Does the Rhizome of a Fern Grow Horizontally or Vertically?

Habit

• Ferns have two distinct growth habits -- spreading and clumping. Both types have rhizomes, which increase the size of plants by forming lateral extensions that produce new shoots above their lengths and roots below. The spreading rhizomes of bracken fern (Pteridium aquilinum), hardy in U.S. Department of Agriculture (USDA) plant hardiness zones 3 through 10, may extend 20 feet underground. Royal fern (Osmunda regalis), which is hardy in USDA zones 3 through 9, forms tidy clumps that rarely spread more than 3 feet.

Reproduction

• Although ferns reproduce sexually by spores, they also reproduce asexually by their rhizomes. Spores are often unreliable in their ability to germinate because they are at the mercy of environmental variables. The dustlike spores must land in a place that keeps them moist until they germinate, which is often a difficult challenge. Rhizomes provide a more reliable way of reproducing because they stay attached to the parent plant -- similar to an umbilical cord -- while the nutrient transport system within the fern nourishes the developing roots and shoots through the rhizomes.

Division

• You can divide your fern by cutting through its rhizomes, ensuring to separate it into clumps that contain roots. Even delicate-looking ferns can tolerate a little rough handling when they are divided, according to a University of Georgia College of Agricultural and Environmental Sciences website article. If your fern has outgrown its container or spread beyond the confines of a garden area, you can slice through the clumps with a sharp knife or shovel, and separate them into wedges or small, individual sections. Replant the sections, which are new plants, in moist soil by spreading the roots at the base of the plants, and mist the ferns daily until the roots anchor themselves in their new locations.

Exceptions

• A curious exception to rhizomes that grow horizontally is found in a group of epiphytic ferns commonly called “foot ferns.” Rhizomes of foot ferns are typically fuzzy and creep up and over containers, rocks and logs like little feet that often resemble their common names. While horizontal rhizomes are typical of terrestrial ferns, vertically growing rhizomes are characteristic of epiphytic ferns, which grow in nature on plant hosts. The vertical rhizomatous growth is an adaptation that allows foot ferns to anchor themselves to trees and absorb moisture and nutrients from the atmosphere. Rabbit’s foot fern (Davallia fejeensis) is hardy in USDA zones 10 through 12 and commonly grown as a houseplant outside that range. Its furry rhizomes have a silvery-gray cast, reminiscent of true rabbit feet. Squirrel’s foot fern (Davallia mariesii) has reddish-brown rhizomes and grows as a perennial in USDA zones 9a through 11.