The Fundamentals You Need To Tackle Noxious Weeds In Washington

Anne starts by explaining what the Noxious Weed Control Board is, what they do, and how they define noxious weeds. She then gives listeners an overview of some common noxious weeds in Western and Eastern Washington before explaining how noxious weeds impact our environment. 

Then, she gives a detailed explanation of who is responsible for controlling noxious weeds and explains how noxious weeds are classed and what the classes mean. Anne points listeners to educational resources where they can learn more about noxious weeds and what actions they can take to prevent them from taking over. She also gives a quick lesson on innovative strategies used to control weeds and explains what biocontrol is and how it is used. 

She closes out the episode by listing some noxious weeds that are being monitored and gives listeners a link to where they can find free seeds for native pollinator plants to replace noxious weeds.

Anne Schuster is an Education Specialist for the Washington State Noxious Weed Control Board. She received her Masters of Conservation Science from the University of Queensland, in Brisbane, Australia, and her Bachelors of Science & Art from the Evergreen State College, in Olympia, Washington. Before starting with the Washington State Noxious Weed Control Board, she monitored and restored various habitats with Wolf Haven International, the Center for Natural Lands Management, Thurston County, and the Washington State Department of Transportation.

• Washington State Noxious Weed Control Board
• Find Your County Noxious Weed Board
• Unwelcome Guests: What You Need to Know About Japanese Beetles in Washington State with Cassie Cichorz – Episode 024
• Native pollinator seed packet
• YouTube Clip Marsh Master controlling Phragmites in Ocean Shores
• Weed Free Hay and Mulch Program (WSDA)
• Palmer Amaranth | National Invasive Species Information Center

[00:00:00] Erin Hoover: Welcome to the Evergreen Thumb, your go-to podcast for up-to-date research-based horticulture and environmental stewardship knowledge to help you grow and manage your garden. Produced by Washington State University Extension Master Gardener Volunteers and brought to you by the Master Gardener Foundation of Washington State.

I’m your host, Erin Hoover, a WSU Extension Master Gardener since 2015 and a certified permaculture designer and modern homesteader.

WSU Master Gardener volunteers are university-trained community educators who have been cultivating plants, people, and communities since 1973. Are you ready to grow? Let’s dig into today’s episode.

Our guest today is Anne Schuster. She is an education specialist for the Washington State Noxious Weed Control Board. She received her Master’s of Conservation Science from the University of Queensland in Brisbane, Australia, and her Bachelor’s of Science and Art from Evergreen State College in Olympia, Washington.

Before starting with the Washington State Noxious Weed Control Board, she monitored and restored a variety of habitats with Wolf Haven International Center for Natural Lands Management, Thurston County, and the Washington State Department of Transportation.

Anne is here today to talk to us about noxious weeds in general and why it’s important to control them, what we need to keep a lookout for, and some of the resources available to gardeners on managing noxious weeds.

 Anne, welcome to the show.

[00:01:29] Anne Shuster: Hi, thank you.

About the Noxious Weed Control Board

[00:01:31] Erin Hoover: So to start off, can you tell us a little bit about what the Noxious Weed Control Board does and, um, kind of what their purpose is?

[00:01:41] Anne Shuster: So, the Noxious Weed Control Board is a regulatory board, kind of like an agency, that works at the state level, and their primary assignment would be to make sure that the plants that are being listed can be regulated and can actually be treated and controlled, um, because these plants do harm the environment or agriculture or humans.

[00:02:12] Erin Hoover: How are noxious weeds defined legally in Washington?

[00:02:14] Anne Shuster: So, a noxious weed is a non-native plant that can cause serious harm or poses serious threats to Washington, and that means either agriculture, horticulture, human health, livestock, pets, um, any natural resource, including humans and agriculture.

Common Noxious Weeds

[00:02:37] Erin Hoover: So what are some of the more common or more recognizable noxious weeds in Washington?

