Invasive Ferns Taking Over the Garden: Control Strategies

A gardener battles ferns that have invaded their garden via underground runners. Over-the-counter herbicides haven't worked, and the ferns seem to thrive on them.

Understanding the Enemy

Many ferns (e.g., hay-scented fern, ostrich fern) spread aggressively by rhizomes. Once established, they are difficult to eradicate without harming desirable plants.

Step-by-Step Control

1. Temporarily remove desirable plants from the infested bed and pot them up.
2. Apply glyphosate (Roundup) to the fern foliage when actively growing. Multiple applications (2–3) spaced 2–3 weeks apart are usually needed.
3. Wait for complete kill before replanting. Glyphosate degrades quickly in soil, minimizing residual risk.
4. Monitor for regrowth and spot-treat immediately.

Why Glyphosate?

It translocates to the roots, killing the entire plant. It breaks down rapidly, allowing replanting within days. Avoid stronger, persistent herbicides that can contaminate soil long-term.

Alternative

If herbicide use is undesirable, smother the area with heavy cardboard and mulch for a full growing season, though this is less reliable for deep rhizomes.

Persistence is key—fern eradication is a marathon, not a sprint.