Noxious Weeds

 

Hooker County Noxious Weed Control Authority

The Director of the Nebraska Department of Agriculture establishes which plants are noxious and the control measures to be used in preventing their spread. The following non-native weeds have been officially designated as noxious in Nebraska:

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SaltcedarSaltcedar (Tamarix ramosissima)

Lifespan: Perennial Shrub or small tree

Origin: Eurasia

Stem: 3 - 20 feet tall

Flowering Dates: April - September

Reproduction: Seeds, root sprouts, buried stems

Saltcedar grows in salt marshes, flood plains, lakeshores and along rivers and streams. A mature saltcedar plant can absorb 200 gallons of water and dense stands may cause springs and small streams to dry up. Saltcedar seed resembles the size and color of pepper and spreads by wind and water. A mature plant can produce as many as 500,000 seeds per year. Branches that are cut and left in a warm moist area will regrow.

Canada Thistle Canada Thistle (Cirsium arvense L. Scop.)

Life Span: Perennial

Stems: 2 to 4 feet tall; hollow; erect; branched above; no leafy wings or spiny margins on upper stems below flowers.

Leaves: Moderate to coarsely lobed, usually wavy with spiny margins. Upper side light to dark green, shiny, hairy to hairless.

Inflorescence: Small 1/2 to 3/4 inch diameter rose purple, sometimes white color, male/female flower on separate plants.

Roots: Extensive vertical and horizontal root system.

Diffuse KnapweedDiffuse Knapweed (Centaurea diffusa Lam.)

Life Span: Biennial or short-lived perennial. Rosette formed during the first year.

Stems: Erect, much branched with rough pubescence. Height 1 to 2-1/2 feet tall. Often branched near or directly above the base.

Leaves: Alternate, deeply divided into narrow segments. Short, or no, leaf stalks. Upper leaves nearly entire or minutely lobed. Gray-green color and covered with fine hair.

Inflorescence: Numerous solitary heads clustered at end of branches, approximately 3/4 inch in diameter. White, pink, or lavender disk flowers. Flower heads surrounded by spiny bracts. Flowers July through September.

Roots: Stout, elongated taproot.

Leafy SpurgeLeafy Spurge (Euphorbia esula L.)

Life Span: Perennial

Stems: 1 to 3 feet tall; thickly clustered; erect; branched at the top; milky white sap.

Leaves: Long and narrow. 1/4 inches wide and 1 to 4 inches long.

Inflorescence: Flower very small, surrounded by showy yellow-green heart-shaped bracts.

Roots: Deep, spreading, brown with numerous pink buds which may produce new shoots or roots.

Musk ThistleMusk Thistle (Carduus nutans L.)

Life Span: Biennial or occasionally an annual. Rosette formed first year.

Stems: Up to 6 feet tall; main stem and major branches are hairless. The stem bearing flower head is covered with fine gray hair with the first few inches below the flower head having no leaves attached.

Leaves: Dark green, prominent light green midrib, usually smooth or hairless on both sides. Deeply lobed with spiny margins up to 20 inches in length.

Inflorescence: Large, solitary 1 to 2-1/2 inches in diameter, usually noding slightly. Deep rose or purple color. Average plant produces 5,000 to 10,000 seeds; some up to 20,000 seeds.

Plumeless ThistlePlumeless Thistle (Carduus acanthoides L.)

Life Span: Biennial or occasionally an annual. Rosette formed in first year.

Stems: 1 to 4 feet tall, leafy to the base of flower heads.

Leaves: Dark green with light midrib. Leaf surface sparsely hairy on top and hairy beneath. Leaves deeply lobed, with narrow spiny margins.

Inflorescence: Solitary in cluster of two to five, blooms 1/2 to 1 inch in diameter, erect and usually not drooping.

Roots: Stout, fleshy, taproot.

Spotted KnapweedSpotted Knapweed (Centaurea maculosa Lam.)

Life Span: Biennial or short-lived perennial. Rosette formed during the first year.

Stems: Slender and erect with numerous wiry branches. Height 1 to 3 feet tall. Roughly hairy.

Leaves: Alternate, deeply divided into narrow segments and covered with short hairs. Leaves much smaller at top of plant and becoming more linear. Seedling leaves form a rosette.

Inflorescence: Numerous terminal and axillary blossoms 3/4 inch in diameter, composed of pink to purple disk flowers. Each head surrounded by leaf-like bract with dark tips and a fringe of bristly hairs. Flowers June through October.

Roots: Stout, elongated taproot.

Purple LoosestrifePurple Loosestrife (Lythrum salicaria L.)

Life Span: Perennial

Stems: Erect, 4-angled, hairless to pubescent, not highly branched, usually from a woody base.

Leaves: Opposite or in whorls; blades simple; lanceolate (long, wide), tip sharply pointed, base rounded or heart-shaped, margins entire, surfaces pubescent; sessile.

Inflorescence: Cymules arranged in spikes, terminal

Roots: Rhizomes, short; taproot

Source: Weeds of Nebraska and the Great Plains, published by the Nebraska Department of Agriculture.

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