Crop Watch, June 9, 2006: Controlling hoary vervain in pasture<p>

University of Nebraska-Lincoln Extension, Institute of Agriculture and Natural Resources

Controlling hoary vervain in pasture

(Photo by Jennifer Anderson @ USDA-NRCS PLANTS Database)

Hoary vervain (Verbena stricta), also known as wooly verbena or tall vervain, is a common native weed in northeast Nebraska in over-grazed rangeland, prairies and disturbed sites in all soil types.

Plant description

Several other types of vervain in Nebraska (prostrate, white, and blue) have similar growth forms and habits as hoary vervain. Hoary vervain is a perennial forb from the vervain family (Verbenaceae) that reproduces by seeds. The taproot (perennial structure) produces individual erect plants. Its stem is nearly round, simple or branched above and can be up to 5 feet tall, covered with soft white hairs. Leaves are opposite and leaf blades are ovate with many teeth. The lower surface of a leaf is pubescent with highly visible veins. Like many other plant species, the overall growth and development depends on the amount and timing of rainfall. In Nebraska hoary vervain can flower from May to September, with blue or purple flowers positioned on the top of the main stem and branches and producing a two-seeded fruit.

Hoary vervain provides forage for deer and its seeds are an important food source for small mammals and upland birds. Native Americans also made a tea from the leaves to treat stomachaches. Hoary vervain has no value to livestock because of its low palatability.

Control

This weed can be controlled by various means.

Mowing. Mowing the plants when they are 3-5 inches tall can reduce vervain population considerably for the season. Mowing can be done one or two times per season depending on the amount of rainfall during the season. One mowing in mid June can be effective, providing more than 75% control, if the season is dry, due to lack of moisture available for weed regrowth. If the season is wet, an additional mowing is needed in July or August.

Chemical. Herbicides also can provide effective season-long control. Herbicide application should be conducted when vervain plants are 3-5 inches tall, which is usually in early June. Effective herbicides, their rates and cost per acre include: Salvo (12 oz/ac, $4), Grazon P+D (32 oz/ac, $8), Weedmaster (32oz/ac, $6), Ally (0.25oz/ac, $8), and Vista (22 oz/ac, $8).

Stevan Knezevic
Extension Integrated Weed Specialist
Haskell Ag Lab, Northeast REC

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Copyright 2006 by the University of Nebraska Board of Regents. All rights reserved.

Published by University of Nebraska-Lincoln Extension in the Institute of Agriculture and Natural Resources Cooperating with the counties and the U.S. Department of Agriculture.

The University of Nebraska-Lincoln does not discriminate on the basis of gender, age, disability, race, color, religion, marital status, veteran's status, national or ethnic origin, or sexual orientation.




Copyright 2006 by the University of Nebraska Board of Regents. All rights reserved.

Published by University of Nebraska-Lincoln Extension in the Institute of Agriculture and Natural Resources Cooperating with the counties and the U.S. Department of Agriculture.

The University of Nebraska-Lincoln does not discriminate on the basis of gender, age, disability, race, color, religion, marital status, veteran's status, national or ethnic origin, or sexual orientation.