Herbarium: Medicinal Plants as Information

Equisetum laevigatum: History, Collection, Naming, and Medicinal Properties

Equisetum laevigatum was collected in the Santa Monica Mountains, Los Angeles, California by sandy banks near a stream. This specimen was collected on May 7, 1998 and recorded at the UCLA Herbarium. This is a frequent collection with 11K plants collected according to CCH2 records. Equisetum laevigatum, also known as Smooth Horsetail, is often pictured as brown throughout literature although it is seen as green throughout nature. This plant has two main components: the long stem which makes up the majority of the plant and its acorn-like cone at the top. The stem is green, which can grow 2 to 4 feet tall and 1 to 6 feet wide and can be fertile or sterile depending on the presence or absence of a cone. Moreover, the stem is thick and is circled by black teethed “leaves” every 2 to 6 inches. According to Southwest Colorado Wildflowers’s website, Equisetaceae, the specimens scientific family, are the sole survivors of a line of plants going back three hundred million years and gave rise to many of North America's coal deposits. E. laevigatum, or smooth horsetail or scouring rush, is widespread throughout North America, Canada, and Southern Mexico. In the UCLA Botanical Garden, another species from the Equisetecae family is found. Equisetum hyemale, known as Tall Scouring Rush, is very similar to Equisetum laevigatum. It also has black teeth but has a black band around the base of its gray sheath and tip.

The Materia Medica covering the Equisetum species dates back to the 1800s as documented in the Wellcome Collection. Based on the other works of John Curtis found in the Wellcome Collection, this image of Equisetum must be part of a compilation of plants and their associated insects during the 1830s. It may have been used as an educational material or material for plant/insect enthusiasts. Only the upper half of the plant is drawn but we notice that the plant is brown versus green, which is how it is depicted in most internet searches. Moreover, the plant appears hard, yet brittle and dry. It is important to note the beetle next to the plant because the plant's structure looks similar to the anatomy of the beetle. For example, the plant has multiple sections along its stem which mimics that of a beetle’s leg. Additionally, this plant has an acorn-like opening at the top that seems to spread out and may possibly have nutrients for insects. Another E. laevigatum specimen was also collected in the Missouri Botanical Garden on October 17 1976 and recorded at the Missouri Botanical Garden Herbarium. This specimen was collected by George Englemann in August 1942 and annotated 15 years later in 1957 by Emily L. Hartman. Some of the distinct characteristics observed in the aforementioned Materia Medica as well as the specimen in the UCLA Herbarium and Botanical Garden are also seen in this record. The curved and segmented stem is particularly notable in this image. However, this specimen lacks the leaves seen in the UCLA Herbarium record, indicating it is a fertile stem.

This plant's is common name, smooth horsetail, was inspired by some key characteristics. For example, the long and branched stems fan out from the root-like hairs of a horse’s tail. The long thick stems are further intertwined with shorter thin stems making the plant denser. The root is thick yet flexible which parallels the tail of a horse: it is usually thicker closer to the rear end and flexible for mobility. Furthermore, the segmentation of this species stems give it a curved stature similar to a tail's anatomy, especially in the Herbarium records. This specimen could also be deemed multi-purpose, much like the hair of a horse's tail. This specimen is not only known for its medicinal uses, but was also once used to scour and clean surfaces. The Equisetum stems also contain high concentrations of silica, which has benefits for hair, skin, and nails. While many specimens in the Equisetacea family are referred to as Horsetail, Equisetum Laevigatum is specified with the adjective “smooth.” This is likely due to the smooth nature of the stem in between its teethed ridges. 

The medicinal uses of Horsetail date back to ancient Roman and Greek times. The smooth horsetail was used as a treatment for various ailments. Traditionally, it was used as a diuretic. Horsetail helps the body get rid of excess sodium and water, and it stimulates the kidneys to release sodium into the urine. Eventually, increasing urine output. Aside from being a diuretic, it has antioxidant properties that could help prevent cell damage by protecting against free radicals. Additionally, smooth horsetail was used as a contraceptive; and as a treatment for hemorrhoids, high blood pressure, backaches, and colds. Traditionally, Equisetum laevigatum comes in liquid form (horsetail infused water). Currently, it can also be found in capsule form. Topically, it was used to treat allergic reactions from poison ivy.

WORKS CITED

Curtis, John. 1830. “A Horsetail Plant (Equisetum Species) with an Associated Beetle and Its Anatomical Segments. Coloured Etching, c. 1830.” Wellcome Collection. August 1, 1830. https://wellcomecollection.org/works/r9tueb3s.
Mount Sinai New York. n.d. “Horsetail Information.” Mount Sinai Health System. Accessed March 7, 2022. https://www.mountsinai.org/health-library/herb/horsetail.
SEINet Portal Network. n.d. “Equisetum Laevigatum A. Braun.” SEINet Portal Network. Accessed March 7, 2022. https://swbiodiversity.org/seinet/taxa/index.php?taxon=1980.
Southwest Colorado Wildflowers. n.d. “Equisetum Laevigatum.” Accessed March 7, 2022. https://www.swcoloradowildflowers.com/Fern%20Enlarged%20Photo%20Pages/equisetum%20laevigatum.htm.
Tropicos.org. n.d. “Engelmann - s.n. - United States.” Missouri Botanical Garden. Accessed March 7, 2022. http://legacy.tropicos.org/Image/14796.

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