Equisetum pratense is a rhizomatous, branched member the horsetail family (Equisetaceae) that occurs widely in Denali and is found in forests, meadows and river terraces. Horsetails have rush-like stems with ridges of siliceous tubercles and produce spores in cones. Equisetum pratense grows from a dull black rhizome. The sterile and fertile stems are of two kinds in E. pratense. The sterile stems are whitish green and branched, to 80 cm long and 4 mm wide. The central cavity is one-half the diameter of the stem. The branches are whorled, horizontal to drooping. The sheaths on the stems brown teeth with a blackish rib. The fertile stems grow up to 25 cm tall. When they first emerge they lack chlorophyll, are not fleshy and are unbranched. After the spores are shed they become green and may form a few short branches. The sheaths are light green to yellowish white with pale teeth and dark ribs. The cones are peduncled, up to 4 cm long, and rounded at the tip. Equisetum pratense is most similar to E. arvense and E. palustre, except the branches are ascending and stiff in those species, not spreading or drooping as in E. pratense.
The cones of Equisetum pratense mature and shed spores in late spring.
Equisetum species reproduce sexually and asexually. Sexual reproduction is limited by ecological conditions. hygroscopic spores are produced, but they are short lived and germinate depending on humidity. Once germinated, the gametophyte produced by spores requires a recently exposed substrate to become established. Asexual reproduction is by rhizomatous growth which can be rapid in favorable moist and disturbed habitats. Reproduction also occurs by fragmentation of rhizomes and stems. Clones may spread rapidly, and since usually they are sterile, may establish characters indicating taxonomic differentiation.
Equisetum pratense is an incompletely circumpolar species (circumboreal, absent from Greenland). Outside of North America this species occurs in northern Eurasia to northeast China and Japan. In North America E. pratense occurs in all the Canadian provinces, in Alaska, and south central and eastern United States (Connecticut, Illinois, Iowa, Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New York, North Dakota, Vermont and Wisconsin). E. pratense occurs in most of Alaska, except for the coastal northern and southern portions. It occurs on both sides of the Alaska Range in Denali with similar frequency.
Throughout its North American range, Equisetum pratense occurs at altitudes 0-2000 m. It occurs at 134-1225 m in Denali, at an average of 490 m, with most occurrences between 300-1000 m. The majority of occurrences of meadow horsetail were on flat terrain (66%), with similar proportions on north and south facing slopes (16% and 13% respectively). The populations growing on inclines greater than 5 degrees were on mild slopes (10-20 degrees) and similar for both north and south facing-slopes. The cover of Equisetum pratense in measured plots decreases inversely with elevation.
Equisetum pratense grows on mesic to wet substrates, in sun or partial shade, in forests, woodlands, riverbanks, meadows, bog margins, and thickets. It is typically found where the substrate is derived from calcareous alluvial silts or sand (Botanical Society of the British Isles 2015).