Ferns are often appreciated for their delicate foliage, but invasive species like Bracken fern can quickly become aggressive weeds. They spread rapidly through underground root systems, requiring complete and effective removal when they threaten native species or outgrow their welcome. This article details the most successful methods for eradicating stubborn fern infestations.
Non-Chemical Eradication Techniques
The most direct non-chemical approach involves physically digging out the plants with precision. Ferns propagate extensively via rhizomes, which are horizontal underground stems capable of sprouting new plants from small fragments. Successfully removing an established fern requires excavating the soil deeply to ensure the entire network of rhizomes is extracted, not just the visible fronds. Any remaining piece of the root system can quickly regenerate the infestation, requiring repeated monitoring.
When manually digging, trace the rhizomes horizontally, often found just beneath the soil surface, until the last branching point is found. Use a sharp spade or trowel to slice through the surrounding soil, minimizing the chance of breaking the rhizome into smaller, viable pieces. This meticulous process ensures the plant’s central energy source is completely compromised.
For larger patches, excluding sunlight offers a less labor-intensive removal method over a longer period. Smothering involves covering the fern patch with thick, opaque materials like black plastic sheeting or layers of cardboard topped with mulch. This technique starves the plants of the light required for photosynthesis, slowly killing the fronds and depleting the energy stored in the rhizomes. Depending on the growth density, this process can take several months to a full growing season for complete eradication.
Solarization uses clear plastic to trap solar energy, raising the soil temperature high enough to destroy plant material and dormant spores. This thermal process is effective at destroying the surface layer of the root system and significantly reducing the seed bank. The edges of the plastic must be securely buried in the soil to prevent heat escape and block air circulation.
Ferns typically flourish in moist, shady locations with acidic soil. Changing these conditions can suppress their growth and prevent re-establishment after removal. Improving soil drainage reduces water saturation, making the environment less hospitable to many fern species. Raising the soil’s pH slightly by incorporating dolomitic lime can also shift the balance away from the acidic conditions ferns prefer, inhibiting their vigor.
Targeting Ferns with Herbicides
Chemical control presents challenges because ferns possess a protective waxy layer, the cuticle, covering their fronds. This natural barrier repels water-based sprays, preventing non-specific contact herbicides from penetrating the leaf tissue effectively. For successful eradication, the chemical must be systemic, traveling through the vascular system to reach and destroy the deep-seated rhizome network.
Systemic herbicides containing active ingredients like glyphosate or triclopyr are the most effective tools against stubborn fern growth. Glyphosate is a broad-spectrum weed killer that interferes with an enzyme pathway necessary for plant growth. Triclopyr is often utilized in brush killer formulations and is effective on woody plants and various broadleaf weeds, including many types of ferns. These compounds must be absorbed by the foliage to move down into the rhizome’s energy reserves.
To overcome the fern’s waxy defense, adding a non-ionic surfactant is necessary during herbicide application. A surfactant is a chemical agent that reduces the surface tension of the spray solution, allowing droplets to spread out instead of beading up on the frond. This spreading action ensures maximum contact and absorption of the active ingredient into the plant’s vascular system. Without this step, the chemical simply runs off the foliage before it can take effect.
The timing of the herbicide application significantly influences its effectiveness against the entire plant structure. The chemical should be applied when the fern is actively growing, specifically when the plant is moving energy and nutrients toward its rhizomes for storage. Applying the herbicide during this period ensures the systemic chemical is efficiently translocated from the fronds down to the root system, maximizing the toxic effect. This usually corresponds to the mid-to-late summer months before the plant begins to senesce.
Because fern rhizomes store substantial energy reserves, a single herbicide application rarely achieves complete eradication of a mature patch. The initial treatment may kill visible fronds, but dormant buds on the rhizomes can sprout new growth weeks later. Therefore, a follow-up application is almost always required, typically repeated four to six weeks after the first sign of regrowth appears. Multiple treatments over a single growing season are often necessary to fully exhaust the plant’s underground reserves and ensure a complete kill.
Ensuring Complete Removal and Safety
Maximizing the efficacy of herbicide application begins with proper preparation of the fern material. Cutting the mature fronds back one to two days before spraying encourages the plant to rapidly send nutrients to the cut surfaces. The freshly cut stems and emerging young growth are often less waxy and more actively translocating resources, resulting in better uptake of the systemic herbicide.
When using chemical controls, nearby desirable plants must be protected from accidental exposure, primarily through spray drift. Physical barriers, such as cardboard or plastic sheeting, should be temporarily placed between the target fern and the surrounding vegetation during application. Alternatively, “glove wiping,” where the chemical is physically wiped onto the fronds with a chemical-resistant glove, minimizes the risk of airborne spray.
After the fern is dead, safe disposal of the plant material is necessary to prevent re-infestation, especially for species that spread via spores or resilient rhizome fragments. Dead fern debris should not be placed in compost piles, as this can inadvertently spread viable spores or allow rhizome pieces to regrow. Instead, the material should be bagged and disposed of with household waste. When handling chemicals, always wear appropriate personal protective equipment, including chemical-resistant gloves, protective eyewear, and long sleeves, and ensure adequate ventilation.