365 Urban Species. #220: Horsetail

Photos by urbpan. Location: Underneath railway bridge at the Wishkah River, Aberdeen, Washington.

Most of the weeds we admire, revile, or ignore, depending on our own interests, are plants that bear flowers, and subsequently, seeds. But this lifestyle is a relatively recent development, having evolved only about 140 million years ago. Before that time, plants reproduced by emitting spores. The greatest biodiversity of plants today is among the flowering plants, but some of the spore-producing plants are still with us. Mosses and ferns are familiar, but the horsetails are less well-known.

They are tall and straight plants, knotted stafflike stalks surrounded by whorls of thin raylike branches. They appear primeval to our eyes, and are often depicted in artists depictions of prehistoric landscapes. Before flowering plants evolved into trees, horsetails towered over the heads of the dinosaurs. Today there are only between two and three dozen species (depending on what source is reporting) of these once dominant plants.

The species E. arvense, known as common, or field horsetail, is the most widely distributed and most urban. Like many of its flowering competitors, once it is established in an area it is hard to remove, as it regrows from its rhizomes. Though it is considered a native plant in Europe and the Americas, it is an unwelcome weed in agricultural settings--spoiling cropland and poisoning livestock. In urban environments it tends to grow in waste areas, such as along railyards and industrial sites. It tolerates sandy, acid, and saturated soils, as well as soils dense with clay. Another species, giant horseweed (E. telmateia) can also be urban, growing in drainage ditches and marshy areas.


Location: 19th street, Tacoma, Washington.