Yellow Archangel – April 2019 Weed of the Month

Yellow archangel (Lamiastrum galeobdolon) stirs up a lot of passion for some people, usually very negative. It is one of the plants we get the most questions about, either because it is spreading like crazy or because it has mysteriously shown up someplace unexpected. I suspect it also gets lots of attention because of its distinctive green and silver leaves and its tendency to grow in large, unbroken patches in forests.

Yellow archangel with silver-green leaves and yellow flowers

Yellow archangel with silver-green leaves and yellow flowers.

Yellow archangel crowding around a fire hydrant in a wooded park.

Yellow archangel crowding around a fire hydrant in a wooded park.

The bright silvery evergreen 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 put. Stem pieces, roots and seeds all help this plant spread beyond where it is planted.

I have seen many 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. Six years later, after hand-pulling it regularly and diligently, there were still plants showing up occasionally.

This 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. Another unlucky gardener was trying in vain to keep it from spreading into the forested park next to where she had planted it. She said it was much worse than English ivy because of how hard it was to control; it just kept coming back each time she pulled it! In areas all around the county, yellow archangel was spreading into forests, not only urban and disturbed areas, but also high quality woodland areas with fairly intact native plant communities.

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Yellow archangel growing into a park outside the fenced in yard where it was planted.

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Yellow archangel carpeting acres of forest understory in rural King County.

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Yellow archangel spreading down a steep, forested slope on Squak Mountain.

Other counties in western Washington had similar experiences with yellow archangel and the State Noxious Weed Control Board added it to the Noxious Weed List in 2007. It is currently a Class B noxious weed that is required for control in some counties where it is still limited in distribution. This doesn’t include King County, where we have way too many infestations and lots of people still using it in their gardens. See the State Weed Board website for more information, and the yellow archangel map for the current statewide distribution.

Even though yellow archangel is too widespread to require control in King County, we do try to spread the word to gardeners to avoid planting it near natural areas and to keep it contained where it is already growing. In 2016, the Washington State Department of Agriculture added yellow archangel to the quarantine list so nurseries no longer sell it in Washington. In time, this should help reduce the new infestations and allow us to catch up and control the ones that are already here. King County land managers are working hard to reduce it where they can, but this is often a multi-year effort.

Yellow archangel, which is in the Mint Family, has yellow tubular flowers on little leafy stalks that rise above the foliage. Look for blooms from April to June. You can spot the plant all year long because the silver and green leaves are evergreen. The leaves grow in opposite pairs that resemble wings (thus the name “archangel”) and are toothed on the edges. Like most plants in the mint family it has square stems. It also has rough hairs all over and an interesting smell, not minty exactly but distinctive.

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Yellow archangel starting to flower in early April, with leaves that are still somewhat purplish from the winter.

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Yellow archangel’s opposite leaves look like wings. Plants in King County are always variegated, silver and green.

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Yellow archangel has square stems like most plants in the Mint Family.

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, yellow 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.

Yellow archangel grows in a sprawling, loosely matted pattern that covers the ground and other low-growing vegetation. It doesn’t climb exactly, but it will scramble up and over small bushes and stumps, even up the base of trees. It is a true groundcover in the sense that it leaves no room for any other plants.

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Yellow archangel is a ground cover, growing densely along the ground and crowding out other plants.

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Yellow archangel has a sprawling, semi-climbing growth pattern.

Yellow archangel is stoloniferous, meaning it spreads by forming roots along the stems as they grow along the ground. If stems are broken off, they can form new plants wherever they land. The roots are thin and easily broken off when the plant is pulled, allowing it to re-grow readily from what is left behind. It takes diligence, patience and attention to detail to hand pull this plant effectively.

Even controlling it by covering it up with tarps or mulch is challenging because it can survive in the dark for months and often finds little cracks and crevices to emerge through the covering or mulch. And, as if we didn’t have enough to worry about, yellow archangel also can spread by seed, although this seems to be less common then spreading by stem fragments and stolons.

yellow archangel seedlings and re-growth Rinneke Dierken

After being removed, yellow archangel can show up again from seedlings and re-growth. Left alone, this will quickly become filled with yellow archangel again.

Yellow archangel is at its most vigorous in a shady woodland, but it does fine in sunny areas too, and tolerates lots of different soil conditions from damp to dry. It is very shade tolerant – growing just fine under a thick canopy of blackberry or in the otherwise bare zone around the base of a cedar tree. I admire the toughness of this plant, but unfortunately in our part of the world it can do serious damage crowding out native forest wildflowers and other plants.

If you spot yellow archangel growing in the wilderness or forested natural area, please report it to the land manager! In King County, you can use Report-a-Weed online or get King County Connect, the county’s customer service smart phone app. Both reporting tools can be accessed here on our website.

For more information about yellow archangel:

King County Noxious Weed Control Program

Washington State Noxious Weed Control Board

University of Wisconsin-Madison Master Gardener Program

And from local plant expert and garden writer, Arthur Lee Jacobson, writing about yellow archangel’s worrisome nature way back in 2003

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Yellow archangel is so distinctive, it’s easy to spot growing where it shouldn’t.

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If you happen upon some yellow archangel while hiking, stop and snap a photo and report it. There’s an app for that – King County Connect here in King County or EDDMapS.org anywhere in the USA.

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This yellow archangel patch was spotted and reported by trail weed watchers at the upper trailhead of Twin Falls Trail.



Categories: Tips, Weed Control, Weed Identification, Weed of the Month

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2 replies

  1. Have this weed all over my back yard, at least it doesn’t look terrible but it seems impossible to control.

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