The perennial weed Equisetum arvense, commonly known as Mare’s Tail or Field Horsetail, is a frustrating challenge for gardeners and land managers. This aggressive plant is a relic from the Carboniferous period, which speaks to its persistence and adaptability. Its resilience makes conventional weeding methods ineffective, often leading to rapid re-infestation. Successfully controlling Mare’s Tail requires a strategic, multi-pronged approach that targets the plant’s unique biological defenses and extensive root system.
The Biology That Makes Mare’s Tail Difficult to Eliminate
Mare’s Tail is difficult to eradicate due to its deep, complex underground structure. It uses an extensive network of horizontal rhizomes that can penetrate the soil to depths of six to ten feet, sometimes reaching twenty feet. These rhizomes store significant energy reserves and bear small tubers, allowing the weed to regrow rapidly even after removing all visible green stems. Disturbing the soil, such as through tilling, often fragments the rhizomes, allowing each small piece to sprout a new, independent plant.
The plant’s second defense is the high concentration of silica embedded in its cell walls. This siliceous composition forms a waxy, protective cuticle that severely limits the absorption of conventional herbicides. Mare’s Tail also exhibits dimorphism, producing two distinct stem types. In early spring, non-photosynthetic, light brown stems emerge to release spores before withering away. These are followed by the familiar, bushy, green sterile stems that perform photosynthesis and feed the massive underground system throughout the growing season.
Physical and Cultural Control Methods
Non-chemical strategies focus on exhausting the deep rhizome system by stripping the plant of its photosynthetic capacity. The most effective method involves consistently removing the sterile green stems every two weeks throughout the entire growing season. This cutting prevents the plant from replenishing stored carbohydrates, slowly starving the weed over a period of three to four years. A single season of cutting is not sufficient for complete control.
Smothering with Barriers
An alternative physical method is using light-excluding barriers to smother the infestation. Thick, opaque sheeting, such as heavy-duty black plastic, blocks sunlight entirely. This process must be maintained for a minimum of two full growing seasons, as the rhizomes are capable of surviving for extended periods without light. While landscape fabric can be used, thick plastic is more reliable because aggressive rhizomes often find ways around edges or through small holes.
Cultural Control
Cultural control involves altering the environment to make it less favorable for Mare’s Tail, which often thrives in compacted or poorly drained soils. Improving soil structure through aeration and the incorporation of organic material reduces the plant’s vigor. While this will not eradicate a severe infestation alone, creating a dense, healthy lawn or groundcover provides competition that naturally suppresses the weed’s ability to establish and spread.
Strategic Chemical Eradication Techniques
Chemical control requires specialized application to overcome the plant’s natural resistance. The high silica content and waxy cuticle necessitate a pre-treatment step for effective herbicide penetration. This involves physically damaging the plant by crushing, bruising, or scoring the stems with a garden tool immediately before spraying. This mechanical damage breaches the protective outer layer, creating pathways for the chemical to enter and translocate down to the rhizomes.
The most effective compounds are systemic herbicides designed to travel throughout the plant’s vascular system and into the roots. Standard glyphosate formulations show limited success and often result in rapid regrowth. Better results are achieved using products containing active ingredients like MCPA, triclopyr, or specific glyphosate formulations intended for deep-rooted weeds. Amitrole is another powerful, non-selective option that provides high efficacy, though its use is generally restricted to non-crop areas.
Timing is crucial, as the plant must be actively growing to transport the chemical effectively. Application is most effective in late summer or early fall when the plant moves energy and nutrients down to the rhizomes in preparation for winter dormancy. The addition of a nonionic surfactant or sticking agent (adjuvant) is highly recommended to improve adhesion and enhance penetration on the waxy stems. Multiple, successive applications are required for long-term control.
Long-Term Site Management and Prevention
Mare’s Tail requires continuous long-term management due to the persistence of its deep-seated rhizomes, even after a successful initial campaign. Vigilant monitoring is necessary, especially in early spring, to catch new shoots emerging from surviving fragments. These new shoots must be spot-treated immediately to prevent them from establishing the extensive underground system all over again.
Preventing Lateral Spread
If an infestation borders an unmanaged area or a neighbor’s property, a physical barrier may be necessary to prevent re-infestation via lateral rhizome spread. Since the roots grow many feet deep, a deep root barrier installed vertically acts as a permanent containment measure. This barrier should be non-porous, thick plastic or metal sheeting that extends down several feet to block the horizontal movement of the rhizomes.
Maintaining the health of the surrounding soil and existing plant life is a final preventative measure. A dense, vigorous stand of turfgrass or robust groundcover will outcompete any emerging Mare’s Tail shoots. Focusing on good soil drainage and ensuring desirable plants are thriving makes the environment naturally resistant to re-establishment.