I came across a reference to a “groundsel-tree” in a novel, and I wonder what its connection is to the weedy groundsel. In the book, it is found growing near the beach at Coney Island in the 19th century.
The weedy groundsel is Senecio vulgaris (a Class C noxious weed in Washington State, with a more colorful common name, old-man-of-the-spring, presumably because of its fuzzy white seedheads), but ‘groundsel tree’ refers to a tree-like deciduous shrub, Baccharis halimifolia. It goes by other common names as well: sea-myrtle, saltbush, consumptionweed, silvering, coyotebush, and salt marsh-elder, to name just a few.
One obvious connection between the weed and the shrub is that they both belong to the daisy family (Compositae/Asteraceae). There is similarity in the shape of the flowers; according to Missouri Botanical Garden, the shrub’s common name “refers to the similar appearance of the tufts of pappus on mature seedheads of this species and those of common groundsel (Senecio vulgaris).” (To me, Baccharis seedheads resemble the brushes on old-fashioned typewriter erasers!) Both plants have toxic properties. The weed is harmful if consumed by cattle or horses, and humans—though less likely to ingest it—can also suffer liver damage or death from eating it. The woody plant has toxic leaves and seeds. Both the weed and the shrub have the ability to spread aggressively, and according to this blog post from Buffalo Bayou Partnership, that trait is embedded in the common name groundsel, “from the Anglo-Saxon groundeswelge, meaning “ground swallower.”
It makes sense that the plant would grow in a place like Coney Island (even in a fictional setting), because it is a salt-tolerant shrub. Baccharis halimifolia is native to the Atlantic and Gulf coastal areas of the eastern and southern U.S.