Equisetum fluviatile; The Water Horsetail is quit common on Iceland except for the highland regions. It typically grows in ditches and along bogs bordering rivers and lakes. This species never has side branches, like the much taller E. hyemale (which grows on much drier grounds) but unlike any other horsetail species on Iceland. It usually grows in dense, compact clusters of shoots. Another characteristic of this species is that the stems are hollow inside. The Icelandic name is Fergin. For an easy identification of similar Iceland horsetails I have the table below:
- E. arvense, field horsetail: the sporangial cones appear very early in spring on colorless stems before the green stems. The green stems typically have side branches pointed upwards.
- E. pratense, shady horsetail: characteristic are the horizontal, even drooping downwards of the lateral branches. The sporangial cones, however, appear on at first on top of unbranched main stems which form the lateral branches later as the spores mature.
- E. palustre: marsh horsetail: short side branches, terminal cones not pointed, about 13 dental points on stem-sheaths.
- E. fluviatile: water horsetail: no side branches, terminal cones not pointed, about 14 dental points on stem-sheaths.
- E. variegatum: variegated horsetail: no side branches, terminal cones pointed, about 5-8 dental points on stem-sheaths.
- E. hyemale: rough horsetail: no side branches, about 20 dental points on stem-sheath - but very tiny: the sheaths seems almost round. Much thicker stems than any other horsetail on Iceland.