Invasive Removal - Green Everett Partnership
Invasive Removal - Green Everett Partnership

Invasive Species Awareness Week

Just like these non-native plants, Invasive Species Awareness Week is back!

On a basic level, most invasive species are non-native organisms (plant, animal, insect, etc.) that have been ‘introduced’ into an environment. Because they’re not native, no natural predators exist to control their spread. This allows the invasive free rein over the ecosystem and eventually leads to a monoculture—meaning after a while, the invasive completely takes over. This is the primary reason invasive species are bad, they kill, crowd out or otherwise remove native species and biodiversity from our environment. For more details on invasives, check out this post.

This year, in honor of Invasive Species Awareness Week, we asked the experts what their “favorite” invasive is and the gory details behind their love-hate relationship with these plants.

Charlie Vogelheim

Forterra – Stewardship Coordinator

What is your favorite invasive weed? Garlic Mustard!

Why is it special to you? It is objectively fascinating but practically terrifying. It seems like the franken-weed that was designed specially in a laboratory to have all of the characteristics to make it a super-competitor: each plant produces thousands of seeds, it can easily spread in undisturbed forest areas, it is allelopathic (it releases toxins in the soil that inhibit other plant growth), and it tastes horrible to herbivores. Deer actually help its spread by browsing on everything in a forest BUT the garlic mustard.

Do you have a favorite Garlic Mustard memory? My housemate and I once harvested some to eat after hearing that the plant is edible. We served dinner for our other housemates that night and tossed some in the salad we were serving without telling, thinking it would add a spicy garlicy zing to the salad. None of us were prepared for the gut-wrenching bitterness and our housemates all yelled at us for trying to poison them. While it is not toxic, apparently only the very young leaves of this plant are actually palatable.

Where in WA can it be found? While some small populations have been found throughout the state, King, Clark, and Skamania counties have the largest infestations. It can be found in forested understory area.

What should we do if we find it? TELL SOMEONE! This is a Class A noxious weed! It has not truly “infested” Washington yet and ecologists suspect it can easily get out of control if not managed early. If you see it, call the Washington State Noxious Weed Control Board or your county’s noxious weed office. If it is on your property, you must remove it. Hand-pulling is the most effective method for small infestations but be sure to remove the entire root.

Erin Haley and Sayward Glise

King County – Riparian Noxious Weed Control Specialists

What is your favorite invasive weed? We wouldn’t go as far to say favorite, but the weed we are most obsessed with is invasive knotweed, because it takes up about 90% of our time.

Why is it special to you? Knotweed control often takes us to remote, beautiful places on King County rivers. And sometimes we get to use boats. Which is awesome.

Do you have a favorite knotweed memory? One of the guaranteed best days of the season is getting to survey/treat the upper reaches of the South Fork Skykomish River. It is the most gorgeous stretch of river we have ever worked on and the knotweed population is now almost nonexistent. Whenever we work there it reminds us why we work so hard to restore and protect our rivers from invasive plants.

Where in WA can it be found? Knotweed could potentially grow in any terrestrial/emergent habitat in the state of Washington.  It is a very vigorous weed. We are most concerned about it in wilderness and riverine habitats because of the threat it poses to biodiversity in our native ecosystems.

What should we do if we find it? If you have invasive knotweed on your own property, King County Noxious Weed Control Program’s website (kingcounty.gov/weeds) is a great place to start learning about how to effectively control knotweed. If the knotweed is not on your property, contact your county weed control program or report a sighting using the free Washington Invasive Species Council app (search for WA Invasive in Google Play Store or Apple iTunes App Store).

Chris Tolonen

City of Redmond – Parks and Recreation Maintenance Lead

What is your favorite invasive weed? The term favorite assumes a desirable quality in something, that of which I don’t feel is applicable to invasive weeds. However, my least favorite is knotweed as it is usually seen choking out riverside habitats, one of my most beloved of ecosystems.

Do you have a favorite knotweed memory? When I first moved to western Washington in my naive 20’s I was unaware of the problems surrounding invasive plants. The first time I saw knotweed growing along a river I was fishing or kayaking I thought it was simply beautiful in its delicate, chartreuse foliage! Little did I know, I would eventually never want to see this plant growing in this environment again.

Where in WA can it be found? Primarily along creeks, rivers and roadway ditches.

What should we do if we find it? Contact King County Noxious Weed Control Program or visit kingcounty.gov/weeds.

Bridget Kelsh

Seattle Parks and Recreation – Natural Areas Crew

What is your favorite invasive weed? My “favorite” invasive weed would have to be Himalayan blackberry.

Why is it special to you? It’s the one I’ve battled the most and there is something heroic feeling about removing its chaotic oppressive tentacles to open up the landscape for natives. I started in the pre-pesticide days and dug out many epic root balls – such a satisfying feeling!  Just don’t go back to the site next season….

Where in WA can it be found? It seems to grow everywhere in Washington and after a long season of removal I found myself feeling responsible for every spring, even on non-parks roadsides and empty lots and yards.

What do we do if we find it? I am grateful for the evolution of our restoration program to using pesticides. No more back-breaking root balls to dig out for pesticide professionals like me. Now when I find it I either cut it down to size with a hedge trimmer or loppers and come back a few weeks later to spray regrowth or I cut canes near the ground with loppers or pruners and paint the stems with glyphosate. It’s still a prickly pain to pull out the canes, and still satisfying to reveal the potential native forest or meadow once it’s done!


Matt Mega

Forterra – Green Cities South Sound Project Manager

What is your favorite invasive weed? Common Tansy

Why is it special to you? Because it provided that a ha moment for me. Common Tansy with their yellow button flowers and very interesting leaf pattern look so nice, but they are not friends of our natives. It is the plant that lets me discuss looks are deceiving and just because something looks nice it might be hiding something.

Do you have a favorite Common Tansy memory? Learning the difference between Common Tansy and Tansy Ragwort its sinister cousin.

Where in WA can it be found? Pretty much everywhere, but grows in full sun.

What should we do if we find it? Common Tansy is pretty prolific and spreads pretty easily. The best way to remove is in early spring before flowers form. Dig up completely as broken roots can sprout. High heat composting in local yard waste is recommended. If you are removing non-seed plants, on site composting can be used with monitoring.