Roadside Weeds

I’ve been out bicycling a lot of miles around Whatcom County this year. While it’s mostly a speed thing challenging myself to see how fast I can go, I’m also observing what’s in bloom along the side of the road. It changes every few weeks, although there are few flowers, like Queen Ann’s Lace, that stay in bloom for a long time.

Japanese KnotweedRight now the showiest plant in bloom is one of our nasty invasive weeds, Japanese Knotweed (Polygonum cuspidatum). There’s some question about the taxonomy, so what we have may well be Bohemian Knotweed (Polygonum × bohemicum), a hybrid species. Regardless, it’s a tall showy plant with drooping panicles of white flowers that forms large masses at the side of the road.  It prefers moist places like ditches and streambanks and spreads by underground rhizomes. It’s very difficult to eradicate as any tiny bit of root will start a new plant and spraying common herbicides seem to only slow it down. The preferred method of attack is to inject herbicide directly into the stems, which is very labor intensive.

I’ve noticed that along some of the county roads it has been mown down, which might help keep it in check. At least seeds won’t set and spread the plant that way. Last winter the plants that hadn’t been cut drooped over onto the shoulder and partially blocked the way along one of the busier parts of one of my regular routes.

Japanese Knotweed is an example of a plant that was originally introduced as a garden specimen and got away. For more information about it and the other big knotweeds see this page from the Whatcom County Noxious Weed Board.

Common ToadflaxAnother pretty roadside weed, not nearly as widespread around here, is Common Toadflax (Linaria vulgaris). It’s only a foot or so tall and covered with attractive yellow flowers. I saw a patch of it along Slater Road near the railroad tracks yesterday. It’s not on the Washington noxious weed list, but its cousin Dalmatian Toadflax is.

Of course, not everything blooming along the road is a weed. I also saw quite a bit of the fall-blooming Pacific Asters on my rides this past weekend. My long ride was a loop out Mt. Baker Highway, down Mosquito Lake Road to Acme, down to Park Road and over to Lake Whatcom, then south past Cain Lake to Alger, and home by way of Lake Samish and Lake Padden. You can see the route on Map My Ride.

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