Equisetum fluviatile

This native perennial plant is about 1½–3' long. It consists of a central stem that is erect or semi-erect; this stem often has whorls of 2-6 branchlets along the upper half of its length, otherwise it is unbranched. The central stem has about 15-25 fine ridges along its length; it is green to dark green. The stem diameter is up to 1/3" across; it has a very large interior cavity that spans at least 80% of the diameter. The central stem consists of several overlapping joints. Each joint is several inches long; its apex consists of an appressed ring-like sheath, from which the base of the next joint develops. This sheath is about ¾" in length and green to brownish green; it is often dark brown or black at the base, while its upper rim has about 18 tiny teeth that are dark brown or black. However, the sheaths and their teeth become whitish grey as they age. The jointed branchlets have an appearance that is similar to the central stem, except that they are smaller. These branchlets usually spread upward, rather than droop downward; unlike the central stem, they are always unbranched. The branchlets are hollow and they span a few inches in length. Each fertile shoot produces a spore-bearing cone that is about 1" long; this cone is usually rounded at the top and it occurs on a short stalk. Infertile shoots are similar to fertile shoots, except they lack spore-bearing cones; both types of shoots are deciduous, rather than evergreen. The spore-bearing cones are produced during late spring to early summer. After releasing their spores, they gradually wither away. The root system consists of extensive rhizomes and fibrous roots. This plant often forms vegetative colonies.

The webmaster was surprised to find several colonies of this wetland plant growing on the gravelly embankment of a railroad. For some reason, Horsetails often do this, even though this type of habitat is supposed to be too dry for them. Water Horsetail is a rather slender and medium-sized Equisetum sp. that produces small whorls of branchlets in the upper half of its stems. It is smaller than Equisetum hyemale var. affine (Scouring Rush), but larger than Equisetum arvense (Field Horsetail). Field Horsetail also produces whorls of branchlets along its stems, but its branchlets are more abundant and they eventually become almost as long as the central stems. The branchlets of Water Horsetail are less abundant and they are always much shorter than the central stems. Water Horsetail resembles Equisetum palustre (Marsh Horsetail), Equisetum pratense (Meadow Horsetail) and Equisetum sylvaticum (Woodland Horsetail), but its stems are more hollow. The interior cavity of these latter species spans less than 50% of the diameter of their stems.

Water Horsetail occurs occasionally in the northern half of Illinois, but it is absent in the southern half of the state. Habitats include marshes, swamps, bogs, edges of ponds and creeks, sloughs, ditches, and railroad embankments (including the gravel ballast). This species prefers more aquatic habitats than most Equisetum spp. (Horsetails).

Equisetum limosum L.:
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Equisetum fluviatile L.:
Aleutian Isl (Oceania)
Canada (North America)
Japan (Asia)
Mongolia (Asia)
Russian Federation (Asia)
South Korea (Asia)
China (Asia)
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Alaska including the Aleutian Islands, Conn., Del., D.C., Idaho, Ill., Ind., Iowa, Maine, Md., Mass., Mich., Minn., Mont., Nebr., N.H., N.J., N.Y., N.Dak., Ohio, Oreg., Pa., R.I., S.Dak., Vt., Va., Wash., W.Va., Wis., Wyo.; Eurasia s to n Italy, China, Korea, Japan.

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

United States

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

Global Range: Ranges from Labrador to Alaska south to Virginia, Illinois, NW Wyoming, N Idaho, and Washington.

Aerial stems monomorphic, green, unbranched or branched, 35--115 cm; hollow center large, to 9/10 stem diam.; vallecular canals absent. Sheaths squarish in face view, ca. 4--10 × 4--10 mm; teeth black, occasionally with narrow white border, 12--24, narrow, 2--3 mm. Branches when present only from midstem nodes, spreading, hollow, ridges 4--6, valleys rounded; 1st internode of each branch shorter than subtending stem sheath; sheath teeth narrow. 2 n =216.

Equisetum limosum Linnaeus

Water Horsetail occurs occasionally in the northern half of Illinois, but it is absent in the southern half of the state. Habitats include marshes, swamps, bogs, edges of ponds and creeks, sloughs, ditches, and railroad embankments (including the gravel ballast). This species prefers more aquatic habitats than most Equisetum spp. (Horsetails).

Cones maturing in summer. Standing in water, in ponds, ditches, marshes, swales; 0--1500m.

The value of Equisetum spp. (Horsetails) to wildlife is limited. Because of the dense colonies that they often form, Horsetails provide cover for wetland birds and small mammals. Because stems of Horsetails contain high levels of silica and can cause thiamine-deficiency, they are rarely eaten by most mammalian herbivores. Moose is an exception, but this animal doesn't occur in Illinois.

In Great Britain and/or Ireland:
Foodplant / saprobe
seriate or widely scattered, covered pycnidium of Ascochyta coelomycetous anamorph of Ascochyta equiseti is saprobic on locally bleached, dead, dry stem of Equisetum fluviatile
Remarks: season: 2-4
Other: major host/prey

Foodplant / feeds on
Bagous collignensis feeds on Equisetum fluviatile

Plant / resting place / within
pupa of Bagous lutulentus may be found in stem (upper) of Equisetum fluviatile

Foodplant / open feeder
larva of Dolerus cothurnatus grazes on frond of Equisetum fluviatile

Foodplant / saprobe
scattered apothecium of Gorgoniceps boltonii is saprobic on dead stem of Equisetum fluviatile
Remarks: season: 4-5

Foodplant / saprobe
short-stalked apothecium of Hymenoscyphus equisetinus is saprobic on dead stem of Equisetum fluviatile

Foodplant / saprobe
long-stalked apothecium of Hymenoscyphus pileatus is saprobic on dead stem of Equisetum fluviatile
Remarks: season: 10-11

Foodplant / saprobe
apothecium of Hymenoscyphus rhodoleucus is saprobic on dead stem of Equisetum fluviatile
Remarks: season: 4-9

Foodplant / miner
larva of Liriomyza virgo mines stem of Equisetum fluviatile
Other: sole host/prey

Foodplant / saprobe
short-stalked apothecium of Psilachnum inquilinum is saprobic on black, dead stem (base) of Equisetum fluviatile
Remarks: season: 3-10

Foodplant / saprobe
loosely gregarious, covered, black pycnidium of Rhabdospora coelomycetous anamorph of Rhabdospora detospora is saprobic on stem of Equisetum fluviatile
Remarks: season: 4

Foodplant / saprobe
immersed pycnidium of Stagonospora coelomycetous anamorph of Stagonospora equiseti is saprobic on dead stem of Equisetum fluviatile
Remarks: season: 8

Foodplant / saprobe
scattered, immersed, globose, brown pycnidium of Stagonospora coelomycetous anamorph of Stagonospora equisetina is saprobic on dead stem of Equisetum fluviatile
Remarks: season: 9

Foodplant / saprobe
sometimes in rows acervulus of Titaeospora coelomycetous anamorph of Titaeospora equiseti is saprobic on dying, locally reddish-brown stained stem of Equisetum fluviatile
Remarks: season: 3-4

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 7
Specimens with Barcodes: 17
Species With Barcodes: 1

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: NNR - Unranked

Rounded Global Status Rank: G5 - Secure

The preference is full to partial sun and wet to moist conditions. Different kinds of soil are tolerated, including those containing sand, gravel, and sphagnum moss. The pH of the soil can be acidic or alkaline. This plant often grows in shallow water, although it can tolerate surprisingly dry situations as well.