King County's Weed of the Month: Yellow Archangel (Lamiastrum galeobdolon)
Class B Non-regulated Noxious Weed
Our featured weed this month is becoming one of the plants I get the most questions about, either because it is causing a nuisance for someone or because it has mysteriously shown up someplace unexpected. I suspect it also gets lots of attention because of its distinctive leaves and its tendency to grow in dense, unbroken patches that call out for attention. The silver and green leaves and dense, sprawling growth are part of yellow archangel's attraction as an ornamental in shady beds or hanging baskets. Unfortunately, this is not a plant that stays where it is placed. Time and time again, yellow archangel has shown its ability to sneak away from a planting bed or discarded hanging basket and spread thickly into a nearby forest or ravine.
I have heard of and personally seen numerous examples of yellow archangel sprawling out of yard waste piles or flower beds and into the surrounding woodlands. The first time I saw yellow archangel was just this kind of situation. In the spring of 2000, a homeowner from the Ames Lake area asked for help identifying a plant that was spreading from a small pile of garden clippings she had left in the woods and taking over her forest. Sure enough it was yellow archangel. She had tried to pull it all up from a front garden bed, piled it up out back, and then returned later to find it growing out into the woods. Meanwhile, the area she had pulled was persistently coming back from small roots and stems left behind. I ran into the same homeowner last year and after about 6 years of hand-pulling most of the yellow archangel was gone, although there were still plants showing up occasionally.
This first homeowner's experience was enough to alert us to the potential invasiveness of this plant, but it did take several years of observations and gathering testimonials before it became clear that this was a candidate for noxious weed designation. For example, one homeowner east of Renton described how her native woodland flowers disappeared over a few years as yellow archangel took over in the forest near her house. What really concerned us was that yellow archangel was spreading into forests, not only urban and disturbed areas, but also high quality woodland areas with fairly intact native plant communities. Now that yellow archangel has been classified officially as a noxious weed in Washington State, our goal is to spread the word to gardeners everywhere to avoid introducing this plant near natural areas and to keep it contained where it is already growing. Also, it is our hope that infestations in natural areas will become a higher priority for removal by public agencies and land managers before they become too widespread to control. I was pleased to hear recently that the City of Kirkland will be using volunteers to remove the rather intimidating patch of archangel in their Watershed Park.
Yellow archangel goes by several other names. Its Latin name according to the USDA Plants Database is Lamiastrum galeobdolon, but you will also find it called Lamium galeobdolon or Galeobdolon luteum. Common names that it goes by include simply Lamium, golden dead-nettle, and, most interestingly, weasel-snout. The plants we see escape are all variegated although there is some disagreement about what exact species or variety this is or whether the non-variegated varieties of the same species would be invasive if they were given the opportunities that the silvery-leaved one has. It is best to avoid all varieties of the species, variegated or not, at least here in the Pacific Northwest, until we have more information.
For pictures and information about yellow archangel, there are several good resources on the internet, including the State Weed Board's Written Findings, Paul Graham’s web site on southwestern B.C. invasives, Arthur Lee Jacobson's website, and King County's yellow archangel web page. The information available is still somewhat limited but fortunately Wendy DesCamp, a graduate student at the University of Washington, is researching this plant and will have more detailed information in the coming year or so. Also, I have heard that Tim Miller at WSU Extension will be starting some control trials soon in order to improve our technical information on how to control this plant.
If you have had any experiences with this plant, I am very interested in hearing about it, especially successes or problems with different control methods. Also, I am collecting locations of where this plant is growing un-invited, so please let us know about any locations you see in King County, especially if you notice it growing in an alarming way or in a remote natural area. Although control is not required for this non-designate noxious weed in King County, we are gathering information on distribution and impacts and would like to encourage people to remove it when it is threatening natural habitat. You can call us at 206-296-0290, send an E-mail or use our online infestation form.