A perennial flowering plant, Campanula rotundifolia, native to the Northern Hemisphere, with blue, bell-like flowers.
Erigeron canadensis (syn. Conyza canadensis), an annual weed
especially, common mare's tail (Hippuris vulgaris)
Equisetum, a fern ally
A long streaky cloud, spreading out like a horse's tail, and believed to indicate rain; a cirrus cloud.
Any aquatic plant of the genus Hippuris, having narrow leaves in whorls.