The One Hundred Plants You Don’t Want Anywhere Near Your Garden! (Though they are probably already there)

Greg Rabourn talks to education specialist Sasha Shaw of the King County Noxious Weed Program.

There’s a new list of state noxious weeds for 2015. It’s just like the Emmy Awards, but even more noxious. The government sees the list as an organizing tool to try and figure which sweet little plant might just hide a thuggish, dangerous disposition.

And just like other awards, there are different categories, with different levels of obnoxiousness.
Class A weeds are serious but there aren’t many yet, so they might still be controlled.
Class B, think Butterfly Bush, is still limited to just portions of the state.
Class C are the ones that are commonplace. Blackberry is Class C. So is Field Bindweed. But you knew that, seeing as how you can take your eyes off a patch for a day and come back to find it buried in bindweed. Its little white flowers can’t hide bindweed’s nasty streak.

There is a new thug on the list this year. Italian Arum, or Italian Lords and Ladies. Gardeners know it. Shaw says there is so much already around, it can’t be stopped.

The same goes for a new grassy Class A noxious weed, a showpiece ornamental called Ravenna Grass. You can buy Ravenna Grass at nurseries around the state. Too bad, because it turns out all the purplish bronze heads waving in the wind have spread seeds to fields around the state. It’s just one more invasive weed turning unique native habitats into some a new kind of environment. Native habitats are disappearing under the onslaught on noxious plants and animals.

Noxious weeds ruin forests, fields and streams. They hurt the economy, harming agriculture and raising costs for governments and homeowners. Maybe the worst damage they do is to our native environments. Noxious weeds end up winning a lot of the battles, shutting out native plants, denying wildlife habitats, turning our fairly friendly NW forests and fields into nasty thickets. Blackberries come to mind. We love the fruits, but who loves the thorns. Some scientists consider the spread of invasive weeds the biggest threat to native habitats around the world.

The weeds can devastate ecosystem benefits that whole populations depend on, destroying access to freshwater in some places, destroying habitat for insects that pollinate crucial food crops in others.

Some noxious weeds make it into new areas thru garden sales. Others are spread by wind, water or wildlife into industrial sites, fallow fields and disturbed areas. Seeds take a ride on pant legs, car tires, even those sweet bouquets your kid picked for you on a field trip. Some homeowners may unknowingly be breaking the law by allowing noxious weeds to grow and spread on their property.

Some plants are quarantined by Washington state’s agriculture departments Shaw told Greg. They can’t be sold at nurseries at all. The federal government also has a quarantine program.
You’ve encountered state agents at the borders asking you if you have purchased fruits or sometimes even nursery plants in an adjoining state. These quarantines are set up to try to keep the invasive out.

Some plants on the list still escape, like Scotch Broom and Japanese Knotweed, both of which are spreading across vast areas.

There is no national agreement on the sales, and sometimes even the importation, of many plants. That may be why it’s often only after a plant has proven itself a nuisance that it makes in on to some noxious weed lists. By then, it is usually too late.

Once a plant has escaped and has become established in the environment, the Department of Agriculture has determined that quarantine would be ineffective, Shaw says, and education is the better approach.

The noxious weed list is their tool to spread the word. So is the King County Weeds of Concern list. Shaw says the list is prepared in order to educate folks to plants that aren’t designated noxious but still have a deleterious impact on native environments.
One of the new plants on the list is Bishop’s Weed. It is an ornamental plant that brightens up dark gardens. It also spreads by roots and fragments. It is a weed of concern, spreading across parks in King County.

The very thorny Black Locust tree is on the weed of concern list this year. So is Bird Cherry, the root-stock of many cherries. Both are invading forests. You can guess how bird cherry is spread.

Efforts to curb some plants can run counter to economic interests. Ilex Aquifolium, English Holly isn’t on the state noxious weed list, though it is being monitored.
It is a weed of concern for King County.

According to a paper published in the late eighties, it isn’t known when Holly first showed up in the Northwest, though a shipment from Europe is documented as being received in 1869. Commercial production began in the 1890’s. 40 trees were planted on a farm in Puyallup in 1891, with harvesting commencing in 1898. In 1986, Holly brought in over two million dollars to the region’s economy. Back then the NW supplied over 85% of the world’s crop.

In 2010 King County tried to get the English Holly listed as a noxious weed. The NW Holly Growers Association successfully pushed back, arguing that there is no definitive evidence that Holly is invasive. The trade association argued that listing the plant would be devastating to their industry.

On Vashon Island, which Sarah Shaw says could be called Holly Island, many stands of Holly thrive in Vashon’s now not-so-native forests. Holly shows up in native forests in California as well, where the plant is also being monitored.

Shaw says people should particularly be on the lookout for Poison Hemlock.
Watch out! It is a deadly poison and it is showing up in P-Patches, where it looks a lot like carrots. Shaw has even seen Poison Hemlock growing in carrot patches.
How to tell the difference? The Hemlock has white roots. The stems have reddish or purple blotches and the leaves look a little different than carrots.

poison hemlock


You can take a class to learn more about identifying and controlling noxious weeds. The next King County class is May 6th in Kent, Washington.

There is a lot of information available online about noxious weeds and their impacts.

Check the links in the article as well as the extension agencies in your county for information and classes.