[00:02:42] Anne Shuster: So the most common noxious weeds really depends on where you are in the state. In Western Washington, everybody sees scotch broom all along the roads. Uh, this time of year I believe is when the butterfly bush is blooming. In September, is when the trees of heaven become very apparent along the roadsides, and those are on both sides of the state in really high numbers.

[00:03:06] In the eastern side of the state, there’s a lot of roadside plants that are noxious weeds, like, uh, white top and orange peel clematis is known in one location.

There are some things that are really showy and everywhere, some of them.

[00:03:23] Erin Hoover: Interestingly, I just discovered that oxeye daisy is considered a noxious weed, and I always thought it was native.

[00:03:29] We have it on our property and so now I’m ripping it out.

[00:03:33] Anne Shuster: Yeah, that is, there’s a lot of that. Almost everywhere that’s open. And it is a Class A noxious weed.

How Noxious Weeds Impact Our Environments

[00:03:40] Erin Hoover: What types of impacts do noxious weeds have on our local ecosystems and in our agriculture?

[00:03:46] Anne Shuster: So it depends on the noxious weed. Some weeds really only impact certain agricultural groups.

So, for instance, Queen Anne’s lace, also known as wild carrot, that impacts commercial carrot growers. English ivy is something that can grow up walls, grow up trees, grow onto power lines, and will kill an entire hillside of trees or ruin the side of your wall or potentially during a storm make it easier for the power lines to fall down because they’ve weighed them down some.

And then other plants are harmful to, say, human health or livestock. So like giant hogweed is a plant that, if it gets on your skin, it causes really bad blisters that can last for years. And it’s edible by goats, but not by other livestock that can get really sick if they eat it.

Who is Obligated to Control Noxious Weeds?

[00:04:47] Erin Hoover: Do property owners have a legal obligation to control noxious weeds?

[00:04:54] Anne Shuster: Yes. So the legal obligation to control noxious weeds is up to each individual property owner.

For renters, it might be in their rental agreement or contract that they have to control noxious weeds, or maybe their landlord has to. That depends.

But for the most part, it’s up to property owners, and that includes government property owners, that includes tribes, that includes, like, municipalities with right of ways, everybody is really up, it’s up to themselves to control noxious weeds with some um, enforcement about it if somebody is going to come and tell them that they have to.

Classes of Noxious Weeds and How Those Are Defined

[00:05:34] Erin Hoover: So you mentioned, um, that oxeye daisy, oxeye daisy is a Class C weed.

What are the different classes and how, what defines them?

[00:05:41] Anne Shuster: It’s a good question. So Class A weeds are the highest priority weeds to remove. They are weeds that are usually rare, or maybe not even in the state yet, and those are the ones that, should they become established, they would cause the highest amount of damage to humans or livestock or whatever they pose a threat to.

So those are required for eradication as soon as they are found, and that has to be completed within one calendar year. And eradication means that all plant parts have to be killed or destroyed or disposed of, um, just made not alive on the landscape anymore.

The next classification down is Class B.

Those are weeds that are maybe very widespread in some parts of the state, but not in others, or pose threats to certain industries, but not others. An example of one would be scotch broom. So scotch broom is a Class B weed and it is designated for control in most of the eastern side of the state, but it’s not designated for control in most of the western side of the state.

[00:06:47] And control means it’s kind of the next step down from eradication. Any part of the plant that can reproduce needs to be destroyed, killed, disposed of, um, just taken off the landscape. So scotch broom, that can mean mowing because it only reproduces by seed. But for knotweed, another Class B, mostly means eradication because it is able to reproduce from basically any plant part.

[00:07:14] And so these plants are chosen where they’re designated and where they’re not designated based on the resources available in that area to control the weeds and also the threat those weeds pose. So, for scotch broom, it’s actually still feasible to control it in the eastern side of the state within one calendar year.

