Common Yarrow: An Uncommon Conundrum

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.

One plant marked for removal…
…and another

Butterfly Garden Plant Profile: Milkweeds

I thought I would try something new, and start profiling each of the plants (or plant groups) in my butterfly garden as a complement to some of the more macro-level discussions I started with. There seems to be no better place to start than with the milkweeds (Asclepias sp.) Plants of this genus are the only hosts for North America’s most iconic butterfly, the monarch. They also attract a wide variety of other insects, for a variety of reasons. Several species are native to the mid-Atlantic, and a few others grow well here. I haven’t found any of these on lists of invasives, so I have chosen to include a sampling of both native and non-native species in my garden. I can confirm anecdotally that monarchs will readily use all as host plants and that many species will take nectar from the natives and non-natives alike.

common milkweed

Common milkweed (A. syriaca) is a native plant with lovely spheroid clusters of white-and-pink flowers. It can grow 5-6 feet (or more?) tall in good conditions. This is one of the first plants I started in my garden for perhaps obvious reasons. I have seen it in action hosting monarchs, milkweed tiger moths, swamp milkweed leaf beetles, small and large milkweed bugs, red milkweed beetles, and more. Seemingly every pollinator will make a stop at the flowers. It is fairly easy to grow from seed, especially if cold-stratified first. It seems to handle relocation well. This plant will thrive in moist but well-drained soils, but in my experience it will tolerate most conditions. I am always nervous about cutting back plants mid-season, but because monarchs prefer young leaves and breed in Maryland later than milkweeds emerge it is good practice to do so. The milkweeds can handle it.

swamp milkweed (amid some partridge pea)

Swamp milkweed (A. incarnata) is quite similar. As its name suggests, it does prefer things a little bit wetter. Mine hasn’t taken off quite as well as the common milkweed, but it does return each year. Its flower clusters are smaller and not the same near-spherical shape, but do tend to a brighter pink. The leaves and seed pods are narrower. Other than the wetness, the same plant care notes apply to swamp milkweed. I know it hosts monarchs and the swamp milkweed leaf beetle and I suspect the other insects mentioned above can eat it as well. It’s a great alternative to common milkweed for a wetter space.

Asclepias tuberosa
butterfly weed (with oleander aphid infestation)

I am still trying to establish some butterfly weed (A. tuberosa). I had read that this species can take a little longer than the others to get going, and this is proving true. Butterfly weed has bright orange flowers and clear (as opposed to milky) sap. So far none of my seedlings from previous years has survived – I don’t know if I have been choosing the wrong location, experiencing a run of bad luck, or something else, but I will keep trying. The orange would really be a nice accent to the rest of my garden’s color pallette. It’s also reportedly a great nectar plant for many pollinators, and since biodiversity is my ultimate goal any native plant that fits the host/nectar profile is a plant I want.

The Maryland Biodiversity Project lists nine additional species (plus two subspecies of swamp milkweed) as Maryland natives. Some appear to be quite rare, and others are limited to the coastal plain. The remaining few species are on my list of potentials for future plantings – clasping milkweed (A. amplexicaulis) looks particularly attractive. I’ll have to balance diversifying the milkweeds with filling other niches, though, so they may have to wait in queue for a few years.

I did mention non-natives, and thus far I have tried two of these. Last year I added some bloodflower (A. curassavica), a more southern species that nonetheless grows well here.  I couldn’t resist the striking red-and-yellow flowers or the glossier green of the stems and leaves. I have observed monarch caterpillars munching on this plant and many insects taking its nectar, so I feel vindicated in sneaking in this non-native plant for variety’s sake. This year I am similarly experimenting with “showy” milkweed (A. speciosa), which is from the western half of the continent. I’m not sure if the seedlings survived the deluge we got earlier this month, but if they did I look forward to seeing if these perform as well as the bloodflower.


I haven’t had too many problems keeping milkweeds healthy once they’re established. One exception is the occasional infestation of oleander aphids. Perhaps coincidentally they have attacked my swamp milkweed most voraciously. The point of my garden is of course exploitation by animal life, but this non-native aphid does not contribute positively to the ecosystem so I don’t tolerate them. Fortunately they seem fairly easy to control. I have found manual removal to be very effective. I simply squish them by grasping the plant stems and rubbing, then rinse the gross yellow goo with a hose.


All in all, milkweeds are low-maintenance flowers that add a lot of visual interest to a garden. They check a lot of boxes in terms of ecological niches as well, even excluding their well-documented relationship with monarch butterflies. There’s very little not to like.

Speaking of “Mistaken”

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.

