meadow horsetail

(Equisetum pratense)

               
Conservation Status

IUCN Red List

not yet assessed

 

No image available

NatureServe

NNR - Unranked

SNR - Unranked

Minnesota

not listed

Wetland
Indicator
Status

Great Plains

FACW - Facultative wetland

Midwest

FACW - Facultative wetland

Northcentral & Northeast

FACW - Facultative wetland

Nativity

Native

 
Occurrence

Common

 
Habitat

Moist. Forests, woodlands, meadows, wetlands, streambanks, riverbanks, pond edges.

 
Sporulation

Late April to early July

 
Height

Sterile stems 6 to 20

Fertile stems 4 to 10

 

Identification

This is an erect, bushy perennial that rises on separate annual stems from a creeping underground stem (rhizome) and black, wiry, kinky roots. The rhizomes are deep, branched, slender, dull, and black. They have hairs only on the sheaths and do not have tubers. Separate fertile and vegetative (sterile) stems are produced in early spring at the same time and die back in the fall.

Sterile stems are erect, green, 6 to 20 tall, 1 32 to in diameter, and hollow. The central cavity is fairly large, to ½ the diameter of the stem, and is surrounded by a ring of 10 to 18 rather small vascular bundles. Each stem has 10 to 18 vertical ridges. Between the ridges each furrow has two broad, longitudinal bands of pores (stomates). It is smooth near the base, becoming very rough to the touch on the middle and upper stem with minute, long, sharp projections (spicules) on the ridges. The spicules are composed of mostly silica. The stem is segmented with nodes ¾ to 1½ apart. At the top of all but the uppermost segment is a green, appressed, ring-like, to 5 16 long sheath. The sheaths become progressively shorter as they ascend the stem. At the top rim of the sheath are 10 to 18 teeth, the number of teeth equaling the number of stem ridges. The teeth are 1 32 to 1 16 long; pale, thin, membranous, and transparent on the margins; and firm and dark in the center. They are free at the tip, fused only near the base, and are persistent, remaining after maturity.

A whorl of numerous slender branches is produced at middle and upper stem nodes. The branches are usually 3-angled, occasionally 4-angled, and solid. They usually spread horizontally, sometimes droop, and do not themselves branch. The first segment (internode) of each branch is 1 16 to 3 16long. At the lowermost node the first branch internode is shorter than the stem sheath above the node from which it extends. At the upper nodes the first branch internode is as long or longer than the adjacent stem sheath. Like the stems, the branches have segments with sheaths. The leaves are small, scale-like, fused together for part of their length, and appressed against the stem, forming a collar-like sheath around the nodes. These branch sheaths have usually 3, occasionally 4, triangular, acutely angled teeth, the number of teeth equaling the number of branch ridges. By mid-summer the branches may become as long as the stem.

Fertile stems are erect, brittle, 4 to 10 tall, and rare. They are fleshy, brown, and unbranched at first. They resemble an asparagus sprout but are brown because they lack chlorophyll. A solitary, spore-bearing cone is borne on a ¾ to 1 long stalk at the end of the stem. The cone is ¾ to 1 long, and, circular in cross-section, elliptic in long section, and rounded at the top. It is the same brownish color as the stem the stalk to which it is attached. It is covered with spore-bearing tubercles. The tubercles are darker brown to black with white markings. After shedding spores (sporulation) the cone drops off and the stem becomes green, a6t least at the nodes, and produces many short, spreading to drooping branches.

 
Similar
Species

Field horsetail (Equisetum arvense) fertile stems remain brown and unbranched and wither before the green sterile shoots appear. On sterile shoots, the central cavity is narrow, about ¼ the diameter of the stem. At the lowermost node the first branch internode is longer than the stem sheath above the node from which it extends. The branches are ascending. The teeth on stem sheaths are often fused together at the tip in pairs. The teeth on branch sheaths taper gradually to a narrow tip.


Distribution Distribution Map  

Sources: 2, 3, 4, 5, 7, 29, 30.


Comments

Taxonomy
There are 15 species of Equisetum, which is the only living genus in the family Equisetaceae, which is the only family in the order Equisetales, which is the only order in the class Equisetopsida. The history of Equisetum has been traced 300 million years to the Cretaceous period, and possibly to the Triassic period. That could make Equisetum the oldest living genus of vascular plants.

The genus Equisetum is divided into two subgenera, Equisetum and Hippochaete. field horsetail is one of the eight species in the subgenus Equisetum. Six of those eight species are found in North America. Five are found in Minnesota.

In this subgenus, the stems tend to be regularly branched, the branches appearing in a whorl at each stem node. This gives the plant the appearance of a horse’s tail, giving rise to the common name “horsetail”. The aerial stems of most of the species in this subgenus are annual.


Taxonomy

No Rank:

Moniliformopses (Equisetum + ferns)

 

Class:

Equisetopsida (horsetails)

 

Order:

Equisetales (horsetails)

 

Family:

Equisetaceae (horsetails)

 

Genus:

Equisetum (horsetails)

 

Subgenus:

Equisetum (horsetails)

 
Synonyms

 

 
Common
Names

meadow horsetail

shade horsetail

shady horsetail

   

 

 

 

 

 

 

 

 

 

Glossary

apiculate

Ending in a short, abrupt, flexible point.

 

internode

The portion of a stem between nodes.

 

node

The small swelling of the stem from which one or more leaves, branches, or buds originate.

 

rhizome

A horizontal, usually underground stem. It serves as a reproductive structure, producing roots below and shoots above at the nodes.

 

spicule

A minute, sharp, pointed, needle-like, epidermal projection.

 

sporulation

The process of forming spores.

 

stomate

A minute, epidermal pore, surrounded by two white guard cells, that allows the exchange of gasses and water vapor. The guard cells control the size of the opening. Plural: stomata.

 

succulent

Having thick leaves, stems, or roots that store water. Succulent tissues appear fleshy externally and juicy internally.

       

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