Climbing asparagus fern (Asparagus setaceus, A. plumosus, A. africanus) is common in gardens and natural areas. Despite its common name, it is not a true fern but belongs to the Asparagaceae family. Its delicate, fern-like foliage gives rise to common names like lace fern or ferny asparagus.
Identifying Climbing Asparagus Fern
Identifying climbing asparagus fern: Its “leaves” are actually modified stems called cladodes, which are fine, needle-like, dark green structures. These appear in clusters of 8-15, generally 4-7 mm long and 0.5 mm wide, arranged in flat sprays or spirals. The plant produces small, inconspicuous greenish to white, bell-shaped flowers, usually 5-7 mm wide, appearing individually or in pairs.
After flowering, small, rounded berries develop, transitioning from green to black or orange-red when ripe. These berries are 4-5 mm in diameter and contain one to three seeds. It is a scrambling or vining perennial with wiry stems that can climb over other vegetation, reaching several meters in length. Some species have scattered curved spines along their stems, while others are thornless.
Understanding Its Growth and Spread
Climbing asparagus fern establishes quickly in various environments. Its vining stems can extend up to 5-12 meters, scrambling over ground cover or climbing into tree canopies or structures. It propagates effectively through both seeds and underground structures. Seeds, produced in large quantities (up to 21,000 per plant), are primarily dispersed by birds that consume the berries.
The plant also spreads through underground rhizomes and tubers, modified stems and swollen roots that store energy, allowing vigorous regrowth. These tubers enable the plant to resprout even after disturbances. Root fragments spread through dumped green waste, deliberate planting, or contaminated machinery lead to new infestations. The plant tolerates heavy shade, various soil types, and a range of temperatures, thriving in moist, fertile conditions with adequate support for climbing.
Invasive Status and Environmental Impact
Climbing asparagus fern is an invasive species in many warm, subtropical, and tropical climates. Classified as a weed of national significance in areas like Australia, its aggressive growth allows it to outcompete native flora by forming dense monocultures, reducing local biodiversity.
The dense mats formed by its underground roots and tubers prevent the germination and establishment of other plants. Its vining habit allows it to climb and smother existing vegetation, including trees, reducing food and habitat for native wildlife. Its weight and smothering effect can even cause tree branches to fall. This invasion alters ecosystems by changing light levels and displacing vulnerable native species, including epiphytes. In Australia, it is a significant environmental weed in Queensland and New South Wales, and its sale or distribution is prohibited in New Zealand under the National Pest Plant Accord.
Managing and Controlling Climbing Asparagus Fern
Managing climbing asparagus fern focuses on control and removal. For small infestations, manual removal can be effective, requiring diligent effort to extract all underground tubers and rhizomes. Any remaining root material can lead to regrowth, so digging out the entire crown, its central growing point, is crucial. Dispose of plant material responsibly to prevent further spread, since discarded fragments can re-establish. Composting is an option, but ensure no fruit is present and turn the material regularly, covering it to aid decomposition and prevent regrowth.
Chemical control methods, particularly herbicides, are used for larger infestations. Glyphosate is a commonly recommended herbicide, applied through spot spraying, cut stump, or basal bark treatment. When applying herbicides, read product labels carefully for instructions, application rates, and safety precautions. To minimize harm to desirable plants, consider cutting taller plants back to 30-60 cm before spraying the remaining lower vegetation. This reduces herbicide use and allows targeted application.
Ongoing monitoring and follow-up treatments are essential, as plants can resprout from residual tubers or new seedlings can emerge from the seed bank. Repeated efforts, potentially every 6 months, are necessary for successful long-term management.