  1. Consider as many field marks or features as are discernible.
  2. Do not reject any details, whether or not they conform to expectations.
  3. Do not make assumptions about field marks or features you can’t see.
  4. Seek additional opinions if there is any doubt – and preferably if there is no doubt.
  5. 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.

Butterfly Garden Progress Report Part 2 of 2

I shared Part 1 of this piece back in August. To recap, by “progress” I mean “how much wildlife has my habitat garden brought to my yard?” Last time I covered the most obvious category – butterflies and moths – and today I will focus on everything else. This all comes with the same caveat as before: I have no baseline wildlife survey to compare this to. I’m really just making a self-congratulatory list of wildlife sightings in my yard. Somehow, I am OK with that!

Before I move on, I do want to briefly mention four additional lepidopterans since August: the eastern comma (Polygonia comma), tobacco hornworm, aka Carolina sphinx moth (Manduca sexta), raspberry pyrausta moth (Pyrausta signatalis), and giant leopard moth (Hypercompe scribonia).

An eastern comma dining on some persimmons with yellowjackets.

Insects, Non-Lepidopteran

Insects are an overwhelmingly diverse Class of animal life. I will never be able to identify to species every insect I find in my yard. There are plenty I can, though (especially with help). I’m able to put many more into the appropriate Family or Genus. Based on that, I am able to confidently list 90 insect species for my yard, including the butterflies and moths from the last post. That number doesn’t precisely represent individual insects confidently identified to species, although there is only a little fluff. “Fluff” in this case just means an insect I am very confident is a different species from any of the others included. For example, my garden was visited by a juvenile praying mantis for about a week last year. I can’t tell the difference between a Carolina and a Chinese mantis at that stage, but I can certainly say it wasn’t an ant or a caterpillar. Bees and wasps I can treat similarly: I can spot the difference between a yellowjacket and a bumblebee but am not well-versed in recognizing the individual species of each.


Spiders are tough. When I get a photo to review, I am often confronted with notes like “identification to species requires dissection,” or find that I need to be able to see a very specific detail very clearly. Consequently, despite encountering certainly thousands of spiders I only have 16 species on my life list. Of those, only six have I found in my yard. They are: marbled orbweaver, basilica orbweaver, orchard orbweaver, woodlouse hunter, broad-faced sac spider, and Pholcus manueli. I can add at least four “fluff” species (a green crab spider, a jumping spider, a grass spider, and a brownish orbweaver) for a total of ten.

Mecynogea lemniscata (3)
A basilica orbweaver tending its distinctive egg sacs

Other Invertebrates

Isn’t that specific? As much as I hate to lump all this together it’s so much more convenient than typing up categories for each individual kind of invertebrate. I am not enough of an expert to ID many of the included creatures precisely anyway. So what do I have here? The wood tick and house centipede are present for sure. I’ve found earthworms, pill bugs, harvestmen, centipedes, and millipedes of an unknown number of species each. At least three species of slug round out the list. That’s another ten animals in total, under the most conservative of estimates.


Thanks to eBird, I have very good data on the bird species I have spotted in my yard. It comes to forty-three species, and while none of these is particularly uncommon and five or so are merely flyovers, that feels like a pretty good number. And yet… just a few blocks away in Wheaton Regional Park birders have collectively tallied over 170 species. I’ve found more than sixty there myself. I won’t likely be attracting any, say, spotted sandpipers to my yard… but there is some room for improvement.

Zenaida macroura (6)
A mourning dove, an eastern towhee, and some white-throated sparrows beneath one of my feeders.

Cardinalis cardinalis (21)


This is a short and boring list (but try telling my dogs that!) Eastern gray squirrel, eastern fox squirrel, southern flying squirrel, eastern chipmunk, eastern cottontail, Norway rat, white-footed mouse, white-tailed deer, human, dog. Add some unidentified species of mice and bats, and it’s an even dozen. I do think the dogs somewhat cut down on the mammal population I might otherwise see here… I have after all come across groundhogs and foxes in the neighborhood and I know raccoons, possums, and skunks are about. As irritating as the rat population is, at least they’ve never made it inside.


An even shorter, but hopefully less boring, list:

Northern green frog


gray (or possibly Cope’s gray) treefrog


American toad (no one needs a picture of one of these, right?

And that’s the list! So to recap, that’s a grand total of: 90 insects, 10 spiders, 10 other invertebrates, 43 birds, 12 mammals, and 3 amphibians – 168 total animal species cataloged in my yard. All my instincts say that 168 is a big number, yet as I mentioned above more species of birds alone have been recorded in our neighborhood park.