South Dakota Department of Agriculture
For Immediate Release: Friday, July 5, 2002
Contact: Ron Moehring, (605) 773-3796 or 1-800-228-5254

Watch out for New Weed Infestations 

Pierre, S.D -- The current drought conditions have created a demand for forage across the state and this means some marginal areas are being put up for hay.  Some of these marginal areas may be infested with noxious weeds.  “Anyone purchasing hay should closely monitor storage areas, feed lots, and pastures for new weed infestations,” said State Weed and Pest Supervisor Ron Moehring.  Even hay that appears clean may harbor Canada thistle, leafy spurge, or other noxious weed seeds. 

Landowners need to know what noxious weeds look like and watch their lands closely for new outbreaks. “The cost of not treating a new outbreak is years of fighting the weed in the future,” said Moehring.  

Leafy spurge stands between 2 and 3 feet tall with greenish yellow flowers and narrow, dark green leaves 1 to 4 inches long. The entire plant contains a milky sap.   

Canada thistle flowers are about ¾-inch in diameter and usually lavender colored but may be pink or white.  The stems are grooved and can be up to 5 feet tall and branching at the top.  The leaves are medium green, tipped with spines and have a crinkled margin.

Russian knapweed has small lavender to white thistle-like flowers approximately ½-inch in diameter.  The stems are 2 to 3 feet tall, highly branched and covered with short white hairs. Leaves on the upper stem are narrow and not lobed. Leaves at the base of the plant are large, covered with short white hairs and deeply lobed with a dandelion-like appearance. 

Hoary cress has numerous small, 4-petaled, white flowers in a flat-topped cluster at the end of each branch.  Stems are 1 to 2 feet tall, branched near the top and covered with short, whitish hairs.  The leaves are alternately arranged, blue-green in color, oblong shaped, irregularly toothed and ½- to 3 inches long.  The lower leaves are stalked while the upper leaves have 2 lobes clasping the stem.  

Purple loosestrife flowers are purple-magenta with five to six petals arranged in long spikes.  The stems are woody, four- to six-sided and stand up to 8 feet tall.  The leaves are opposite with linear smooth margins and no petiole. 

Perennial sow thistle flowers are yellow-orange and about 1-½ inches in length. The stems are smooth, 3 to 7 feet tall, and contain a milky juice.  The leaves are dandelion shaped and 4 to 8 inches long. 

For more information on these and other noxious weeds or to get a noxious weed identification guide, contact your county weed and pest supervisor, county extension educator, the South Dakota Department of Agriculture or check our web site at: http://www.state.sd.us/doa/das/noxious.htm#weed.

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