Overview

Comprehensive Description

Comments

This is my favorite Horsetail. It is less weedy and aggressive than Equisetum arvense (Field Horsetail) and Equisetum hyemale var. affine (Scouring Rush). Horsetails can be divided into two large groups
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Description

This perennial plant is ¾–3' tall and usually unbranched. Each plant consists of a central stem that has several cylindrical joints along its length; it is deciduous, dying down to the ground before the end of winter. Individual joints are a few inches long, up to 10 mm. in diameter, medium green, and glabrous; adjacent joints along the stem are interconnected by ring-like sheaths. The joints have 14-30 fine longitudinal ridges that are smooth to slightly rough-textured. The interior cavity of each joint is very large, extending across at least 70% of the joint's diameter. Individual sheaths are 1" long or less; they have 14-30 grayish black teeth (3 mm. or less in length) along their upper rims; except for the teeth of the uppermost sheath, these teeth are usually early-deciduous The small teeth are actually leaves that have been reduced to scales. The sheaths are mostly green, except for narrow bands of broken-off teeth along their upper rims that are whitish black. However, some older sheaths toward the bottom of the stem may become gray. The central stem rarely branches. However, an uncommon form of Smooth Horsetail, f. prolifera, produces narrow cylindrical branches in whorls along the upper one-half of the central stem. Each fertile shoot terminates in a spore-bearing cone at its apex. This spore-bearing cone is up to 1½" long, ovoid in shape, and usually rounded at the top, rather than apiculate (abruptly tapering to a short narrow point); it is either sessile or short-stalked. Immature cones are mostly olive green, but they may become yellow or pale red as they approach maturity. Each cone has several rows of angular sporangiophores (spore-bearing structures) that become increasing dark-colored and more elevated with age. The infertile shoots have the same appearance as the fertile shoots, except that they never produce spore-bearing cones. These cones are produced by fertile shoots during late spring or early summer for about 3-4 weeks. After releasing their spores to the wind, they become dark brown or black and gradually wither away. The root system consists of spreading rhizomes with secondary fibrous roots. Smooth Horsetail often forms clonal colonies of plants.
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Equisetum laevigatum is a rush-like perennial that rises from an underground rootstock structure. Normally the plant dies back over the winter, but some populations in the southwestern USA have individuals that can overwinter. The plant manifests jointed rough stems which are closed at the joints. The stem roughness are a result of inclusions of silica. Each stem exhibits longitudinal grooves that run vertically. Each joint has a sheath which is a minute pointed leaf-like structure. The species usually occurs along moist drainages in sandy and gravelly substrates.

The narrow green stems can attain heights ranging from 30 to 150 centimeters. The stems are generally unbranched and are capped with rounded cone-shaped sporangia. Stomata occur in single lines; moreover, the spherical spores of this species are green.

The appearance of this taxon is very similar to E. hyemale; moreover, The geometric arrangement of silica-tuberles at the shoot surface may be the best means to differentiate these two species.

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Distribution

National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

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Alta., B.C., Man., Ont., Que., Sask.; Ariz., Ark., Calif., Colo., Idaho, Ill., Ind., Iowa, Kans., Mich., Minn., Mo., Mont., Nebr., Nev., N.Mex., N.Dak., Ohio, Okla., Oreg., S.Dak., Tex., Utah, Wash., Wis., Wyo.; n Mexico including Baja California.
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Equisetum laevigatum is broadly distributed across North America in including the entire western USA and Great Plains. The southeastern USA and New England are excluded from the range. In Canada, the taxon is widely found in the entirety of the southern half of Canada.

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Physical Description

Morphology

Description

Aerial stems lasting less than a year, occasionally overwintering in the southwestern United States, usually unbranched, 20--150 cm; lines of stomates single; ridges 10--32. Sheaths green, elongate, 7--15 × 3--9 mm; teeth 10--32, articulate and usually shed early, leaving dark rim on sheath. Cone apex rounded to apiculate with blunt tip; spores green, spheric. 2 n =216.
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Diagnostic Description

Synonym

Equisetum funstonii A.A. Eaton, E. kansanum J.H. Schaffner
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Type Information

Holotype for Equisetum funstonii A.A. Eaton
Catalog Number: US 26007
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Verified from the card file of type specimens
Preparation: Pressed specimen
Collector(s): F. V. Coville & F. Funston
Locality: California, United States, North America
  • Holotype: Eaton, A. A. 1903. Fern Bull. 11: 10.
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Ecology

Habitat

Cones maturing in spring--early summer. Moist prairies, riverbanks, roadsides; 1530--3500m.
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Associations

Faunal Associations

Relatively few insects feed on horsetails (Equisetum spp.). Among them, the aphid Anoecia equiseti has been found to feed on the roots of Smooth Horsetail (Equisetum laevigatum); see Blackman & Eastop (2013). The larvae of several sawflies (Dolerus spp.) feed on the stems of horsetails, including Dolerus apricus and Dolerus tibialis conjugatus (Smith, 2006; Eastman, 2003). The larvae of a weevil, Grypus equiseti (Horsetail Weevil), develop within the stems, and the leafhopper Macrosteles borealis also feeds on these plants (Harms & Grodowitz, 2009; Eastman, 2003). Most of these insects are found primarily in boreal regions where horsetails are more common. Because horsetails often form dense colonies of clonal plants, they provide protective cover for small mammals, birds, and other vertebrate wildlife, otherwise they are little-used by these animals. The foliage is mildly poisonous, especially to horses, because it can cause thiamine deficiency. The foliage also contains high levels of silicate compounds; this makes it rather coarse and unpalatable to most mammalian herbivores, although moose occasionally feed on horsetails (Eastman, 2003). Photographic Location
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Molecular Biology and Genetics

Molecular Biology

Barcode data: Equisetum laevigatum

The following is a representative barcode sequence, the centroid of all available sequences for this species.


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Statistics of barcoding coverage: Equisetum laevigatum

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 4
Specimens with Barcodes: 6
Species With Barcodes: 1
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Conservation

Conservation Status

National NatureServe Conservation Status

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: N5 - Secure

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NatureServe Conservation Status

Rounded Global Status Rank: G5 - Secure

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Relevance to Humans and Ecosystems

Benefits

Cultivation

The preference is full sun, moist to mesic conditions, and poor soil containing gravel, clay, or sand (especially the latter). Smooth Horsetail will also grow in fertile soil, but it dislikes competition from taller plants. Both acidic and alkaline conditions are tolerated, as well as significant variations in moisture levels. Range & Habitat
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Notes

Comments

Schaffner named this species Equisetum kansanum because he applied the name E . laevigatum to what we now know is the hybrid E . × ferrissii . The coarser-stemmed, occasionally persistent forms in the southwestern United States have been called Equisetum funstonii .
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