common yarrow – Wildly Mistaken

Common yarrow (Achillea millefolium) was one of the earliest plants I added to my butterfly garden. It definitely attracts pollinators and it showed up on several lists of best plants for my area. This spring, I even gave some to several neighbors because of my success with it. Soon after, I was forced to reconsider the whole enterprise when I saw yarrow on a list of non-native, invasive species for this region. What exactly was going on here? Did I make a mistake years ago that had perpetuated all this time? Was there some new information about this plant? What else might I be wrong about in all my dedicated efforts to plant a mostly native garden? Was my whole crusade to support biodiversity a fool’s errand?

I started researching with a lot of my go-to sources. Sure enough, some of them showed it as non-native, others as native, and still others as… both. They didn’t all agree on the scientific name, either. What? So I started using search terms like “yarrow native range” and “yarrow native distribution,” which shed very little light on the matter. Instead my search presented me with phrases like “native to the Northern hemisphere” and “cirumboreal distribution.” This was about as useful as when you’re eight and a grown-up asks you where you live, and with a mischievous grin you say: “Earth.”

A wild specimen at Blue Mash Nature Trail

Further reading started to clear this up: yes, it is native to Asia, Europe, and North America and yes that native range more or less includes all of the United States… but it’s also much more complicated. I was beginning to see how a plant could be both “native” and “introduced” to the same place, but I wasn’t quite getting it until I came across this excellent piece. Nowhere else could I find all of the pieces of the puzzle so elegantly combined. I won’t try to do the same here but essentially it is a species complex, there are many cultivars, and human interaction with the plant is extensive. Some of what we call Achillea millefolium is native, some is not, some may have characters of both the native and non-native varieties, and good luck to any non-biologists determining if an individual specimen is locally native!

The linked history with human activities makes me start thinking in circles. That interaction is over such a long time scale that it blurs the line between native and introduced. If humans aided its distribution, but over tens of thousands of years in lockstep with our own expansion, was that a natural process? This to me is an astonishingly fascinating question. It is certainly much different than one guy bringing a hundred starlings to a new continent, but is it also different from a plant gradually increasing its range as its seeds are distributed by birds? If so, just how different? Where is the line between humans as a part of nature and humans disrupting or interfering with nature? How we answer these questions can shape the very core of environmentalism, and I doubt there is one right answer.

This started as one small plant in the corner of this large stump.

Aside from that rabbit hole of natural philosophy, I also needed to decide if I still believed common yarrow was a good choice for my butterfly garden. Are its native or invasive characters stronger? I don’t immediately disregard all non-native plants in my landscape choices, but I do typically steer clear of anything that’s a known invasive in my area. I have noticed that this plant spreads aggressively – as predicted by every source I consulted years ago. Most of what I have planted is the white-flowering, “natural” variety and not one of the brightly-colored cultivars. It does provide the ecosystem function of attracting pollinators and it is a host plant for some local butterfly species. I can control the spread in various ways and it is hardy and low-maintenance. Is it a net benefit to the local ecosystem? I could envision a reasonable defense of either position based on my understanding of the available facts. A purist might say that with no way of knowing for certain that your plant is a locally native ecotype (or technically a native species at all) one should never include that plant in support of biodiversity. A non-purist might counter that because it serves the ecological function of a native, and some related forms are native, there’s no reason to exclude it. I believe in this case there are angels on both shoulders who happen to disagree.

For now, I am listening to the angel on the non-purist shoulder. I will be looking to replace any brightly-colored varieties with other plants, since I know for sure those are cultivars. I will keep the white-flowered specimens I have and manually restrict their spread. It hasn’t (so far) choked out any of my other plants, but there are plenty of other avenues to adding yellow and pink blooms to my garden for color balance. Fortunately, this isn’t an irreversible decision. I’m perfectly willing to reevaluate a matter this cloudy now and again. I am still building my knowledge base on Maryland native plants and as my familiarity with other species increases I may find there is no longer room for a plant that walks in both the native and invasive worlds.

