“Horsetail” is a common name given to most plants under the Equisetum genus. Often perceived as living fossils, these wonderful species have ancestors that were widely distributed during prehistoric times. Now naturally present in all continents, apart from Antarctica, they tend to favor moist environments in temperate and tropical zones.
Rough horsetail (E. hyemale), marsh horsetail (E. palustre), water horsetail (E. fluviatile), and field horsetail (E. arvense) are just some of this genus’ most notable species. These are vascular plants, which produce spores instead of flowers to reproduce. Visually, they have striking shoots with specialized, tiny leaves. These are typically non-photosynthetic as they are arranged in whorls around evenly spaced nodes.
Throughout their native range, horsetails are vital members of wetland ecosystems. Cultivated as ornamentals for vibrant color, texture, and well-defined structure, horsetails are now common garden plants. Wherever they are found with properly managed colonies, they can bring a wealth of benefits to the garden. Interestingly, their chemical components have pharmacological uses too!
Physical Qualities of Equisetum
To fully comprehend the ecological impact of horsetails, it’s helpful to review some of their shared physical features. Of course, some species maintain an easily manageable mature height of just a few inches, whereas others can grow to massive lengths of 26 feet (8 meters). Regardless of their size at maturity, all horsetails share similar types of root structures.
Able to penetrate deep into the substrate, horsetail roots can grow to several times the length of their shoots. These have a knack for spreading quickly via a network of vigorous rhizomes in moist and rich soils. Due to their sturdy roots, even young horsetails are able to survive periodic floods and extended periods of submersion. For this reason, it may be difficult to control their spread.
Horsetails can maintain a fully terrestrial, emergent, or wholly aquatic habit. Mature, semi-aquatic species can usually tolerate being submerged in changing water levels. Their hollow, jointed stems are rough, rigid, and coated with silicates. The roots and shoots are usually tough enough to withstand mild herbicides and physical damage. Fortunately, other self-propagating crops may compete with horsetail stands and reduce their weed-like impact.
Environmental Benefits of Horsetails
When given proper growth conditions, coupled with responsible management, horsetails can be a favorable addition to gardens and larger ecological projects. These plants can survive in conditions where many other native species may struggle to become well-established. In damaged watersheds, horsetails can help re-purify resources and restore the natural balance of nutrients. Listed below are some of their most vital contributions to nature.
1) They create safe microhabitats for many small organisms
The emergent portion of horsetail shoots can provide protection, shelter, and nesting sites for a wide range of organisms. Submerged portions become mazes through which juvenile fish may hide and search for food. The exposed portions, which produce intricate patterns of hollow stems, can be safe havens for spiders, aquatic and terrestrial insects, and many other small invertebrates. Horsetails can help foster biodiversity by supporting the life stages of all sorts of animals. Their associated microhabitats support the food web, ensuring the longevity of fragile groups of amphibians and reptiles.
Additionally, shoreline patches of horsetails can facilitate the safe entry and exit of animals as they navigate between terrestrial and aquatic habitats. The flexible stems create dynamic pathways through which vulnerable organisms may access food and create their breeding grounds, all while minimizing the risk of injury and entrapment.
2) Their roots can help reduce erosion rates along the marginal zones of freshwater bodies
With root systems that can easily permeate through the deeper layers of soil, horsetail plants are vital for mitigating erosion and enhancing the stability of freshwater shorelines. Extensive and highly fibrous, their rhizomes bind the soil, preventing it from getting dislodged and washed away by stormwater and floods.
3) They aid in the aeration of terrestrial and aquatic substrates
By penetrating deep into dry or wet sediments, the roots of horsetail plants create channels through which gases can be exchanged between the substrate and the atmosphere. This process aids in oxygenating the substrate and preventing the dangerous buildup of anaerobic pathogens.
By improving gaseous exchange rates, the roots enhance the production of beneficial microbes, facilitate efficient nutrient cycling, and promote the overall health of their surrounding environment.
