Perennial grasses suppress weeds

Weeds often thrive in noncrop areas such as levees, roadsides, and field borders, but they can be suppressed by planting native grasses and treating the area with herbicides, according to an article in the January–March 2010 issue of Invasive Plant Science and Management.

The article, “Integrating Herbicide Use and Perennial Grass Revegetation to Suppress Weeds in Noncrop Areas,” examines perennial grass revegetation efforts from 2004 to 2007 at three sites in Northern California. Authors Rob G. Wilson, Steve B. Orloff, Donald L. Lancaster, Donald W. Kirby, and Harry L. Carlson evaluate how weedy noncrop areas can be managed by establishing a stable plant community.

“Rangeland research suggests revegetation of disturbed land can greatly improve long-term weed suppression,” according to the authors. “The interaction between weed control and individual grass species for perennial grass cover was significant at all sites all three years, suggesting weed control influenced the establishment and vigor of perennial grass species.”

Herbicides were used for the first two years of the study but not the third, so the researchers were able to observe the perennial grasses’ ability to suppress weeds. At each site, herbicides were not applied to one block, where the perennial grass species did not thrive. Also, in herbicide-treated plots where grass seed was not planted, weed cover was more extensive.

“These results suggest that weed control can be essential for perennial grass revegetation in weedy noncrop areas,” according to the authors.

Although the herbicides used in the study were selected to minimize their effects on the perennial grasses, one — imazapic — caused significant injury during the seeding year. This resulted in “a trade-off between weed control and nontarget plant injury that land managers should consider when using herbicides,” the researchers say. “Herbicide treatments that provided wide-spectrum weed control with soil residual activity resulted in the best weed control one and two years after seeding.”

Of the 15 perennial grasses planted during the study, the researchers identified 4 that provided the best weed suppression: crested, western, tall, and bluebunch wheatgrass.

The full text of the article, “Integrating Herbicide Use and Perennial Grass Revegetation to Suppress Weeds in Noncrop Areas,” Invasive Plant Science and Management Vol. 3, Issue 1, March 2010, is available at

TAGS: Management
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