Northwest Office

Northwest Regions

Looking to the Past and Future When Managing Invasives

By Cathy Lucero

Clallam County, which is wedged into the northwestern most corner of Washington State, encompasses some of the best tree-growing country in the world! It has also been the battleground for some of the most contentious environmental conflicts over endangered species, in particular, the spotted owl, but also anadromous fish and many more. By the late nineties, much of our forest industry was scrambling to adjust to lower harvest quotas, complex habitat plans, and stream setbacks. The term “sustainable” harvest was said everywhere, but just how that was to be determined or achieved was hotly debated.

This was the setting when, 20 years ago, I became the first noxious weed control coordinator for the recently activated Clallam County weed board. I had a newly minted environmental science degree and a background in botany. Most of the 100-plus weeds on the list were weedy species that colonized open disturbed areas and caused significant agricultural impacts and economic losses. Therefore, most of our efforts focused on infestations in and around agricultural lands.

However, a slow and nearly invisible invasion that begun decades ago picked up momentum. Scientists were now sounding the alarm about profound ecosystem impacts caused by rogue ornamentals, as well as seemingly helpful, but increasingly harmful, non-natives that had spread far beyond their intended range. As awareness of these effects on an increasingly diverse range of habitats grew, so did Washington’s agro-centric weed list. In 1997, there were 106 invasive plants species on the noxious weed list; fast forward to 2020 and there are now over 160. Many are shade tolerant, and at least four non-native invasive trees have been added. There are 51 species sitting on a monitor list as we collect more information and ponder whether these “monitor” species are aggressive and harmful enough to warrant listing and potential regulatory action; five on this monitor list are trees.

How is it that so many plant species became problematic, and why will the noxious weed list continue to grow? We all know that even the best-intentioned actions can yield unpredictable results. For example, broadcasting non-native species like everlasting pea-vine, as a good wildlife forage (not!) as well as erosion control, (too good!) has enabled this resourceful pioneer species to become an overpowering competitor in young reprod units.

Even forests are vulnerable

For decades, usually only Scotch broom and some of the thistles were recognized by the forest industry as problematic for tree regeneration, but these problems could be addressed with routine site preparation. In the dense forests of my region, most foresters viewed invasives as simple nuisances that would drop away as soon as the canopy closed.

It turns out forests aren’t as immune as we thought. The impact and burden of invasive species on forests has only become more evident with time, but so has our recognition of the value of healthy forests in our community, in terms of jobs, economy, and renewable resource and sustainability. By 2004, a serious threat to tree production and forested habitats emerged in the form of an assemblage of woody, invasive Polygonum species, often lumped together and called Japanese knotweed. Closer investigation revealed not one, but several distinct although closely related species: Japanese, Giant, and the aptly named, Bohemian, a particularly aggressive hybrid of Japanese and Giant knotweed parents.

Much has been written about knotweeds, as if straight from a script for a ’50s horror film of an experiment gone terribly wrong. These prize-winning ornamentals were introduced into the United States in the late 1800s, but in Washington State were noted only as far back as the ’30s in close association with railroads and logging activity. The theory of origin in Washington is that very young shoots were cultivated by camp cooks for use as early spring greens. Nearly 90 years later, the camps are gone, but knotweed is not. Instead knotweed spp. are running rampant along many river corridors, creating living walls that halt forest succession, altering stream flow, disrupting complex food webs, and creating a biological desert. Long thought to only readily colonize open habitats, our experience in Washington has proved otherwise. Over the years, knotweed thickets have formed massive monocultures spanning hundreds of acres containing little to no other vegetation, including trees. Invasive knotweeds have proved to be remarkably persistent, and like most noxious weed problems, require a consistent, multi-faceted, long-term commitment to combat successfully.

In Washington State, the Olympic Invasive Working Group surveys for and removes knotweed, a Class B weed on the noxious weed list. Photo courtesy of Cathy Lucero

Building partnerships around invasives

As the magnitude of threats posed to forests by knotweed and a host of other more recent non-native invaders has emerged, so has a coalition of unlikely partners. As my job title suggests, I am always looking to coordinate and bring the people solution to bear on the invasive problem. To that end, in my little corner of the world, the Olympic Peninsula, we have formed a cooperative weed management area (CWMA), dubbed the Olympic Knotweed Working Group. Fifteen years later, and much expanded, we’re now the Olympic Invasive Working Group. Land managers of both public and private forests, environmental groups, Native American tribes, governmental agencies and regulators work collaboratively to combat common adversaries that know no jurisdictional boundaries. We share information about what works and what doesn’t, as well as new threats posed by invasive plants and sometimes animals. We pool our workforces when we can and inspire each other to be alert and keep up the effort. This loose consortium is designed to support and empower individual partners with crafting an effective response to invasive weeds on lands they manage while taking into account their organizational structure, resources, and specific management goals.

For the forests in Clallam County and elsewhere in the Pacific Northwest, a significant vector for invasives is contaminated road-building materials. For that reason, most federal, and many Washington State agencies now include weed-free material language and standards in their contracts. Clallam County Weed Control Board staff, funded by the Olympic National Forest and the Clallam County Road Department, is authorized to inspect and certify rock sources. With the support of these two entities, we offer free inspections and a report with customized, practical, remedial actions to meet agency standards. By working together, we can ensure that projects aren’t delayed, and forests of all kinds are protected in the long term.

In addition to actively controlling existing infestations in forests, weed boards simultaneously pursue measures to prevent the spread of invasives. The solution, like the problem, lies with people. So when you hear, “I’m from the government and I’m here to help,” don’t laugh. Even though the weeds on our list may shift over time, the fundamental mission and overarching goal of weed boards in Washington State has not. We are charged with aiding our communities by protecting and preserving the land, our natural resources and our environment. Get interested, get involved. Talk to us. Let us know how we can help.  Even if you don’t live in Washington, there is someone, some group that is focused on dealing with invasive species. We’re here for you. 

Cathy Lucero is the Clallam County Noxious Weed Control coordinator. She can be reached at 360-417-2442 or

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