“Is this thyme?!?”, I remember my teenage mind questioning at the sight of foliage that resembled the herb. It was March, and I was rummaging through the fencerows near our house looking for wildflowers on a cloudy day that couldn’t decide if it was winter or spring. Per usual, nothing much was to be seen since I lived in the avoidance zone, but my blitheful, naive self still held out hope I might find something in the leaf litter.
And, here it was. I knew enough about herbs to cue in on the small, elongated leaves stooping down. The foliage looked a bit more pointed than the mother of thyme clump I had back home, but I crushed some, and it released a spicy menthol smell supporting my teenage hypothesis. “Wow, I’ve discovered thyme from some old homeplace,” I said to the forest around me.
Looking back on the whole experience now, I chuckle. I didn’t know about Occam’s razor then. Nor, did I pause to critique my thinking with questions like how has thyme survived in this underbrush, or how has it not spread out and taken over creation?
No, back then I knew thyme wasn’t native to the US; therefore, I assumed someone planted it here. It still had its low winter foliage just like the herb in my garden.
So, I transplanted it home and nurtured it. And, then it started to grow. And grow and grow and grow until it was over two feet tall. This plant was not thyme! I went through a wildflower book I had and found a match in the Lamiaceae section—Pycnanthemum tenuifolium.
Pycnanthemum tenuifolium flowering en masse.
Narrow-leaf mountain mint is currently blooming in my garden, and seeing it flourish was a fun reminder that I make mistakes and learn from them. Sometimes when we are wrong, it turns out better than we could have imagined! Some fifteen years ago in my teenage years I didn’t realize what I had discovered—one of the best native perennials for pollinators and other insects.
I’ll go ahead and address the white elephant (or, should I say white-flowering herb!) in the room. Yes, as a “mint” it can spread some, but I’ve never had the issues with it that I’ve had with other Pycnanthemum or Mentha species. I see having more of it as a good thing. Even with its vigor, I lost the clump I found along the roadside. But, a few years ago, I began to hunt for plants for creating floras. I knew where Pycnanthemum was; therefore, I decided to saunter back along the same fence row in search of it. After a few hours, I found one inflorescence. I collected a piece from that Tennessee plant and some seed, and this germplasm became the basis for our plants that we use on campus. Years later, I would find local Texas ecotypes on the road. Both are blooming now in my garden and offer so much.
A haze of Pycnanthemum tenuifolium flowers over a perennial planting at my house.
The fine-textured foliage emerges in tight columns rising upward. In bud the plant makes me think of the constellation Crux, or the southern cross, for the haphazard dots that attempt to form perpendicular lines. After flowering I enjoy seeing the seedheads that persist well into winter.
X marks the spot on Pycnanthemum tenuifolium. Since the inflorescences are cymes, that character likely generates this interesting floral architecture.
But, the flowers are the pinnacle attribute of this plant. The blooms remind me of stratus. Instead of countless moisture particles composing a flat, gray-white cloud that blankets the earth, here hundreds of mithril-colored flowers form sheets that hover over the foliage. These dense flowers are the origin of the name Pycnanthemum (pycn- means dense, and -anthemum refers to the flowers).
And, the insects that flock to this all-you-can-eat-buffet is astounding—bees, wasps, flies, butterflies, and more that I’m missing. Research has shown Pycnanthemum tenuifolium to be a great niche for beneficial insects from providing resources for native bees to creating habitat for predators and parasitoids. I’ve observed that the plant buzzes most with activity in the middle of the day. I have plants near each other to accentuate their seasonality, and for the pollinators it makes cloud hopping even easier.
A zebra swallowtail waddling through the flowers on Pycnanthemum tenuifolium. Yes, I know you can’t see motion in this still picture, but trust me. It waddled.
A giant swallowtail probed Pycnanthemum tenuifolium flowers.
The other day I took advantage of an overcast sky to take photos of my narrow-leaf mountain mint. I smiled at the similarity of seeing the dark insects dart amongst the silvery-white flowers and how they resembled the shadows of birds circling above me in a broken, gray altostratus sky. Both looking for food and both trying to live. This national pollinator week, I recommend planting this perennial in abundance in the garden so that you, too, can have a richer life and enjoy the clouds of Pycnanthemum and all the life that comes with it.