Asparagus fern is a common ornamental plant that has become a widespread invasive species in many temperate and subtropical regions. Despite its delicate appearance, this plant is notoriously difficult to eliminate once established. Its aggressive nature allows it to smother native ground covers and understory plants, forming dense thickets that disrupt local ecosystems. Effectively removing this plant requires a multi-faceted approach that addresses both its extensive root system and its prolific seed production.
Why Asparagus Fern Is Difficult to Eradicate
The persistence of the asparagus fern is directly linked to its robust, specialized underground structure. The plant develops a dense mat of fibrous roots and numerous fleshy, white, bulbous tubers. These tubers function as massive storage organs, packed with water and carbohydrates, allowing the plant to survive prolonged drought and recover quickly after the foliage is cut back or damaged.
Because of this stored energy, simply pulling the top growth will not kill the plant, as it has the fuel necessary for rapid regrowth from the crown. Mature plants produce small, round berries that ripen to a glossy red, each containing one to three seeds. Birds and other animals disperse these viable seeds over long distances. Seeds can also be spread by water or through the improper disposal of garden waste containing the tubers, leading to constant establishment of new plants.
Mechanical and Cultural Removal Strategies
For smaller infestations or areas where chemical use is restricted, manual removal is the most reliable method. The process begins by cutting back the dense, wiry stems to expose the crown at the soil surface; wear thick gloves to protect against the small, sharp spines on the stems. Once the crown is visible, use a shovel or trowel to dig out the entire root ball, ensuring every tuber is extracted.
The removal must be meticulous, as any small segment of the rhizome or crown left behind can lead to regrowth. For very large, dense patches, cultural control methods like smothering can be effective over time. Applying a thick layer of organic mulch (3 to 4 inches deep) or using solarization with clear plastic sheeting can suppress new growth. This blocks sunlight, forcing the plant to deplete the energy reserves within the tubers without the ability to replenish them.
Chemical Control Options and Application
Chemical control is often necessary for large, established infestations too extensive for manual digging. Systemic herbicides, which are absorbed by the foliage and translocated down to the roots and tubers, are the only effective chemical option against the plant’s storage organs. Contact herbicides are ineffective because they only burn the foliage, leaving the underground tubers unharmed and ready to sprout new growth.
Glyphosate is frequently recommended for its systemic action, as it moves throughout the plant to kill the entire structure. The most effective application technique is the cut-stump method, which minimizes herbicide contact with surrounding desirable plants. First, cut the stems close to the ground, and immediately (within 15 seconds) apply a concentrated glyphosate solution directly to the freshly cut surfaces still attached to the ground. This timing is important because the plant quickly seals the wound, preventing herbicide uptake. Foliar spraying can also be used on actively growing plants, but the waxy cladodes provide a small surface area for absorption, often requiring multiple applications.
Post-Removal Management to Prevent Recurrence
Eradication is never a one-time event with asparagus fern; vigilance is necessary to manage the soil seed bank and any missed root fragments. The removed plant material, particularly the tubers and red berries, must be disposed of properly to avoid accidental spread. Never place these materials in a compost pile or green waste bin, as the seeds remain viable for up to three years, and the tubers can regrow. Instead, bag the material securely and dispose of it in general waste collection.
The cleared area must be monitored closely for new seedlings, which will emerge from the soil seed bank for months or even years following the initial removal. These new plants are easiest to remove by hand-pulling when they are very small, before their own tubers develop. Establishing a dense, competitive ground cover, such as a native plant species, is a sound long-term strategy, as it will suppress the germination and growth of new asparagus fern seedlings by limiting light and nutrient availability. Follow-up inspections and repeat treatments—either manual or chemical—are required to achieve complete and lasting control.