[00:07:37] They don’t have that much scotch broom currently. It’s actually possible to mow it down, keep it down, keep it from spreading. Whereas on the western side of the state, it’s basically everywhere, and the municipalities and the agencies that have to take care of it have limited resources and budgets, so they just can’t do it in one year, and it’s unlikely that it would ever be designated for control or, say, uplisted to a Class A, ever, anytime soon.

[00:08:06] Then Class C weeds are the lowest classification of weeds. Those are weeds that are usually pretty widespread. Sometimes they’re a little bit easier to control. Sometimes they only pose a threat to maybe one industry. Um, like Queen Anne’s lace, like I talked about earlier. That’s, uh, I believe that’s a Class C.

[00:08:26] And these Class C weeds, for the most part, they’re not required for control or eradication. Every county can decide if they want to control the plants, if they want to put it on their local list. But there’s no state mandate that says that they have to. So, you don’t have to remove your oxeye daisy. Um, I don’t think there’s anywhere in the state that’s requiring control of oxeye daisy.

[00:08:50] A lot of times, that third listing, the C list, is used for education, outreach, um, it would be great if you could, but it’s not really likely or feasible given most people’s resources.

The County Weed Board and How They Differ from the State Weed Board

[00:09:05] Erin Hoover: So that kind of leads to where I was going to go next, is that with the county weed boards, how does the work that the county weed boards do differ from the state weed board?

[00:09:13] Anne Shuster: Yeah. So, us at the state weed board, there’s only two of us and we mostly just do legislation, education, and outreach. We work with the board. We work with the board’s committees to make sure they have the resources they need to make their decisions. And we also give a lot of support to counties and agencies to work with each other.

[00:09:36] Then the counties are where most of the weed control and management happens, or most of the counties, all but one county has their own noxious weed board. And these boards decide on the local level what to control and how. They have to take all the Class A’s and they have to take all the Class B’s that were listed in their area, but then they can choose any other plants.

[00:10:00] And then they hire staff and those staff go out and monitor the county work with landowners, work with property owners, work with agencies to actively control weeds, or to get people resources on how to control weeds on their own properties. They also do education and outreach. Um, they’re basically like the local experts actually doing it.

[00:10:24] Whereas I just found out maybe in the last month and a half from the attorney general that, um, me and my coworker, Mary, were not even allowed to control weeds as state employees, we’re only allowed to educate.

What Preventative Measures to Take as Gardeners

[00:10:41] Erin Hoover: What are some of the preventative measures that gardeners can take to avoid the spread of noxious weeds?

[00:10:46] Anne Shuster: So I like to work with the Washington Invasive Species Council on a lot of things that help prevent the spread of not just noxious weeds, but all sorts of invasive species. With them, we do a lot of education and outreach, and they have some actual materials and outreach materials and like, boot brushes that they can give out.

[00:11:06] And there are ways to prevent weeds from spreading from site to site. There are things like the boot brushes that us and the Invasive Species Council give out. So you clean your boots, clean your tires between sites, especially if you don’t know what’s going on, um, in a previous site, or if you think you saw something, or if you think there could be seeds that are viable in the soil, it’s really important to clean those off of your boots, off of your shoes, off of your tires, off your tools.

And using weed-free sources of like, mulch, soil, sand, uh, hay.

[00:11:41] Those are all good things to look for. There are certain certifications that the Department of Agriculture has. I’m not sure about those specifically, but there are resources for weed-free certified materials. And then also knowing what the noxious weed list is and like knowing the plants on it so that you can maybe not plant those plants in your yard.

[00:12:09] So just because they’re on the noxious weed list doesn’t mean that they’re not allowed to be sold in Washington. Every year I get emails saying English ivy is being sold at this one spot. English ivy is allowed to be sold, even though it’s a noxious weed, and that’s because the prohibited plants list, also known as the quarantine list, is administered by the Washington State Department of Agriculture, and they determine what’s allowed to, or not allowed to be sold in Washington, and they haven’t put all of the noxious weeds on there.

