FloraFinder.org
Home   About Us   Want to Help?   FAQ  
Searching   Image Use Biblio

Equisetum hyemale L.

 

Rough horsetail, common scouring rush

KingdomPlantaePlants, but not fungi, lichens, or algae
SubkingdomTracheobiontaVascular plants—plants with a “circulatory system” for delivering water and nutrients
DivisionEquisetophytaHorsetails, which date back to the Devonian era
ClassEquisetopsidaHorsetails, spore-bearing plants related to ferns
OrderEquisetalesLiving horsetails (most are extinct)
FamilyEquisetaceaeLiving horsetails
GenusEquisetumFrom equus, horse; and seta, bristle
SpecieshyemaleOf the winter, flowering in winter

About plant names...

The horsetail genus, Equisetum, is pretty much in a class by itself, a class with a very long history. A horsetail is not a flowering plant, and although it has a cone-like repro­ductive structure, it is not a conifer. It is not a rush or a grass either. Horsetails are grouped loosely with ferns, both of which predate flowering plants, because ferns also reproduce with spores and do not flower. But they aren’t ferns either. They are primitive vascular plants. Relatives of this group show up in the fossil record, dating back to the late Devonian period, about 375 million years ago.

Rough horsetails are found throughout North America and Eurasia. They favor areas that are reliably wet at least most of the year—wetlands, stream and river edges, seeps—forming colonies that are sometimes invasive.

Plants: Why is a plant that resembles an ancient crazy tall asparagus spear, or in cross-section, a tall green soda straw, called a horsetail? Because many members of this genus have a bushy, fine-grained branching structure that loosely resembles a horse’s tail. Rough horsetail, though, is most often a single unbranched, dark green stem, 7-86" (17-218 cm) tall. They are evergreen, and occur in colonies, spreading by underground roots. Each stem is punctuated by nodes surrounded by sheaths. The sheaths are actually tiny leaves, fused to the stem. The nodes provide structural support, a trick also evolved by grasses (including bamboo) and a number of flowering plants. In cross section, stems of rough horsetail are largely hollow, more so than in other horsetails. The stems feel rough to the touch.

So how can a flimsy-looking “soda straw” sometimes reach sometimes reach over 7 feet in height? Part of it is the nodes, which provide support. But the plant has another trick: it incorporates silica, tiny little glass balls of it, into its stem. It absorbs silicic acid, a mild acid present in small quanitites in the wet soil, and converts it to silica. This accounts for its unusual stiffness, the rough feel of the stems, and for its historical use for polishing or scouring metal and wood.

See Equisetum for a comparison chart.

Leaves: Technically, the tiny sheaths ringing the stem at regular intervals are groups of vestigial leaves, but they serve no purpose for the plant. Photosynthesis occurs in the stem. Each sheath has a black band at both the bottom and top, while smooth-stemmed horsetail has a black band only at the top. The sheaths are initially green, becoming light gray with age.

Fruits: Conelike structures at stem tips, called strobili, are ½-1" (1.3-2.5 cm), with sharp tips.

Online References:

Equisetum hyemale at the Missouri Botanical Garden

Equisetum hyemale on Wikipedia (Equisetaceae)

Equisetum hyemale on gobotany.nativeplanttrust.org

Equisetum hyemale on www.biologydiscussion.com

Equisetum hyemale on pubmed.ncbi.nlm.nih.gov (The role of silica in these plants)

References:

Cobb, Boughton, Farnsworth, Elizabeth & Lowe, Cheryl, Peterson Field Guides: A Field Guide to Ferns and Their Related Families of Northwestern and Central North America, Houghton Mifflin Company, 2005, p. 344

Equisetum hyemale (rough horsetail, common scouring rush)

The sheaths are black at both the bottom and top. · 12/12/2020 · Mitchell Field, Harpswell, Maine

Equisetum hyemale (rough horsetail, common scouring rush)

9/3/2020 · Mitchell Field, Harpswell, Maine
≈ 6 × 10" (16 × 24 cm)

Equisetum hyemale (rough horsetail, common scouring rush)

4/6/2010 · Nashua River Rail Trail, Groton, Mass­a­chu­setts
≈ 14 × 9" (35 × 23 cm) ID is uncertain

Equisetum hyemale description by Thomas H. Kent, last updated 1 Dec 2020.

© FloraFinder.org. All rights reserved.


 

Equisetum hyemale (rough horsetail, common scouring rush)

This is a little less than 1/4" in diameter. The valecular canals (green tubes encircling the stem) are much smaller than the central cavity. The stem is round: the oval shape resulted from a dull knife. · 12/12/2020 · Mitchell Field, Harpswell, Maine

Equisetum hyemale (rough horsetail, common scouring rush)

9/4/2013 · Amos Kendall Conservation Area, Dunstable, Mass­a­chu­setts
≈ 3 × 3" (8 × 8.1 cm) ID is uncertain

Equisetum hyemale (rough horsetail, common scouring rush)

The cone is typically 1/2-1", with a sharp tip. · 12/12/2020 · Mitchell Field, Harpswell, Maine

Equisetum hyemale (rough horsetail, common scouring rush)

8/31/2013 · Lewis Ginter Botanical Garden, Richmond, Virginia
≈ 16 × 24" (39 × 59 cm)

Equisetum hyemale (rough horsetail, common scouring rush)

9/3/2020 · Mitchell Field, Harpswell, Maine
≈ 4½ × 5" (11 × 13 cm)

Equisetum hyemale (rough horsetail, common scouring rush)

5/29/2010 · Maine Audubon Gilsland Farm Audubon Center, Falmouth, Maine
≈ 31 × 21" (78 × 52 cm)

Equisetum hyemale (rough horsetail, common scouring rush)

Sheaths near the base are darker, and bulge somewhat compared to the stems. The bulging often appears up further as well in older plants. · 12/12/2020 · Mitchell Field, Harpswell, Maine

Range: Zones 4-9:

About this map...