Ferns exhibit a diverse range of growth habits, with some species displaying a unique method of expansion through structures commonly referred to as runners. These specialized stems allow certain ferns to spread horizontally, colonizing new areas and forming new plants without relying on spores. Understanding this fascinating aspect of fern biology provides insight into their natural propagation strategies. This distinctive characteristic not only contributes to their spread in natural environments but also offers a straightforward method for gardeners to propagate new fern specimens.
What Are Fern Runners?
Fern runners are botanically known as stolons, which are horizontal stems that grow along the soil surface. These slender, creeping stems emerge from the main fern plant, extending outwards and periodically producing new plantlets at various points along their length. Each plantlet develops its own root system and fronds, eventually becoming an independent fern. Stolons serve as a primary method of vegetative propagation for many fern species, allowing them to rapidly multiply and spread across suitable habitats.
It is important to distinguish stolons from rhizomes, which are also horizontal stems but typically grow either underground or just at the soil surface. While rhizomes can also produce new shoots and roots, they primarily function as storage organs and a means of gradual expansion for the parent plant. Stolons, or runners, are specifically adapted for rapid outward spread and the formation of distinct, new, often detachable, plants along their length. This difference lies in their primary function and typical growth pattern relative to the soil surface.
Common Ferns with Runners
Many popular fern varieties are known for their runner-producing habits, making them excellent candidates for propagation. The Boston fern (Nephrolepis exaltata) and its cultivars, such as ‘Dallas Fern’, are prime examples of ferns that readily produce long, arching stolons. Their runners can extend several feet from the parent plant, with small plantlets forming at regular intervals along their length. Each plantlet typically develops a few small fronds and a nascent root system, making them easily identifiable.
The Lemon Button Fern (Nephrolepis cordifolia ‘Duffii’) also sends out thin, wire-like runners that can root to form new clusters of foliage. While not true stolons, some ferns like the Kangaroo Paw Fern (Microsorum diversifolium) have superficial, creeping rhizomes that behave similarly by spreading across the soil surface and producing new fronds and roots at nodes. These examples showcase the various ways ferns utilize horizontal growth to expand their presence.
Propagating Ferns from Runners
Propagating ferns using their runners is a straightforward and effective method. One common technique involves pinning a plantlet forming on the runner directly onto the surface of a pot filled with moist, well-draining potting mix. Gently pressing the plantlet’s base into the soil and securing it with a U-shaped pin or small rock encourages root establishment. Consistent moisture around the pinned section is important for successful root development.
Once the plantlet has developed a robust root system (typically after several weeks to a few months), it can be carefully severed from the parent plant, allowing the new fern to grow independently. Alternatively, if a plantlet on a runner has already developed sufficient roots and fronds, it can be gently detached and immediately potted into its own container. Ensure the new pot contains a suitable fern-specific potting mix that retains moisture without becoming waterlogged.
Another approach for plantlets not yet rooted is to place a detached plantlet with some runner attached into a small container of water. This allows roots to develop in a water-only environment before transplanting to soil. Providing warmth and consistent humidity will support the successful establishment of the new fern.
Caring for Ferns with Runners
Caring for ferns that produce runners involves managing their natural tendency to spread. If left unchecked, runners can quickly extend beyond the confines of a pot, creating a sprawling appearance. For container-grown ferns, selecting a pot with ample surface area allows runners to spread and root into the same container, creating a fuller plant, or they can trail over the pot edge for a cascading effect.
Regular observation helps determine if the fern is becoming too dense or if runners are spreading into undesirable areas. If propagation is not desired, runners can be trimmed close to the parent plant using clean, sharp scissors. This practice maintains a tidy appearance and directs the plant’s energy towards producing more fronds on the main plant. Providing adequate light and humidity, typical for most ferns, also supports their overall health and vigor.