Taisha is again the author. She writes:
Today’s photo is of Equisetum arvense, also known as the field horsetail. This picture was taken by Hans Mohr (aka muscovite@Flickr) on May 19, 2013. Thank you Hans for the vibrant photo (submitted via the Botany Photo of the Day Flickr Pool)!
Equisetum arvense is a perennial species that is found across North America, Eurasia, Asia, and Greenland. Often, it grows along roadsides or riverbanks, or in fields and pastures. Though native, the field horsetail is considered a weedy species in British Columbia as it is poisonous to young horses and sheep when ingested.
Equisetum is derived from the Latin equus meaning “horse”, and seta, “bristle”, a reference to the resemblance of some species to the tails of horses. Field horsetail can propagate vegetatively from an underground rhizomatous stem. Fertile and vegetative aerial (aboveground) stems are hollow, except at the nodes. The shorter, brown fertile stems mature in early spring, shown in today’s photograph. They are unbranched and terminate in a spore-bearing “cone“. After spore dispersal, the fertile stems will wither and sterile stems grow. These vegetative counterparts with whorls of side shoots at the nodes are green and photosynthetic. The nodal leaves on the vegetative stems are dark brown, toothed, and form a papery sheath around the stalk.