If you’re reading this, odds are you know a butterfly garden has been a passion project of mine for several years now. It has gone well, and increasingly so each season. I have obsessed over every plant (or other feature) included, constantly asking questions like “can I get away with this non-native?” and “Do I have room for more of this, or do I need to diversify?” Each species has been meticulously chosen and cared for. I have stood among the blooms in midsummer, certain in my hubris that everything was proceeding as I had foreseen.

Then one day this summer I discovered it wasn’t. Hadn’t. Didn’t – whatever.

In one small spot beside the garden bench grow several plants with feathery leaves and clusters of white flowers. They have spread well and stayed green through the last two winters. I grew them from seeds marked “pearly everlasting.” When I bought these seeds, I searched by the scientific name Anaphalis margaritacea, because a common name is notoriously slippery thing. I marked the pots as pearly everlasting, treated the plants as pearly everlasting for garden planning and plant maintenance purposes, referred to them as pearly everlasting in this blog, offered pearly everlasting seeds to fellow gardeners, identified wild specimens of this plant as pearly everlasting… you can see where this is going.

The “pearly everlasting” in all its glory.

Is there a worse feeling then finding out you have been confidently, defiantly wrong about a verifiable fact, and acted to perpetuate that wrongness? I’m sure there is, but this sensation always guts me when it happens. I try very hard to either be correct or admit uncertainty. It’s humbling when I am reminded that sometimes it just doesn’t work out that way.

So how did I come to discover this error? There is a second flower that has been on my to-plant list for the past couple years: common yarrow (Achillea millefolium). This spring, a couple of different factors led me to realize I already have this plant! First, I was scrolling through some local observations on iNaturalist. I came across a plant with the suggested ID “yarrow.” I thought “gee, that really looks a lot like pearly everlasting.” I was tempted to suggest this, but a quick Something image search of the scientific name made me hesitate. I left this incident believing these two plants look awfully similar. They don’t, if I’m being honest. A few days later I was researching yarrow in preparation for adding it to my garden. This finally brought me to reality. Every photo of the white-flowered variety looked exactly like my familiar plants. This time I decided to also image search pearly everlasting and compare. Nooooooooooooope!

Thinking back, it’s stunning just how much information a pre-conceived notion can brush aside. Those seeds were labelled “Pearly Everlasting – Anaphalis margaritacea,” and plants grew from them. From that starting point, my brain steeled itself against assault from any evidence to the contrary. I remember thinking the seedlings didn’t look quite like what I’d expected, and ignoring that. I remember thinking the flowers didn’t look quite right when they bloomed, and dismissing that. I remember seeing yarrow plants for sale and wondering why they looked so much like my “pearly everlasting.” I remember squinting at photos of pearly everlasting in field guides and gardening books until they looked close enough to satisfy me.

Blooms of a colorful variety of yarrow I added this year.

What the hell, human brain? The tricks our brains can play on us in confirming our own biases are well-known, but that doesn’t lessen the impact of catching them in the act. It invites one to surrender to radical skepticism and cease trying. That’s not particularly productive, though. Instead I will try to re-instill some basic lessons of identifying organisms.

Consider as many field marks or features as are discernible.
Do not reject any details, whether or not they conform to expectations.
Do not make assumptions about field marks or features you can’t see.
Seek additional opinions if there is any doubt – and preferably if there is no doubt.
Using dichotomous keys never hurts, even if it is especially tedious for familiar species.

I could keep going, but it boils down to keeping an open mind and replacing assumption with observation. I suppose I could call it a scientific approach. I don’t think matching observations to existing literature is properly “science.” However, the process (question, research, hypothesize, test, analyze/conclude, communicate) can and should loosely be followed. It is also not bad advice to be skeptical of one’s own conclusions.

I did end up purchasing some colorful varieties of yarrow to complement the white-flowered crop. Now I find myself in need of a plant I thought I’d had almost from the beginning. I did name my blog “Wildly Mistaken” for a reason, but that doesn’t mean I have to like it when I find out I am exactly that.

Wildly Mistaken

Tag: common yarrow

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