King County’s noxious weed team tackles several high-priority species in April

Crossposted from KCWeeds

King County’s noxious weed specialists have their hands full this month and it isn’t going to get easier anytime soon. Top priority noxious weeds they are focusing on this month include garlic mustard, European coltsfoot, giant hogweed and shiny geranium. Other regulated noxious weeds that are following close behind are spotted knapweed, wild chervil and sulfur cinquefoil. And that’s just the short list of priority species that are regulated under Washington’s state noxious weed law.


King County weed specialists can help homeowners remove their giant hogweed if they aren’t able to do it. Photo by Sarah Baker.

Garlic mustard is probably the most challenging species we are chasing this month. It is a Class A noxious weed so we are trying to find and eliminate every plant, but it is one of the most difficult plants to locate.

This month garlic mustard is producing taller, flowering stems, so it will be easier to find. But it also means the clock is ticking if we are going to control all the plants before they set seed.

In large, forested areas like Coal Creek Natural Area, garlic mustard has a tendency to blend in among look-alike forest plants like nettles and fringe cup. Along waterways such as the Cedar River and Big Soos Creek or steep hillsides like the forests of Golden Gardens and Carkeek Parks, the terrain is another challenge, making it difficult to even get to the plants to control them.

We have contacted property owners and asked for access to survey and control garlic mustard. It will be a big help if anyone receiving a request responds quickly so we have more time to get to all the properties. In King County, anyone who has garlic mustard on their property can contact our office and we will come and control it. Stopping garlic mustard from spreading is just that important!

Another scary plant for us is European coltsfoot (see feature article in this blog), just added to the noxious weed list in 2018. This month is the perfect time to look for the plant because both the leaves and the flowering stems are visible in most cases. The flowers are starting to fade and form seeds though, so we need to act quickly to prevent spread.

This year’s rhizomes will start to grow also, so this is a great month to control European coltsfoot no matter what method you use. Because this plant is so brand new for us, we are still learning the best way to control it. If you have experience with controlling this plant, we’d love to hear from you.

European coltsfoot is often spread by fragments of rhizomes carried by water and soil erosion, but also carried in contaminated rock and gravel materials. We have found it growing in places near construction, in gravel piles and along waterways.

Shiny geranium is also in full force right now. We are finding an alarming number of new locations, some of which are quite large.

Even though this plant doesn’t seem that bad – it’s small and not even poisonous – people who have dealt with it in Oregon have warned us just how invasive and pervasive it can be. Probably we are at the point where we still have an opportunity to keep it from establishing everywhere, but it’s a small window that is closely quickly. Please can help by looking for and reporting shiny geranium whenever they see it.

Giant hogweed is still just emerging this month and won’t start flowering for another couple of months, but it is so conspicuous that we can usually spot it even when it’s small.

Hogweed sap makes skin hyper-sensitive to sunlight and often causes burns and blisters to anyone who is unlucky enough to come in contact with it. Gloves, long sleeves and eye protection are highly recommended when controlling hogweed plants. Young plants can be dug up but make sure to get the whole root. Here in King County, please let us know if you see any hogweed so we can work on getting rid of it before anyone gets burned.

Here are a few more regulated noxious weeds King County staff are targeting this month.

Spotted knapweed

The most abundant of the knapweed species on the noxious weed list, spotted knapweed gets taller this month and can be easier to find. The leaves are grayish-green and deeply lobed and old brown flower stems from last year might still be visible. This plant is most common in really gravelly, well-drained soils like you might find on a roadside, railroad edge or along some riverbanks and gravel bars.

Wild chervil

This relative of parsley and carrot is not as scary as poison-hemlock or as tall, but it is very invasive and can be tough to get rid of (see feature article in this blog). Most of the large infestations in King County are in the area between Enumclaw and Auburn, but it is possible that other populations have escaped notice. Identification can be difficult, so it’s best to get an expert opinion on this one. Look for small white flowers, stems that are entirely green and ribbed or furrowed, leaves that are highly dissected, and plants that are about two to three feet tall when in flower.

Sulfur cinquefoil

Sulfur cinquefoil is another noxious weed that can escape notice until it completely takes over. The leaves are distinctive with their 5 to 7 toothed lobes that resemble a hand. However, the leaf color blends with the grass it usually grows with and the pale yellow flowers are not that much help either. Once it gets established, sulfur cinquefoil can crowd out even grass as it forms a dense monoculture. We find this plant all over the county, but it is most troublesome in areas with low-nutrient, rocky soils where it has a big advantage over grass and other plants.

For the whole list of noxious weeds we are looking for, check out the King County Noxious Weed List. Species that are regulated are on the top of the list, either Class A, B or C regulated species. Property owners (and that includes public agencies like ours) are required by our state noxious weed law to control these species to prevent them from spreading further.

In many cases, we can help property owners control their regulated species, especially Class A noxious weeds that are the highest priority, so make sure to get in touch if you are having trouble tackling your noxious weeds. Also, King County residents can help us by reporting locations of regulated noxious weeds on our online reporting form or by contacting us.

For more great photos, visit the original post on the KCWeeds blog.