On a languid afternoon in July, a pastime to have won the approval of Thoreau would be to stretch out on the banks of the Potomac, journal in hand, waiting for deep thoughts to arise or a wading bird to land nearby. Or if a philosopher considered deep thought too taxing, perhaps best not to contemplate anything at all, just gaze across to Virginia’s shore or up at the intense blue sky. The cicadas’ loud racket made a riverside nap now impossible. Better to admire the tiger swallowtail flapping by, a concentration of black and yellow reticulations. And then a great blue heron lifts off from its hunting pond, on the way to another favorite spot. But cast an eye long enough and a new face appears in nature. What is this bluish-white flowering plant growing in a large mat along the banks? Could it be an aquatic orchid? But since when do orchids grow in water?
It was about twenty years ago as I sat like a poor-man’s Thoreau on a summer’s day that I made this discovery. One of the strangest experiences in nature is to come upon a plant family from the tropics you know well in all its diversity and not realize that there are representatives right in your own Maryland neighborhood. I knew the ground-dwelling orchids in our area, but this plant had me stumped until I counted the petals in its irregular flower and saw the telltale bracts beneath the corolla. Could this be an Acanth? Later I learned about the Carolina wild petunia, but what was this little gem? I consulted some local plant lists and to my surprise discovered that I had spotted an American willow weed, a member of the genus Justicia: some of the most beautiful flowering plants in the world. The Acanthaceae (Acanths for short) are a group of about 2,500 species and can be found from lush rainforests in Costa Rica, Brazil, and Indonesia to the deserts of Namibia. We may know them as cultivated petunias, or to those ornamental lovers, as the vivid yellow and red flowers and bracts of Pachystachys. But there it was, covering the shallows of quiet side pools in the Potomac, Justicia americana, our diminutive American water willow. I suppose it was named water willow because, like willows, it is native to the water’s edge and the leaves are somewhat willow-shaped.
American water willow grows as far west as Texas, and from New England, reaching up to northern Ontario and Quebec, and down to Florida. The reason the water willow grows in clumps is that it spreads from underground stems and can, in the right conditions of water, nutrients, and sunlight, form massive mats covering as much as 1,000 square feet, though I have never seen any colonies that enormous around Cabin John.
I would imagine in the big colonies of water willows, the bee traffic would be something to behold. Each white and purple blossom of the half-inch-wide flowers sports bee guidelines, steering the insect pollinators to their destination, like lines on an airstrip. Butterflies also visit water willow.
It’s a lovely plant to get to know on a hot summer day with nothing better to do. Go look for it. And take your notebook in case the meaning of life strikes you while you sit watching colonies of water willow undulate in the riffles.
By Eric Dinerstein, Contributing Writer
Illustration by Trudy Nicholson, Contributing Artist