[00:12:40] There are some weeds that are grown commercially like ivy and would pose an economic impact potentially to growers and sellers. So they have to do more work to get things to be stopped from being sold. Um, another example of that would be like butterfly bush. It was sold for a long time, just commercially and anybody could get it.

[00:13:04] And then it became a noxious weed. Then people realized that they could grow sterile cultivars of it. These sterile cultivars are now the only ones that are allowed to be sold. And even though they’re sterile, they still have like 6 percent seed viability.

[00:13:19] So it’s still not great. And they can still reproduce asexually in moist soil. So that’s not great, like, if you live along a creek or a river. But for the most part, that is stopping new butterfly bushes that are actually able to reproduce from invading our lovely landscapes.

[00:13:37] Erin Hoover: Yeah, I actually had some, um, knotweed from some compost.

[00:13:42] Fortunately, I knew what it looked like, and when it came up in my garden, I was able to get it out right away, but it was already like a foot tall by the time I found it.

[00:13:49] Anne Shuster: Knotweed is really hard to kill off in composting, uh, I guess, facilities. They have to get really hot to kill it.

Noxious Weed Educational Resources

[00:13:55] Erin Hoover: I bet, yeah. So, uh, what educational resources are available for gardeners to learn more about noxious weeds?

[00:14:03] Anne Shuster: So, on our website, we have PDFs, and you can also order for free physical copies of a lot of our booklets. So, we have gardening guides. We have field ID guides. We have individual pamphlets for plants. And then, in addition to those publications that we have PDFs of, and you can also get mailed to you for free if you just go to our website, uh, then you can also get, we have a page for every single noxious weed, with how to identify it and how to control it, uh, pictures, helpful links.

[00:14:41] Lots of counties have made their individual control sheets, control fact sheets, and we put those on our website. So, there’s information on so many noxious weeds and also with those booklets and other information that we have, we have lots of information on alternatives to plant in your garden or how you might want to follow up with control because if you just control it, it probably isn’t good enough.

You probably want to replant with something specific.

[00:15:10] Erin Hoover: All right, well, we’ll put a link to that, to the website in the show notes so that everyone can find those resources and hopefully identify any noxious weeds in their garden.

[00:15:20] Anne Shuster: Oh, we also just got in our native pollinator seed packets. So we have small packets of seeds that we are giving out available for free.

[00:15:32] You can order those on our website as well. Uh, also you can reach out to your local county weed board to get those because they have most of our stock.

Innovative Strategies to Control Noxious Weeds

[00:15:45] Erin Hoover: So, can you share any innovative solutions or strategies that have been developed, um, to combat noxious weeds?

[00:15:53] Anne Shuster: So one of my favorite innovative strategies is biocontrol. It’s not new. Biocontrol has been going on for a long time, but biocontrol is where you release an animal or a pathogen into the environment that, goes after a certain other, in this case, plant.

[00:16:13] So, for instance, Tree of Heaven is having biocontrol researched on it on the East Coast where they have a lot of Spotted Lanternfly. Spotted Lanternfly are a big threat to agriculture, both on the East Coast and on the West Coast. They’re not here yet, but when they get here, they will be. So having a biocontrol for one of their major host plants, which is tree of heaven, would be really important because trees are hard to kill.

[00:16:41] And so if we can get, I don’t know, all the things they’re researching, but they’re probably researching some flies and some funguses that can kill tree of heaven. Things I just saw recently are (I saw the researcher at WSU), she is working on a, it’s kind of like a fruit fly. They’re very, very small flies that will lay their eggs inside of knotweed and then kill the knotweed.

[00:17:11] And so right now she’s doing experimental releases of these little, tiny flies and these biocontrols. People used to just release things willy-nilly all the time. I did my master’s degree in Australia, and Cane Toads are a famous example of a biocontrol where somebody just thought, oh, I’ll release that, and that’ll help.

