Equisetum palustre
Equisetum x ferrissii
marsh horsetail
Ferriss' horsetail
rectangular, 5–10 mm, green;
teeth 3–7 mm, persistent with a dark center and pale hyaline margins.
rectangular; up to 6 × 12 mm, green, with single dark terminal band around the bases of teeth or 2 dark bands and a pale section between bands;
teeth articulated with an early-deciduous blade and persistent dark incurved bases.
annual, monomorphic; up to 80 cm tall, deeply grooved, green;
ribs 5–10; central cavity less than 33% of the stem diameter.
persisting over winter, usually unbranched; to 50 cm tall, green; central cavity approximately 75% of stem diameter.
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.
usually absent; where present ascending; hollow; and resembling narrow main stems.
pedunculate.
subsessile or shortly pedunculate; pale and misshapen; spores infertile.
=216.
Equisetum palustre
Equisetum x ferrissii
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).
Wet places, sandy shores, roadsides. 0–2000 m. BW, Casc, Col, ECas, Sisk, WV. CA, ID, NV, WA; throughout North America. Native.
This species is a hybrid between E. hyemale var. affine and E. laevigatum. It is usually found where both parents occur. The species is sterile but persists by vegetative growth.
Duncan Thomas
Duncan Thomas
- 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
