Overview

Comprehensive Description

Description

This plant has a vase-like rosette of large basal leaves that are spade-shaped (cordate). Each leaf has a thick sandpapery texture, particularly on the underside, and is up to 18" long and 12" wide. On young leaves, the upper surface is relatively hairless and shiny, while older leaves become dull and rough. The lower surface is light green and pubescent. The leaf margins are coarsely serrated or dentate. The petioles are about 6" long, rather narrow and wiry, and light green or brown. The overall appearance is similar to a rhubarb plant, except the petioles are more slender. A naked flowering stalk emerges from the base of the plant, ranging in height from 3' to 10' in height. This stalk is green or red, and largely hairless. The upper part of the stalk divides gracefully into a panicle of yellow composite flowers and spherical green buds. Each compound flower is about 2-3" across, and consists of 15-30 ray florets with rather pointed tips surrounding numerous disk florets. There is no noticeable floral scent. The blooming period usually occurs from late summer to early fall, and lasts about a month for an individual plant. Prairie Dock usually blooms later than other Silphium spp. It has a stout taproot that can penetrate the soil to about 12' deep, and may form offsets only a short distance away from the mother plant. The rather light, flattened achenes can be carried several feet by the wind; they are without tufts of hair.
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Source: Illinois Wildflowers

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Comments

This is a typical plant of mesic black soil prairies that competes successfully with tall prairie grasses. It has an impressive and unusual appearance, like something out of the Stone Age when Columbian mastodons and other megafauna inhabited the prairies of North America. Return
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Source: Illinois Wildflowers

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Distribution

Range and Habitat in Illinois

Prairie Dock occurs in most of Illinois, except for a few counties in the south and NW (see Distribution Map). It is a common plant. Habitats include moist to dry black soil prairies, gravel prairies, shrub prairies, hill prairies, savannas, seeps, limestone glades, and prairie remnants along roadsides and railroads. The exceptional height of the flowering stalk is probably useful in keeping the flowers above the taller grasses, such as Andropogon gerardii (Big Bluestem). Recovery from occasional wildfires is very good. Faunal Associations
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Localities documented in Tropicos sources

Silphium terebinthinaceum Jacq.:
Canada (North America)
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.
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National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

United States

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

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Physical Description

Morphology

Description

Plants scapiform, (40–)100–250+ cm; taprooted. Stems terete, glabrous. Leaves: basal persistent, petiolate; cauline alternate, petiolate or sessile; blades cordate, deltate, lanceolate, ovate, or sagittate, 3–40 × 1–40 cm, sometimes (proximal) pinnately lobed, bases attenuate, cordate, hastate, round, or truncate, ultimate margins coarsely toothed or entire, apices acuminate, acute, or obtuse, faces glabrous or scabrous. Phyllaries 23–33 in 2–3 series, outer appressed, apices obtuse to acute, abaxial faces glabrous. Ray florets 17–29; corollas yellow. Disc florets 120–140; corollas yellow. Cypselae 7–13 × 4–10 mm; pappi 0–1 mm.
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Ecology

Habitat

Range and Habitat in Illinois

Prairie Dock occurs in most of Illinois, except for a few counties in the south and NW (see Distribution Map). It is a common plant. Habitats include moist to dry black soil prairies, gravel prairies, shrub prairies, hill prairies, savannas, seeps, limestone glades, and prairie remnants along roadsides and railroads. The exceptional height of the flowering stalk is probably useful in keeping the flowers above the taller grasses, such as Andropogon gerardii (Big Bluestem). Recovery from occasional wildfires is very good. Faunal Associations
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Associations

Flower-Visiting Insects and Birds of Prairie Dock in Illinois

Silphium terebinthinaceum (Prairie Dock)
(Bees collect pollen or suck nectar, hummingbirds and other insects suck nectar; most observations are Robertson, otherwise they are from Petersen and Hilty as indicated below)

Birds
Trochilidae: Archilochus colubris sn

Bees (long-tongued)
Apidae (Apinae): Apis mellifera sn cp fq; Apidae (Bombini): Bombus bimaculatus (Pt), Bombus impatiens sn cp, Bombus pensylvanica sn; Anthophoridae (Ceratinini): Ceratina dupla dupla sn cp; Anthophoridae (Eucerini): Melissodes agilis (Pt), Melissodes coloradensis sn, Svastra obliqua obliqua sn cp; Megachilidae (Megachilini): Megachile brevis brevis sn

Bees (short-tongued)
Halictidae (Halictinae): Agapostemon sericea sn, Halictus ligatus sn cp fq, Halictus rubicunda (Pt)

Wasps
Sphecidae (Sphecinae): Ammophila procera sn

Flies
Bombyliidae: Sparnopolius confusus sn, Systoechus vulgaris sn

Butterflies
Nymphalidae: Danaus plexippus sn (H)

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Silphium terebinthinaceum

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 4
Species With Barcodes: 1
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Source: Barcode of Life Data Systems (BOLD)

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Conservation

Conservation Status

National NatureServe Conservation Status

Canada

Rounded National Status Rank: N1 - Critically Imperiled

United States

Rounded National Status Rank: NNR - Unranked

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NatureServe Conservation Status

Rounded Global Status Rank: G4 - Apparently Secure

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Threats

Comments: Loss of natural habitat and conversion of natural forest to commercial forests are low-level threats to outlying populations in the Piedmont (Southern Appalachian Species Viability Project 2002).

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Relevance to Humans and Ecosystems

Benefits

Cultivation

The preference is full sun, a deep loamy soil, and moist to slightly dry conditions. Rocky or gravelly soil is tolerated. Drought tolerance is very good. Prairie Dock is rather slow to develop, but very reliable and nearly indestructible when mature. Patches of brown may develop when the leaves are damaged by drought, windstorms, or passing animals. It is a long-lived plant.
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© John Hilty

Source: Illinois Wildflowers

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