Foster Creek Conservation District
Foster Creek Conservation District

Fighting Aggressive Weeds with Native Plants

By Ryan Lefler

Wild blue flax with a sleepy beetle

As the weather gets warmer, everyone is gearing up to farm and garden. However, we also must prepare to combat the seasonal onslaught of weeds. The many kinds of aggressive invasive plants that come back year after year can leave producers, land managers, and homeowners feeling exhausted. Besides chemical, mechanical, and biological controls, what other tools can a person use to stop the annual tide of persistent weeds? One option we have is native plants.


Plants native to the area are adapted to the unique climate and soils present. Once a healthy community is established, it helps repels invasive plants by taking up the space and available sunlight weeds need to grow. A 2015 study in Nature, a scientific journal, found that when two native forbs were planted in plots where invasive morning glory was cleared, regrowth of the invasive was up to 11 times less. Weeds love bare and/or disturbed ground, so keep yours covered.

 

Weeds on bare soil

Most of us who deal with persistent patches of weeds are used to spraying or discing, only to find that a new crop has sprouted a month later. This is because an underground seed bank lurks below the surface, remaining viable for decades. By clearing out the previous population, we have created perfect conditions for the next generation of weeds. If you have just treated a weedy area, force the seed bank to stay dormant by sowing a native seed mix to establish competition. Once a healthy community of natives is established, it is important to avoid disturbing it.

Native grasses offer great competition to weeds

Native seed mixes can be purchased in bulk or in 5-pound bags from seed companies or nurseries that will work with you to select the correct mix for your site. I asked Ted Alway, the owner of Derby Canyon Natives in Peshastin for general recommendations. Ted said, “It depends on whether you are working with a dry upland site or a riparian site that gets more moisture. For shrub-steppe, your main component is bunchgrasses that can crowd out weeds and withstand the long dry periods. You can have some woody shrubs like sagebrush, bitterbrush, and wax currant that provide shade cover, but you really want to lead with the grasses. You can also put in wildflowers in your second year after you spray weeds with a broadleaf herbicide.” For riparian areas, Alway recommended planting trees and shrubs such as willow, red osier dogwood, golden currant, serviceberry, blue elderberry, and mock orange. “Two other species that work really well for wetter areas are Wood’s rose and snowberry. They provide good shading and are also great for wildlife.”

Benefits of native plants to combat weeds:

  • Homeowners: Low maintenance and water, visually-pleasing, attracts pollinators and wildlife.
  • Farmers: Great field border, or marginal cropland; an NRCS and Voluntary Stewardship practice; helps stop weeds entering field and controls soil and nutrient runoff.
  • Ranchers: Grasses like Basin wildrye and bluebunch wheatgrass make excellent forage. 

If you want to know more, consult your local nursery or seed company. You can also contact your local University Extension Service Agent, Natural Resources Conservation Service (NRCS) office, or Conservation District.

References
Li, W., Luo, J., Tian, X. et al. “A new strategy for controlling invasive weeds: selecting valuable native plants to defeat them.” Sci Rep 5, 11004 (2015). https://doi.org/10.1038/srep11004

 

Kristi L. Sullivan, Peter J. Smallidge and Gary R. Goff. “Controlling Invasive Species in Woodlots”. Cornell University Cooperative Extension and New York State Department of Environmental Conservation (2015). https://extension.unh.edu/resources/files/Resource000988_Rep1136.pdf

 

“Gardenwise: Non-Invasive Plants for Your Garden”. Washington State Noxious Weed Control Board (2007). https://www.nwcb.wa.gov/pdfs/Eastern-WA-Garden-Wise-PDF.pdf

 

Bird, Susan. “Yakima County Noxious Weed Board: Here’s to a Weed Free 2020”. Yakima Herald (Jan. 18, 2020).https://www.yakimaherald.com/lifestyle/home_and_garden/yakima-county-noxious-weed-board-here-s-to-a-weed/article_13a27a66-8e25-5cd1-9a4d-4f474ccce0b2.html

 

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