[00:17:35] They released Cane Toads, which are these frogs from South America, to eat mosquitoes in cane fields, and it turns out the cane toads don’t live in cane, sugar cane fields, and they don’t eat mosquitoes, and they’re poisonous, and they eat everything, and they kill wildlife all the time. So, we don’t want things like that to happen anymore.

[00:17:57] They used to happen a hundred years ago. We have better research and better science now. We don’t have to just release things. So, researchers like, uh, Jennifer Andreas at Washington State University research very, very, very in-detail specific lines of fungus and specific lines of insects that can be released that won’t feed on anything but this one noxious weed.

[00:18:21] And we get it down to where it won’t have any host plants outside of that. So it can’t harm anything else.

An example of another biocontrol that wasn’t thoroughly thought of, thought through, before it was released is the Cinnabar Moth on tansy ragwort. So Cinnabar Moths were released for a long time because they control tansy ragwort.

[00:18:45] The problem is, they eat lots of other things too. They don’t just eat tansy ragwort. And so now there’s been really great research, and I think they have at least two, maybe three species of other biocontrols that are being released on tansy ragwort and controlling it.

Oh, and these biocontrols are really good for areas that are far away from people, where it’d be hard to get backpack sprayers in, or places where nobody wants to hike in and do monitoring and hand remove, you know, thousands of plants.

[00:19:17] These biocontrols don’t eradicate the weed, but they get it down to a level more like it would be in its native range because now it finally has a native-to-it herbivore or disease.

[00:19:31] Erin Hoover: Um, I remember one of the controls that I saw, I think it was with, um, invasive grasses on the coast in the dunes.

[00:19:40] This, giant machine, it looks almost like a tank. It’s like pushes down the grasses to stunt the growth of the invasive grasses on the coast.

Anne Shuster: I’ve seen those.

Erin Hoover: I saw one on a truck a couple of months ago. It was coming into our area.

[00:19:57] Anne Shuster: Those will also go into like wet marshy areas to get aquatic weeds. They’re pretty amazing.

What is the Highest Priority in Weed Control Right Now?

[00:20:02] Erin Hoover: So, what is the highest priority weed for control in Washington right now?

[00:20:09] Anne Shuster: So I’ve talked about tree of heaven a couple of times already, and in my opinion, it is the highest priority weed to control in Washington right now.

[00:20:33] As I sort of alluded to earlier, tree of heaven is the really preferred host plant for Spotted Lanternfly at a certain point in Spotted Lanternfly’s life cycle. Um, they don’t rely on tree of heaven, but they reproduce a lot better if they have it at some point in their nymph’s life cycle when they’re younger than adults.

And these Spotted Lanternfly, they’re not in Washington yet, but they are along the East Coast and they’re spreading every day. They pose a very serious threat to Washington.

[00:20:56] They will cause billions with a B, not millions, of agricultural damage to Washington when, not if, they get to Washington. They feed on basically any crop we grow.

Spotted Lanternfly will feed on hops, they’ll feed on grapes for wine, they’ll feed on apples, they’ll feed on all kinds of stone fruit. They also will feed on a bunch of our native plants, like big leaf maple, which are already stressed out from lots of hot summers.

[00:21:25] They feed on quite a few of our other native plants, um, in Western Washington and Eastern Washington. When these philodendron flies feed, they poop out this really sweet, sticky substance that then grows mold, and that mold is what mainly damages the plants. So these plants will just be covered in these insects that are draining them and pooping on them and causing them to get moldy.

[00:21:51] And if we can get rid of all of the tree of heaven, then Spotted Lanternfly will do much worse here. They won’t be able to be quite as fecund, they won’t reproduce quite as well. Uh, they might be more susceptible to diseases, or just being caught, successfully caught in mass numbers because they just, won’t be quite as strong.

[00:22:18] It would be really great if we could control all of the tree of heaven. Tree of heaven is, like I said, it’s a tree. It grows all over the state. Right now, we’re updating our maps of where we know it is. The old map from I think 2018 shows it mostly along the Columbia River Basin, but with the Washington Invasive Species Council, we did a citizen scientist survey of tree of heaven in, I believe, 2021. They are in high numbers in every county in the state, pretty much.

