Kenny Slocum is the naturalist and natural resource manager for the Clayton County Conservation Board.

I remember when I first moved back home to Iowa, I worked hard to identify plants mostly out of a desire to eat them. I would scour books on wild edibles, go out into the field, find what I thought looked like, say, chokecherry, come back home to double-check the references, and eventually give up because the field never matches the guide.

Foraged plate circa 2015

Eventually, Seek by iNaturalist came along and put those field guides right into the palm of my hand. Even better, the Almighty App rendered moot the tedious process of perusing all “ pink flowers,” or all “August bloomers,” or whatever section I had to examine based on how an author decided to organize his or her guide.

Suddenly, with a simple wave of the camera, I had my identification. Or so I thought.

Perhaps the app learned humility, or perhaps my growing body of knowledge means I only pull it out for increasingly esoteric species/specimens, but these days it seems a little less likely to give me a clean ID.

Moreover, the more I get to follow experts around in the field, the more I have learned the Almighty App often gets it wrong. Now, I am back to cross-checking the app ID with a field guide. “Trust, but verify,” so the saying goes.

The plant that taught me this skepticism lies atop the bluffs at Bloody Run County Park, a place that has taught me many botanical lessons I have written about on this blog before. A tall, showy plant bearing yellow flowers and almost thistle-like leaves (without the spines) shows up there at the end of the summer every year.    

“Large-flowered false foxglove,” I’d confidently assert, for years, whenever I had a hiking partner on the Well’s Hollow trail. Like most naturalists, I would share this information despite the fact that no one asked.

“Aureolaria grandiflora,” I’d say afterwards, proud of myself for remembering the binomial nomenclature and misguidedly demonstrating my “competence”.  

Actual large-flowered foxglove (photo courtesy of Tony Vorwald)

I’d go on to explain that it has indicator status for high-quality oak savannas. Hemiparasitic on the roots of oak trees, this gigantic, beautiful wildflower indicates a history relatively absent of plowing or other disruptions to the soil. The deep, tubular yellow flowers seem prized by bumblebees whose heavy, large bodies can reach the nectar stores deep inside.

It turns out I had the ecology (mostly) right, but the nomenclature entirely wrong.

In common parlance, this plant actually goes by the name “mullein foxglove,” despite being neither a mullein nor a foxglove (cue the “coffee talk” memes from old episodes of Saturday Night Live).

The binomial nomenclature, Dasistoma macrophylla, helps explain the difference between this plant and the closely-related Aureolaria genus. “Dasistoma” stems from the Greek for “woolly mouth,” a reference to the fact that the flowers of mullein foxglove have thick hairs blocking the flower’s opening.

Woolly mouth

Of course, all words are made up, so truthfully the name matters less than understanding the ecology and biology of the plant itself. Like the false foxgloves, this plant appears rather intolerant of disturbance (indicating a high-quality natural area).

Like the false foxgloves, this plant requires the nearby occurrence of oaks, particularly white oaks, to thrive. That means one will not see either plant in a prairie, but only in an adequately sunny savanna or woodland.

But it does have some meaningful differences from the Aureolarias, despite the visual and behavioral similarities.

Dasistoma macrophylla exists alone in its genus, a term taxonomists call “monotypic.” This plant exists almost exclusively west of the Appalachians but east of the Great Plains. More common in southeast Iowa, mullein foxglove occurs only rarely in southwest Wisconsin and has no records from Minnesota; perhaps another case of mistaken identity?

Bonap of Dasistoma

The large-flowered false foxglove (that’s a mouthful), and all the false foxgloves, have a more widespread distribution.

Bonap of Aureolaria

Perhaps the most important distinction between the two, and the one that finally got me to double-check my identification, lies in their life cycle. Aureolaria are all perennial; they come back year after year.

Mullein foxglove, on the other hand, mostly just lives for one year. Occasionally, some plants might exhibit a biennial or rarely even perennial habit, but mostly these plants grow for one season to an impressive height of almost six feet, produce copious amounts of seed, and die off.

the author standing next to tall plants

My eyebrow was raised when, after finding just a few scattered specimens shortly after we began rehabilitating Bloody Run, the population steadily increased year after year. At first I would diligently work around it while trimming the trail.

I would watch with delight each summer when new seedlings popped up near the decaying stumps of slain ironwood from the past winter’s work, a sure sign that I had things moving in the right direction. Until last year.

In the summer of 2024, I finally began to wonder if one could have too much of an ostensibly “good,” or “conservative,” or “rare” plant. The massive, leafy stems of… whatever this thing was, seemed to be genuinely taking over.

Abundant plants

Another clue popped up when a friend from Jackson County posted pictures of the actual yellow false foxgloves on one of his properties. I couldn’t quite put my finger on it, but his pictures looked different.

I had taken for granted the passing similarity between google photos and the misidentification proffered by Seek. After a few more years interacting with my “false” false foxgloves, I realized I’d had the wrong plant all along.

I learned the hairy-throat differentiation between the two, and realized, somewhat disappointingly, that technically Dasistoma macrophylla is less conservative than Aureolaria species – in Iowa, at least.

I also observed that my now-weedy mullein foxglove had become infected by a gall former of some kind. Little bubbles on wilted leaves told me something had found the population, though relatively little information on its insect relationships existed for me to figure out what kind of insect had found them.

Galls

After an unsuccessful attempt to rear the mystery gall to maturity so I could meet the wasp who made it, I wanted to try again this year. I figured I would have ample opportunities; after all, this plant had become so abundant I almost worried about its ability to play well with others.

Lo and behold, this summer, when I venture onto the bluffs overlooking Bloody Run Creek, most of the mullein foxglove looks stunted and sad. On many specimens, leaves had begun to wither before they even flowered, turning black and falling off by late July.

What last year appeared like a jungle had seemingly succumbed to some kind of pathogen that drove their numbers down significantly.

With black leaves

Could the gall-former be to blame? Or perhaps some fungus that, in the drought years preceding this one, failed to achieve the vigor required to parasitize the parasitic plant?

Whatever the cause, it highlighted to me the fascinating cycles, oscillating over months and years and decades, in plant communities. I suspect—and if you’ve read this far you know to take my ideas, and identifications, with a grain of salt—that this plant might exhibit regular boom-and-bust cycles.

It makes evolutionary sense for an annual plant to produce copious amounts of seed that do extremely well in good conditions. Unlike perennial plants, the seedlings of annual species do not have to compete with their parents, and vice versa.

Winter abundance

It likewise makes ecological sense for nature to provide some check on that fecundity. A sudden change in habitat, say by re-introducing fire or doing midstory thinning to encourage sufficient sunlight, could trigger a massive population boom.

With only one or two specimens, insects or fungi or bacteria might not have enough “food” to survive long enough to do damage. But once the population hits a certain threshold, suddenly my mystery gall former might experience a boom of its own and proliferate enough to cross another threshold that starts knocking the population back down.

Ecologists call this “dynamic equilibrium,” a stable state characterized by constant change. The Dasistoma will (hopefully) always be there, but the populations may vary dramatically based on the conditions of a given growing season.

A struggling plant

To observe dynamic equilibrium in action is one of the treats reserved for those with the privilege to visit a site like this year after year, and to try to understand those dynamics is the obligation of a site steward who wants to do right by the land.