Poliothyrsis sinensis: Chinese pearlbloom

by Jonathan Damery, Associate Editor of Arnoldia
August 2, 2018

Poliothyrsis sinensis: Chinese pearlbloom

Poliothyrsis sinensis (1036-85*A) flowering at the entrance to the Explorers Garden. Photo by Jonathan Damery.

As a kid, I was obsessed with seed catalogues. My mom read them with a highlighter, selecting tomatoes and marigolds, zinnias and cucumbers for the summer garden, and I would imitate her, arraying the catalogues around myself on the couch, scrutinizing the photographs, and imagining a garden filled with lurid oddities. Eventually, however, I discovered that some plants look better on the page than in the garden. Take, for instance (no offense to the acolytes), the speckled flowers of toad lilies (Tricyrtis spp.), which are almost always photographed up close, showcasing the seductive origami of the petals and outthrust stigma. But when viewed in real life, the flowers are often dwarfed atop the broad foliage of the plant—a shy and clumsy exhibitionist.

Occasionally, however, you encounter a show-stopping plant en plein air that leaves you scrounging for a nametag or texting identification photos to the keenest horticultural taxonomists in your contact list, and you wonder how the plant could have possibly escaped the status of garden celebrity. You are struck by the flowers: the elegance and class, the absence of gaudiness. Why doesn’t the plant appear in more front yards, hugging the corner of the house? To my mind, one of these remarkable but neglected species is the Chinese pearlbloom (Poliothyrsis sinensis).

Poliothyrisis stands as a small tree, and the most prominent specimen at the Arnold Arboretum occupies a position near the entrance to Explorers Garden (accession 1036-85*A), where the plant is now covered with gently downturned panicles, all the color of buttery cream. The flowers intimate a late-summer wedding, suggesting the cascading tresses of a custom bridal train, carefully stitched to sway just so. Yet it is not just the flowers that matter. Even the leaves are ordered and dignified, hanging downward on bright red petioles and facing uniformly outward, like a sunflower field with all heads turned towards the sun. In the winter, the plant is unremarkable but inoffensive, sometimes the most you can ask of an ornamental specimen in the barren and leafless months. (Certainly the common lilac—Syringa vulgaris—could learn a thing or two.) What I’m saying is that the plant is gorgeous, almost stunningly so. Yet every time I encounter Poliothyrsis in a new place, I’m always scrambling through the mental card files, searching for the name.

The orderly texture of Poliothyrsis (1036-85*A). Photo by Jonathan Damery.

Incidentally, Poliothyrsis sinensis—a monotypic species—was once placed in the now obsolete Flacourtiaceae, a mostly tropical family that taxonomists have described as a “wastebin taxon,” where the anomalous and confusing were filed for lack of anywhere better to go. Taxonomists now place Poliothyrsis in the willow family (Salicaceae), which, although I don’t question the genetics, is about like finding a set of silver Tiffany spoons on sale at IKEA. (I love willows, don’t get me wrong, but it is only the cold desperation of winter that makes us gush about their pussytail flowers.) Horticulturist Michael Dirr once described Poliothyrsis as an “unusual accent, novelty, fool-your-friends plant,” and it seems that even taxonomically, a similar notion has long applied.

I realize this reads like unabashed hucksterism—an embarrassing overdose of superlatives. Ernest Henry Wilson is credited with introducing the plant to the United States—our first accession arrived here in 1909 (collected in 1908)—and yet I have not come across more than a passing reference to the species in his writing, nothing to suggest ardent boosterism. Likewise, Sargent only mentioned the species in the Bulletin of Popular Information among a list of winterkilled taxa in 1918. (It is reportedly hardy to USDA Zone 6). I don’t want to commit the faux pas of the toad lily. You don’t have to plant this yourself, but you should, absolutely, come see it at the Arboretum. Hurry soon to catch the flowers.

5 thoughts on “Poliothyrsis sinensis: Chinese pearlbloom

  1. I have one which I grew from a small plant that I bought at the arboretum plant sale maybe 25 years ago. It survive. It is now planted near the front corner of my house and is in bloom now

  2. Thank you for this witty and very informative article; I am still chuckling over the lilac comment! I had never heard of this plant and was immediatley intrigued with its name starting with the disease “polio.” I did a little research, and for those who not Latin scholars,
    polio means grey: the polio virus infects the grey matter of the spinal cord and the poliothrysis inflorescence shows shades of grey. I will also take this chance to defend the toad lilies, one of my favorite fall flowers with their orchid-like blooms!

  3. I have one which I grew from a small plant that I bought at the arboretum plant sale maybe 25 years ago. It survive. It is now planted near the front corner of my house and is in bloom now. If you would like to see it, send me email. I also have another tree, Acer griseum and 3 large shrubs, Lilac Sunday, Viburnum farreri, and V. x pragense. I got them all at the Arboretum plant sales. I have pictures on Google photos I could send you.

    Anthony Hartman

  4. I’ve noticed this tree the last few years. It truly is gorgeous. Thank you for a lovely article. I, too, am a toad lily lover, but you are right about it not standing out in the crowd. There is one that does shine brighter than most, has darker flowers, but I don’t know its name.

  5. I have a several planted in a site in Stayton Oregon. Two are flourishing and pushing 18′ in less than five years, blooming well. They look a little stressed by mid summer but with no supplemental irrigation in Oregon that makes perfect sense. They promise to large and robust trees some day.

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