Dwarf Scouring Rush Facts, Care, & Hardiness (Equisetum scirpoides)
Dwarf scouring rush, also called dwarf horsetail, is a hardy grass plant distantly related to ferns. This evergreen rush has a 2.5-20cm (1 to 8 in) tall stem that twists and bends into gnarly patches. These stems are only branched at the base so they appear as singular stalks. Stems are about 1mm (0.04 in) in diameter and have a brown and white banding pattern caused by the pseudo-leaves or “teeth.”
These peculiar-looking plants grow in saturated soil or shallow waters of marshland, bogs, and floodplains of coniferous forests and can survive both high altitudes and subarctic climates. The dwarf scouring rush is native to northern North America and many parts of Eurasia, including alpine (above the tree line) and montane (along the mountain slope) environments.
The dwarf scouring rush is the smallest in its family of horsetail, Equisetum. The family name, equus meaning horse and seta meaning bristle, refers to the coarse, dark roots that seemingly resemble a horse’s tail. This particular species receives its common name, the scouring rush, for its use as an abrasive. The dwarf scouring rush has high silicon content, a hard crystalline element that makes up gritty materials such as concrete, mortar, and ceramics. As a result, this rush was used like sandpaper and to clean pots and pans throughout history. The family Equisetum is considered a living fossil as it is the only surviving member of the horsetail genus that dates back 350 million years ago.
Dwarf Scouring Rush Growth & Hardiness
The dwarf scouring rush grows in dense colonies that can spread around 60 cm (24 in) across and reach heights up to 20 cm (8 in). These plants, like many other grasses, have inconspicuous blooms that look like dark rings along the stalk. Like ferns, the dwarf horsetail produces spores during summer.
Dwarf scouring rush stalks will die at the beginning of winter and their roots will remain dormant. During springtime, the plant will regrow—a cycle that can last over 10 years. This hardy plant is viable in USDA zones 4 to 9, meaning that it can survive areas with low temperatures from -34°C (-30°F) to -1.1°C (30°F). These plants are considered low maintenance and grow enthusiastically given the proper environment. The dwarf scouring rush prefers moist soil with an acidic to mildly acidic pH. This rush prefers full sun to partial shade, but it can also tolerate full shade for periods of time.
How to Plant Dwarf Scouring Rush (Dwarf Horsetail)
Seeds and spores are rarely ever used to propagate plants, so you will likely start your dwarf scouring rush with roots or a small plant. Because of their propensity to roam far from the original planting place, it is suggested that you plant dwarf scouring rush in a separate container. This rush does well with ample space so an 11 cm (4 in) basket, 7.5 liter (2 gallon) pot, medium planting bag, or 25 cm (10 in) floating planter is recommended for one plant. The dwarf scouring rush does not do well when submerged in water. It prefers damp soil but can tolerate water depths of up to 5cm (2 in) above its roots. Dwarf scouring rush is tolerant of many soil types as long as it remains continuously moist.
How to Care for Dwarf Scouring Rush (Dwarf Horsetail)
The dwarf scouring rush is particularly low maintenance and only requires the soil to remain constantly wet. Upkeep is straightforward: any wilted or diseased looking stalks should be trimmed immediately from your dwarf scouring rush down to the soil line.
In the fall, the plant stalks will turn brown and undergo its natural die-off. It is helpful to trim these brown stems down to the roots in preparation for winter and to promote regrowth in the spring. This rush is winter hardy and can remain outside during some of the harshest of winters.
Is Dwarf Scouring Rush Toxic, Poisonous or Invasive?
Dwarf scouring rush does not appear to be invasive, although there is limited data on this plant. In fact, some botanists believe it may be threatened or endangered in its native environment in certain areas like the U.S. state of Connecticut. However, the horsetail family is notorious for spreading quickly and being resistant to removal. This species has countless dense, thin roots, which can regenerate entire plants and make manual extraction nearly impossible. Once the dwarf scouring rush has taken hold in an area, it can spread rapidly until it reaches a physical barrier. Although no information exists on dwarf scouring rush dominating a wild environment, some homeowners have undergone the laborious process of extracting it from their gardens after not properly containing the initial plant.
The dwarf scouring rush is toxic to horses if consumed in excess of 1.8 kg (4 lbs) per day. It is not known why the horsetail rush family is toxic to horses, but some scientists believe that it contains a high level of an enzyme that breaks down vitamin B1, an essential compound needed to derive energy from food. Usually, this poisoning only happens when dried scouring rush is mixed in with hay, as the live plant is less appetizing.
Will Koi & Pond Fish Eat Dwarf Scouring Rush?
There is little information on whether fish or other animals are affected by dwarf scouring rush toxicity. However, since vitamin B1 is required for all living things, the breakdown of large quantities of this molecule is expected to be dangerous to a wide variety of animals.