[00:22:44] And they are very apparent in September. That’s the most obvious time to see them because that’s when the female trees have big bunches of seed pods. You’ll see them all along I5 on your way to Portland, um, all along the Columbia River Gorge.

Uh, they’re very apparent trees.

Emerging Noxious Weeds to Monitor

[00:23:08] Erin Hoover: Um, actually, I, just a few episodes ago, I spoke with Cassie Chichorz from the Washington State Department of Agriculture, and we did talk about Spotted Lanternfly for a little as well. So, I will put a link to that so people can go check that one out, too.

So, are there any emerging plants of concern that we need to keep an eye on, um, that may be headed this way?

[00:23:30] Anne Shuster: So every year the Noxious Weed Control Board updates the Noxious Weed List with plants that are coming in and things that are on the horizon. One that just got listed last year, it was even in an emergency listing. It didn’t come in during the normal proposal period, which happens from January 1st to April 30th.

It came in from an expert in Eastern Washington around July, so that’s kind of late in the process. And that is Palmer amaranth,

That is an amaranth. It’s, um, pigweed that some, that’s what some people might call it, that is really bad for certain, like, annual crop growers. It will absolutely take over fields.

[00:24:16] It reproduces so prolifically. I don’t know how many thousands or millions of seeds an adult plant makes. Uh, it only grows for one year and then it dies, but in that one year, it grows really well. They can get like seven feet tall, they shade out all the plants underneath it, and then the seeds stay viable in the soil for a long time.

[00:24:39] They’re pretty herbicide resistant, so once we get them, they’re really hard to get rid of. They develop herbicide resistance really quickly. There were two infestations found in Washington in the middle of 2023, and that’s why we had the emergency listing of it. Both of those were eradicated very quickly after being found and identified.

[00:25:01] They’re going to have to monitor those sites for multiple years. They had to pull those plants out by hand because herbicide wouldn’t work. They did genetic testing on the plants, and they found that they’re probably resistant to glyphosate and a few other herbicides that are commonly used.

Another bad thing about Palmer amaranth is a lot of other states won’t accept seeds or produce to be sold into their states if Palmer amaranth seeds are present.

[00:25:31] Palmer amaranth seeds are really, really small, so that would just add even extra hardship to agricultural producers if it were to get established.

So right now, there’s no Palmer amaranth known in Washington. There are a couple sites known in Idaho and Oregon, and it’s being monitored. It was listed as a Class A at the end of 2023, so it’s required for eradication as soon as it’s found.

[00:25:58] And we really want to keep it out, because it would be really bad, especially for Eastern Washington crop growers.

Final Thoughts or Any Final Noxious Weeds to Add?

[00:26:05] Erin Hoover: I think that about covers the questions that I have. Did you have anything else you wanted to add?

[00:26:11] Anne Shuster: Oh, I wanted to add for tree of heaven, you can tell it apart because it smells bad. Um, a lot of its lookalikes have, uh, serrated edges on their leaves, but also their leaves don’t smell bad.

[00:26:23] And tree of heaven have smooth leaves, leaf edges, and if you mush them a little bit, they smell like rotten peanut butter or cat vomit. Um, it’s gross. It’s really gross. So that’s another reason to remove them. You don’t want that in your yard. The flowers smell like the leaves do. They’re bad. It’s gross.

[00:26:40] Erin Hoover: All right. Well, thanks so much for joining me today. This was really good information and, um, hopefully, we can help, uh, control some noxious weeds.

[00:26:49] Anne Shuster: Thank you for having me.

[00:26:49] Erin Hoover: Thank you for joining us on this episode of the Evergreen Thumb. Brought to you by the WSU Extension Master Gardener Program Volunteers and sponsored by the Master Gardener Foundation of Washington State.

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