OregonFlora: Equisetum palustre

	Equisetum palustre
	marsh horsetail
Sheaths	rectangular, 5–10 mm, green; teeth 3–7 mm, persistent with a dark center and pale hyaline margins.
Aerial stems	annual, monomorphic; up to 80 cm tall, deeply grooved, green; ribs 5–10; central cavity less than 33% of the stem diameter.
Branches	in whorls; from the mid-region of the stem, numerous to sparse (rarely absent); ridges 4–6; first internode shorter than the sheath and not exserted.
Cones	pedunculate.
2n	=216.

	Equisetum palustre
Distribution	[WildflowerSearch map] [BONAP county map]
Discussion	Swamps, marshes. 0–1200 m. Casc, WV. Northern North America; Asia, Europe. Native. Damaged green stems of E. arvense can sometimes produce cones and resemble E. palustre. However, the latter differs from E. arvense in the size of its central cavity (greater than 33% stem diameter vs. less than 33% in E. arvense) and the first branch internode (shorter than sheath vs. longer than sheath in E. arvense).
Source	Flora of Oregon, volume 1, page 79 Duncan Thomas
Sibling taxa	E. arvense, E. fluviatile, E. hyemale, E. laevigatum, E. telmateia, E. variegatum
Web links	Local floras: BC, CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Equisetum palustre

marsh horsetail

Sheaths

rectangular, 5–10 mm, green;

teeth 3–7 mm, persistent with a dark center and pale hyaline margins.

Aerial stems

annual, monomorphic; up to 80 cm tall, deeply grooved, green;

ribs 5–10; central cavity less than 33% of the stem diameter.

Branches

in whorls; from the mid-region of the stem, numerous to sparse (rarely absent);

ridges 4–6; first internode shorter than the sheath and not exserted.

Cones

pedunculate.

=216.

Equisetum palustre

Distribution

[WildflowerSearch map]

[BONAP county map]

Discussion

Swamps, marshes. 0–1200 m. Casc, WV. Northern North America; Asia, Europe. Native.

Damaged green stems of E. arvense can sometimes produce cones and resemble E. palustre. However, the latter differs from E. arvense in the size of its central cavity (greater than 33% stem diameter vs. less than 33% in E. arvense) and the first branch internode (shorter than sheath vs. longer than sheath in E. arvense).

Source

Flora of Oregon, volume 1, page 79
Duncan Thomas

Sibling taxa

E. arvense, E. fluviatile, E. hyemale, E. laevigatum, E. telmateia, E. variegatum

Web links