aka American water-willow
As spring turns into summer and the water levels in the Potomac drop, the stems and foliage of this aquatic plant appear along the river’s edge, growing out of the water.
Water willow spreads by rhizomes, forming large colonies that help stabilize shorelines and provide habitat for small invertebrates. Many types of bees, flies, and butterflies feed on the nectar or pollen. I don’t know if water-willow could properly be considered a keystone species, but it certainly is ecologically important.
Hundreds of species of Justicia grow in tropical and temperate zones of the Americas and parts of Asia and Africa, but only about two dozen are native to the US. American water-willow is by far the northernmost growing of these species, and can be found as far north as Ontario and Quebec, though no further west than Texas. It’s threatened in Michigan and endangered in Iowa.
Although each flower is relatively short-lived, and only a few are produced at a time, the overall blooming period of the plant can be several months long.
evening clouds reflected in the Potomac