or dolomite rock.
Status
Native Missouri wildflower.
Human Connections
Prairie dock is a tough, showy native flower for the back of a garden. It can also be grown as a specimen plant in a prominent place.
The species name means “with turpentine” and refers to the rosin, which gives this plant a pleasant, spicy scent.
Although the resinous sap has an odor somewhat like turpentine, grazing animals find this plant palatable.
As with other rosinweeds, the gummy sap that this species exudes was used by Native Americans and pioneers as a kind of chewing gum.
Ecosystem Connections
Birds, including goldfinches, eat the seeds.
Many insects visit and pollinate the flowers. If you inspect a rosinweed plant closely, you will find that many insects live, hunt, eat, and mate among the leaves and flowers. Also, the larvae of some wasps grow with in the stems, forming galls.
Like its relative compass plant, the leaves of prairie dock often are oriented north and south, maximizing morning and afternoon sun for photosynthesis and minimizing water loss from midday heat. This is an adaptation for life in hot, dry prairie and glade habitats.
Prairie dock and other rosinweeds are in their own genus, Silphium, and not in the genus Helianthus (sunflowers). Yet some of them look much alike. How can you tell the difference? It has to do with which parts of the compound flowerheads produce seeds. The disk (center) florets in rosinweeds are essentially staminate (male) and therefore don’t create seeds, just pollen; but the disk florets in sunflowers, as most of us know, create seeds. Meanwhile, the petal-like ray florets in rosinweeds are pistillate (female) and turn into seeds, while those in sunflowers are sterile.
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Media Gallery
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Caption
Of Missouri's six species of rosinweeds, prairie dock is identified by its large, basal, unlobed leaves; there are only small, bractlike leaves on the stem.
Credit
Julianna Schroeder
Right to Use
Photo by Julianna Schroeder, courtesy Missouri Department of Conservation
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Caption
Prairie dock's basal cluster of large, unlobed leaves, combined with its very tall, leafless stalks, helps ID this plant.
Credit
Julianna Schroeder
Right to Use
Use of this image is restricted to MDC only
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Caption
Prairie dock is common in areas with limestone or dolomite rock. It can be a tough, showy native flower for the back of a garden.
Credit
Julianna Schroeder
Right to Use
Use of this image is restricted to MDC only
Image
Caption
Of Missouri’s six rosinweeds, prairie dock is identified by its large, leathery, unlobed leaves, which are nearly all in a basal whorl.
Credit
Allen Bridgman, South Carolina Department of Natural Resources, Bugwood.org
Right to Use
Use of this image is restricted to MDC only
Image
Caption
Prairie dock, like other Missouri rosinweeds, has yellow, sunflower-like flowerheads.
Credit
Vern Wilkins, Indiana University, Bugwood.org
Right to Use
Use of this image is restricted to MDC only
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Prairie dock
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Where to See Species
Clifty Creek Conservation Area and Clifty Creek Natural Area are adjacent to one another and combined offer the public 486 acres in Maries County to enjoy.
This 40-acre native prairie remnant is owned by the Missouri Prairie Foundation and is jointly managed with the Conservation Department.
Long Ridge Conservation Area is located in Franklin County, near Sullivan. The area includes nine miles of developed, seasonal multi-use trails and five parking areas.
About Wildflowers, Grasses and Other Nonwoody Plants in Missouri
A very simple way of thinking about the green world is to divide the vascular plants into two groups: woody and nonwoody (or herbaceous). But this is an artificial division; many plant families include some species that are woody and some that are not. The diversity of nonwoody vascular plants is staggering! Think of all the ferns, grasses, sedges, lilies, peas, sunflowers, nightshades, milkweeds, mustards, mints, and mallows — weeds and wildflowers — and many more!