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Wyoming Cooperative Agricultural Pest Survey

Quiz: Noxious Weeds Part 2

Hover mouse over photo for answer

Musk Thistle

Growth Habit: Biennial, winter annual
Leaves: Dark green, light midrib, hairless
Stem: Hairless
Flower: Solitary, terminal, violet to purple
Roots: Fleshy taproot
Seeds: Very viable

Photo by: Steve Dewey, Utah State University, Bugwood.org

 

 

 

 

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Common Burdock

Growth Habit: Biennial
Leaves: Hairy, alternate
Stem: Rough, hairy
Flower: Numerous, clustered, purple
Roots: Large, fleshy taproot
Seeds: Rough, mottled brown

Photo by: Richard Old, XID Services, Inc., Bugwood.org

 

 

 

 

 

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Dyer's Woad

Growth Habit: Biennial or perennial
Leaves: Long, with soft fine hairs
Stem: Woody, upper portion branched
Flower: Small, yellow, 4-petals
Roots: Taproot, up to 5 ft deep
Seeds: Vigorous, in black pods

Photo by: Keith Weller, USDA Agr. Research Service, Bugwood.org

 

 

 

 

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Spiny Plumeless Thistle

Growth Habit: Biennial, sometimes annual
Leaves: Dark green, light midrib, hair on underside
Stem: Winged to flowering heads
Flower: Solitary
Roots: Stout, fleshy taproot
Seeds: Striped lengthwise, slightly curved

Photo by: Loke T. Kok, Virginia Polytechnic Inst. and State University, Bugwood.org

 

 

 

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Houdstongue

Growth Habit: Biennial
Leaves: Velvety, some broad, some narrow
Stem: Heavy, erect
Flower: Dark red, rarely white
Roots: Taproot
Seeds: Flattened,bur-like nutlets

Photo by: Mary Ellen Harte, Bugwood.org

 

 

 

 

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Spotted Knapweed

Growth Habit: Biennial, short lived perennial
Leaves: Long, divided below, fine hairs
Stem: Erect, slender branches, fine hairs
Flower: Solitary, pink, purple, rarely white, Bracts black tipped
Roots: Taproot
Seeds: Notched on one side

Photo by: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

 

 

 

 

 

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Diffuse Knapweed

Growth Habit: Annual or biennial
Leaves: Grayish-green, alternate
Stem: Hairy, erect, single main stem
Flower: Solitary, usually white, sometimes pink
Roots: Elongated taproot
Seeds: Oblong, dark brown

Photo by: Cindy Roche, Bugwood.org

 

 

 

 

 

 

 

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Purple Loosestrife

Growth Habit: Perennial, up to 8 ft tall, moist habitats
Leaves: Simple, lance-shaped, smooth margins 
Stem: Branched, terminating at flower stalks
Flower: Rose-purple, long, vertical racemes
Roots: Large, adapted to aquatic sites

Photo by: John D. Byrd, Mississippi State University, Bugwood.org

 

 

 

 

 

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Saltcedar

Growth Habit: Evergreen shrub, up to 30 ft tall
Leaves: Small, scale like, resemble cedars
Stem: Numerous, slender, highly branched
Flower: Pink to white, five petaled
Roots: Extensive
Seeds: Numerous, easily spread by wind

Photo by: Steve Dewey, Utah State University, Bugwood.org

 

 

 

 

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St. Johnswort

Growth Habit: Perennial, erect, numerous branches
Leaves: Opposite, attached directly to stem, many small perforations in leaves
Stem: Woody at base, rust colored
Flower: Yellow, numerous flat-topped clusters
Roots: Branched and deep
Seeds: Small, shiny black

Photo by: Steve Dewey, Utah State University, Bugwood.org

 

 

 

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Common Tansy

Growth Habit: Perennial, up to 6 ft tall
Leaves: Alternate, deeply divided into narrow leaflets
Stem: Purplish-red in color
Flower: Yellow, button-like, without petals
Roots: Reproduces from roots
Seeds: 5-toothed crown

Photo by: Steve Dewey, Utah State University, Bugwood.org

 

 

 

 

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Russian Olive

Growth Habit: Deciduous perennial shrub
Leaves: Silvery, linear, covered with fine pubescence
Stem: Reddish brown with woody thorns
Flower: Yellow, arranged in clusters
Roots: Taproot
Seeds: Shaped like small olives

Photo by: John M. Randall, The Nature Conservancy, Bugwood.org


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