Even in a drought, noxious weeds can take over a property with ease, but, after a couple of days of rain recently, areas not watered like a garden may start to see quite the bloom of unwanted plants.
The Reflector recently asked Kevin Tyler, lands management division manager for Clark County Public Works, a few questions regarding noxious weeds. Clark County Public Works has a staff of 14 on the Noxious Weed Management Team who control noxious weeds on county lands, including parks, roadsides, natural areas, mitigation sites and stormwater facilities.
“Some staff are also responsible for enforcing state noxious weed control laws and ensuring private landowners, cities and other agencies do their part,” Tyler stated in an email. “Rain or shine, our team is out there, boots on the ground. There is a lot of area to cover across Clark County. We try our best with what we have, but we know we can’t reach every square mile of land.”
Tyler said the most abundant invasive plants in the county are garlic mustard (Class A), poison hemlock (Class B designate) and tansy ragwort (class B designate).
Garlic mustard thrives in shade and quickly crowds out native plants in forest understories and along trails and waterways, Tyler stated. Its seeds can survive many years in the soil, forming a seed bank that allows it to persist year after year, requiring many years of consistent control effort, Tyler added.
Poison hemlock is poisonous to humans and animals — pets and livestock. Consuming any part of the plant can be fatal. There are many known infestations across Clark County on private property, public lands and roadsides, Tyler added.
The plants have been well-established in Clark County for many decades and present an ongoing struggle.
“The plant is toxic to livestock — particularly horses and cattle — and humans when consumed whether alive or dried. The high amounts of alkaloids in the plant is what causes poisoning, digestive issues and liver damage,” Tyler stated. “Typically, animals will largely avoid eating it if they have enough good forage available. It is still toxic when dried in hay bundles and is usually more palatable to livestock and harder for them to avoid.”
With those three most common weeds in Clark County consistently establishing new populations, Tyler stated that there are some new players in the county.
“While some of our more widespread noxious weeds like tansy ragwort and poison hemlock continue to show up in new and known locations, there are a couple of weeds that have recently caught our attention,” he stated.
A new focus has recently been lesser celandine, also known as figwort and fig buttercup. It is a low growing plant that can be up to 12 inches tall, typically with yellow flowers, which is capable of forming dense mats that can exclude many native plants, Tyler stated.
“It can be found in a variety of environments like forest understories and stream banks but at this time it appears to be most widespread in lawns and landscaped areas in Clark County,” he stated. “Typically, this plant starts coming up in mid to late February and begins to disappear around the beginning of April, providing a short window of time for control. It primarily reproduces from tubers and bulbils (a small bulb on the stem) and depending on the subspecies by seed; all of which are easily spread by people, animals, vehicles and mowers.”
As with many plant species, there may be a native counterpart that looks similar. Tyler stated that there is a native plant called yellow marsh-marigold that it can be confused with and it is sometimes mislabeled as this at garden centers.
“While there are several differences, one way to distinguish these two is by when they flower. While lesser celandine typically flowers in late winter, yellow marsh-marigold starts flowering in late spring after lesser celandine has disappeared for the year,” Tyler added.
For new property owners or people who may even have weeds show up to their patio planter box, Tyler stated that there are numerous online resources to learn more about controlling noxious weeds. To learn more from Clark County Public Works, visit clark.wa.gov/public-works/noxious-weed-management, where users can access the 2025 Clark County Noxious Weed List and report any noxious weeds found across the county.
What can homeowners do to help combat noxious weeds?
Tyler answered with key options for citizens to help combat pesty plants.
“If you suspect you have a noxious weed, contact us for info,” he said. “We are always happy to help identify noxious weeds and to help community members come up with management plans. Call us at 564-397-6140 or email us at nox@clark.wa.gov.”
Tyler provided three key tips for property owners to do their part in the effort against noxious weeds:
