Noxious Weeds of Weber County

A map of Weber County, UT. Dots represent noxious weed populations. Each color is representative of a given species. The blue polygons represent treatment sites for 2023.

Weber County is working hard to manage the invasive plants across the county. The Weed Board, Conservation District, and other entities continue to collaborate through coordinated efforts secure grant funding that targets specific species.

Five species were included in this year’s invasive species mitigation grant: dyer’s woad, yellow star-thistle, Japanese knotweed, phragmites, and garlic mustard. Each of these plants is known to crowd out other vegetation, degrade human-managed landscapes, and contribute to declining ecosystems.

Reports provided by the public provide valuable information that leads to more effective eradication efforts. Currently, the county’s strategy begins with mapping (as seen in Figure 1). After mapping, the county secures funding for eradication and targets predetermined populations each year. The final step monitors eradication efforts from previous years to prevent re-infestation.

In addition to reporting weeds, the Weed Board strongly encourages the public to be proactive and manage annual and biennial noxious weeds early in the growing season. For example, dyer’s woad and thistle are much easier to remove when they are small. Pull, hoe, or spray these weeds in the spring before they flower or go to seed. Breaking these weeds’ reproductive cycle can effectively reduce their population.

Some perennial weeds such as phragmites and Japanese knotweed should be controlled after mid-summer. This is because the plant sends all its energy and sap up from the roots to grow new shoots and leaves each spring. While the sap flows upward, eradication efforts will have little effect on the roots of these species. Without killing the roots, these perennials will continue to re-sprout.

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