Fern division is a straightforward and highly effective horticultural practice used to propagate new plants and rejuvenate older specimens. This method involves the asexual reproduction of the fern by physically separating its root structure into smaller sections. Gardeners commonly employ division to manage the size of mature ferns and increase the number of plants without relying on spore propagation. New plants are genetically identical to the parent.
Identifying the Right Time and Necessity
The most favorable time for dividing ferns is during relative dormancy, typically in early spring as new growth (fiddleheads) emerges, or in the early fall. Dividing then allows new sections to establish root systems before the active growing season or deep winter cold. Indoor ferns, which lack seasonal dormancy, should be divided when their root mass has completely filled the container, a condition called “pot-bound.”
A mature fern signals its need for division through several observable changes. Overcrowding, where fronds become too dense and lack vigor, is a primary indicator. Reduced frond size compared to previous seasons also suggests the plant is struggling. Sometimes, the center of a large, clumping fern may begin to die out, leaving a hollow area that requires separation and revitalization.
Preparation and Excavation
Before beginning, gather the necessary tools: a clean, sharp knife or serrated trowel, a shovel, and containers filled with fresh, well-draining potting mix. Thoroughly watering the fern two days prior is beneficial, as hydrated roots are more resilient and less prone to damage during handling.
For in-ground ferns, use a shovel to cut a circle approximately six inches away from the outermost fronds. Drive the shovel straight down to sever feeder roots, then carefully lever the entire root mass out. For a potted fern, gently invert the container and tap the rim to loosen the root ball, guiding the plant out by the base of the fronds. Once exposed, gently brush or shake away excess soil to better assess the structure of the roots and crowns before separation.
The Division Process
Fern division technique depends on its root structure, which falls into two main categories: clumping and running. Clumping ferns, such as the Boston fern, form dense root balls with multiple growing points, or crowns. To divide these, the root mass must be cut directly through the thick, fleshy crown using a sharp knife or serrated tool. Ensure each new section retains at least one viable crown and a substantial network of roots.
Running ferns, like some species of Christmas fern, spread via horizontal stems called rhizomes. These rhizomes may grow above or just below the soil surface, producing fronds at various points. Dividing running ferns is accomplished by cutting the rhizome into segments, with each segment needing at least one actively growing frond or a dormant bud (“eye”). Discard any old, dead, or mushy sections, especially from the center of clumping varieties, as they will not recover.
Post-Division Care and Replanting
The newly separated fern divisions must be replanted promptly to prevent the roots from drying out. When replanting, ensure the crown of the fern—the point where fronds emerge—is positioned at the same soil level as the original plant. For container planting, select a pot only slightly larger than the new root ball, using a rich, well-draining soil mix.
Immediate and thorough watering is necessary right after replanting to settle the soil and eliminate air pockets. The new divisions should be kept consistently moist during the establishment phase. To mitigate transplant shock, place the newly planted ferns in a sheltered location with diffused light, away from harsh sun and strong drafts. Maintaining high humidity for the first few weeks, perhaps by misting or placing them on a tray of pebbles filled with water, will aid their survival and growth.