4) They serve as nutrient sources for many microbes and animals
Horsetails can serve as a source of nutrients for animals in a number of ways. First, the entire plant can be consumed by specialized herbivores, such as plant-eating fish and waterbirds. Some larger mammals, like caribou and bears, may also consume horsetails (though some Equisetum species are toxic to livestock) in the absence of other sources of nutrients.
Second, the surfaces of horsetail stems, which are characterized by segmented nodes, provide ample space where microbes can grow and thrive. These create important biofilms – an essential component of the diet of many juvenile aquatic organisms.
5) They accumulate and re-distribute minerals and nutrients more efficiently than many other wetland plants
Horsetail plants tend to outperform other beneficial wetland species when it comes to rapidly cycling nutrients and accumulating minerals. This is largely due to their deep roots, specialized shoot structures, and their unique physiology. With silica deposits strengthening their cell walls, these perennials can quickly take up and store minerals like silica and calcium. These become concentrated in their rhizomes and stems. Once these structures decompose or become consumed by other animals, the stored minerals are released.
The extensive rhizomes of horsetails allow them to access compounds that may be inaccessible to other wetland plants. By accumulating excess nutrients, they can aid in the filtration and purification of water features. Horsetails have high primary productivity rates and can act as nutrient pumps in wetland systems.
6) They contain phytochemicals that can act as natural fungicides and insecticides
Horsetail plants tend to be resistant to fungal diseases and pests because they produce high levels of silicates. Silica is useful in creating a physical barrier. It strengthens these species’ cell walls, making them less susceptible to damage and infectious diseases. It also improves their structural integrity and increases the effectiveness of their defense mechanisms.
Apart from being remarkably tough, the plant cells of horsetails contain many bioactive compounds. Rich in alkaloids and flavonoids, many of which function as pesticides, they can naturally inhibit the growth of fungi and repel harmful insects. They can thus be incorporated into a chemical-free approach to managing pests.
Ornamental & Functional Uses of Horsetails
As many horsetails can be cultivated as emergent plants, they are fantastic for naturalizing the borders of water features. They can help blur out the edges of garden and wildlife ponds, especially when their stems are long enough to be reflected onto the water’s surface. They are often used in whimsical garden setups with recycled containers. For example, an old bathtub can be filled with horsetails to create an unforgettable conversation piece!
The vertical shoots of horsetail plants can be used to create a natural screen or fence. Their rigid structure is especially eye-catching in Zen gardens, where they complement the fluidity of water and the rounded appearance of stones. The jointed stems have architectural elements that can add a modern or dramatic touch to either contemporary or minimalist arrangements. Sleek and upright, the stems elegantly contrast the features of leafy plants.
Apart from having ornamental uses, horsetail stems can also be useful in a more functional or industrial sense. Their shoots can be harvested and dried to create an organic scouring material. As a replacement for sandpaper, the dried stems are rough enough to smoothen the surfaces of metal pots and mugs. They also contain chemicals with anti-corrosive properties. These are useful in industrial processing facilities where rust may accumulate.
Can Horsetail Plants Be Harmful to the Environment?
Despite all of their merits as ecologically beneficial and pharmacologically important plants, horsetails may continue to be perceived in a negative light. Some species are simply so vigorous and hardy that they quickly become weeds. In the absence of other competitive native plants, massive colonies of horsetails can act as ecosystem engineers and make significant, sometimes undesirable, changes to wetlands. Equisetum arvense, in particular, is known for being a persistent and destructive weed.
Though horsetails are indeed difficult to eradicate once their stands are well-established, you can simply control their spread by growing them in dedicated pots and containers. Equisetum hyemale is usually a better option for ornamental gardens, though it can also escape cultivation. It would be prudent to avoid growing these plants if they are known for being troublesome in your area. Instead, opt for native species with less aggressive rates of spread.
