Licorice Fern

Polypodium glycyrrhiza is native to western North America, with a range extending from southern Alaska through British Columbia, Washington, Oregon, and into northern California.

• Its distribution closely follows the moist coastal and montane forests of the Pacific Northwest
• It is particularly abundant in the temperate rainforests of the Olympic Peninsula and the coastal ranges of Oregon and Washington
• The species is considered an indicator of old-growth and mature forest ecosystems in some regions
• Fossil records of the genus Polypodium extend back to the Eocene, though direct fossil evidence of P. glycyrrhiza is limited

The Licorice Fern is a small to medium-sized perennial fern, typically growing 15 to 40 cm tall.

Rhizome & Stipes:
• Rhizome is long-creeping, branching, 3–6 mm in diameter, densely covered with golden-brown to reddish-brown lanceolate scales
• Rhizomes have a distinctly sweet licorice-like taste when chewed
• Stipes (leaf stalks) are slender, straw-colored to pale green, 5–20 cm long, and smooth

Fronds:
• Fronds are once-pinnate (simply pinnatifid), narrowly triangular to lanceolate in outline, 10–35 cm long and 3–10 cm wide
• Pinnae (leaflets) are typically 5–15 pairs, alternate, linear to oblong, with entire to slightly wavy margins
• Texture is somewhat leathery (coriaceous); color is bright to dark green on the upper surface
• Fronds emerge singly along the creeping rhizome rather than in a clustered rosette

Sori:
• Sori are round, arranged in two rows on either side of the midrib on the underside of fertile pinnae
• Sori lack indusia (protective coverings), which is characteristic of the genus Polypodium
• Sporangia are mixed with slender, hair-like paraphyses
• Spores are yellow-brown when mature

The Licorice Fern occupies a unique ecological niche among North American ferns, frequently growing as an epiphyte or on moss-covered rocks.

• Commonly found growing on the mossy trunks and branches of Bigleaf Maple (Acer macrophyllum), where it accesses moisture and nutrients from accumulated organic debris
• Also grows on mossy rocks, rotting logs, and humus-rich soil in shaded forests
• Prefers moist, shaded environments with high atmospheric humidity
• Typically found at low to moderate elevations, from sea level to approximately 1,000 meters
• Strongly associated with coastal fog zones and areas with consistent moisture availability

Reproduction:
• Spores are dispersed by wind and require moist substrates to germinate
• Like all ferns, it has a two-stage life cycle: the familiar sporophyte stage and a small, independent gametophyte (prothallus) stage
• Sperm require a film of water to swim to archegonia for fertilization
• The creeping rhizome also allows vegetative spread, enabling the plant to colonize large areas of bark or rock surface over time

The Licorice Fern is occasionally cultivated as an ornamental fern for shade gardens and naturalistic plantings, particularly in regions with mild, moist climates.

Light:
• Prefers deep to partial shade; avoid direct sunlight
• Ideal for north-facing walls, shaded rockeries, and woodland gardens

Soil:
• Requires well-draining, humus-rich substrate
• Can be grown on mossy logs, in rock crevices, or mounted on bark slabs to mimic its natural epiphytic habit
• A mix of leaf mold, coarse bark, and perlite works well for container cultivation

Watering:
• Keep consistently moist but not waterlogged
• Benefits from regular misting to maintain humidity, especially in drier climates

Temperature:
• Hardy in USDA zones 6–9
• Tolerates light frost but performs best in mild, maritime climates
• Fronds may die back in winter in colder areas and re-emerge in spring

Propagation:
• Division of creeping rhizomes is the most reliable method
• Spore propagation is possible but slow, requiring sterile conditions and patience

Common Problems:
• Frond browning or dieback — usually caused by insufficient humidity or prolonged dry conditions
• Susceptible to scale insects when grown indoors
• Does not tolerate drought or hot, dry winds