Successful weed management depends on using the right methods for the weed and for the site conditions. Many resources exist that can help you identify your weed and provide guidance on how to control or eradicate the infestation. However, if you would like one-on-one advice on weed identification and management methods, you can contact a Habitat Restoration Specialist or Farm Planner or the Snohomish County Noxious Weed Control Board.
If you are dealing with toxic plants or are struggling with noxious or non-native plants in sensitive areas (near streams, wells, lakes, Native Growth Protection Areas, irrigation ditches, or pastures), the Snohomish Conservation District can help provide you with information on how to control weeds in a manner consistent with local regulations.
Prevention is the best line of defense when dealing with weeds. If you notice a new plant spreading quickly on your property, take the time to identify it to see if it is a noxious weed or a plant of concern. If it is a non-native weed, we recommend that you remove it. At the very least, contain the infestation by preventing further spreading by seed or vegetative parts (for example – clip flowering heads of thistle, tansy, and butterfly bush to prevent seed production; do not mow knotweed because the cut pieces flung by the mower can grow into a new plant).
If the non-native weed is already established, you will likely need to use several different methods to successfully control or eradicate the infestation. Control efforts focus on stopping the spread via seed or vegetative reproduction whereas eradication is the removal of the weeds from an area permanently. Depending on your site conditions, the size of the infestation, time of year, and the plant biology, you may need to use a combination of mechanical, biological, chemical and cultural control methods to effectively control or eradicate weeds.
Mechanical control methods include mowing, digging/tilling, burning, flooding, soil solarization (weed fabric), and mulching (exclude light).
Biological control may include grazing with livestock. Grazing can exacerbate weed problems, however, so management practices must be followed closely. Biological control by insects or other agents is managed by regulatory agencies at the landscape scale and is not effective for individual property owners.
Chemical control with herbicides requires strict adherence to the pesticide label. Herbicides and pesticides are commonly over-applied and contribute to the pollution in Puget Sound.
Cultural control methods include planting desirable vegetation to replace weeds, fertilization and irrigation of desirable vegetation, crop rotation, equipment sterilization, and other practices. Cultural control methods are generally a combination of prevention and control.
Transport and disposal of non-native, invasive weeds vary by plant species and by time of year. It is best to review the guidelines for the weed to learn about specific recommendations.
Online resources to help you identify, report, and control specific weed species:
- Weed identification and control strategies:
King County Noxious Weed Control Board (nice photos for identification): http://www.kingcounty.gov/environment/animalsAndPlants/noxious-weeds/weed-control-practices.aspx
Washington State Noxious Weed Control Board: http://www.nwcb.wa.gov/search.asp
- Report noxious weeds on public property in Snohomish County: http://www1.co.snohomish.wa.us/Departments/Public_Works/Divisions/Road_Maint/Noxious_Weeds/