Submitted by A Chaney.
Weed’em out is the slogan for the Noxious Weed Control Board (NWCB), and it is great to see growing awareness and actions to slow the spread of invasive weeds like shiny geranium and herb-robert. The hard truth is that much of the invasive plant removal work will only delay the invasion. The necessary step that doesn’t get enough attention is on page four of the NWCB field guide for Western Washington, “Developing and managing healthy plant communities that contain a diversity of native and non-invasive plants will help your landscape resist weed invasions, while meeting other land-use goals.”
Recently the Town of Steilacoom sprayed various patches of herb-robert and/or shiny geranium with an herbicide. While many of us would not use herbicide in our own yards, the labor required to manually remove all the herb-robert and shiny geranium on Town property and rights-of-way is rather high. A reasonable compromise would be to post signs whenever herbicide is applied along a sidewalk or trail, or in a park, so that citizens can avoid the area if desired. Regardless of the removal method, the result is often a barren patch of earth. A common practice is to hope for native plants to move in, but a neglected place will be invaded, almost surely by an invasive plant–it is their nature. What makes them invasive is their greater propensity to propagate than what we have in the native plant community. We may think that we succeeded in removing an invasive, but there is surely some seed left in the ground to germinate next year, or sooner.
To break the cycle of invading invasive plants we have to plant something else that will resist the invasive species. For sun loving invasive plants like Himalayan blackberry, Scots broom, and reed canary grass, a good option is to shade out the site by planting fast growing trees and sun tolerant shrubs. For shade tolerant invasive plants like English ivy, herb-robert, and shiny geranium, they are likely in or near the forest, and replanting with some native plants is still necessary. The replanting just needs to be shade tolerant native species, and more densely planted than we might expect. In either case, follow up hand weeding is necessary to catch those missed invasive seeds that germinate later on.
By the time we can see the invasion from our car, it is likely on the scale that some type of herbicide is necessary as a counter-attack, but the defense lies in “managing healthy plant communities” which we all have to take part in.