Know Your Natives – The Majestic Royal Fern

The Royal Fern, belonging to the Osmundaceae family, is an extraordinary herbaceous plant native to the United States. With its crown of clustered spore cases on the fertile fronds, this fern stands out as a regal and admirable beauty. Its habitat preference includes mostly sunny areas with consistently wet to occasionally flooded soils, making it a fascinating addition to wetlands, marshes, and bogs.

A Fern Fit for Royalty

The name “Royal Fern” originates from the Latin word “regalis,” meaning “regal” or “royal.” It perfectly describes the fern’s majestic appearance and grand size. The specific epithet, “spectabilis,” adds to its allure, translating to “admirable” and “spectacular.” This fern, also known as the American Royal Fern, can be found throughout Arkansas, thriving in its native environment.

A Closer Look

The Royal Fern boasts a stout and elongated rootstock, which can be oriented vertically or horizontally, depending on the habitat. The rootstock is covered by dense, black, wiry, and tough fibrous roots, forming a protective shield. The emergence of new fronds occurs at the apex of the rootstock, surrounded by remnants of previous year’s leaves. In the case of vertically positioned rootstocks, the apex may elevate above ground level, while horizontally oriented ones remain at duff level.

During early spring, the Royal Fern unveils large fiddleheads that gradually unfurl into smaller fiddleheads before transforming into leaflets called pinnae. The initial fiddleheads are covered with matted pubescence, which eventually drops off as the leaf stalk and midrib elongate. The fronds are bipinnate and have pinnae elongating up to 12 inches. The fern’s appearance varies depending on the habitat and season, with fronds ranging from erect to ascending or arching. As the fall approaches, the fronds decline, and aside from the frond stubs, they disappear entirely during winter.

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Photo 2: In early April, newly emergent fiddleheads are temporarily covered with matted pubescence.

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Photo 3: Fiddleheads remain mostly closed as stipes elongate to several feet tall. Fern at lower right is lady fern (Athyrium filix-femina).

The Splendor of Fertile Fronds

The fronds of the Royal Fern typically measure 2 to 4 feet in length, occasionally reaching a maximum of 6 feet, and are about half as wide. The widely spaced pinnae grow up to 12 inches long. Both sterile and fertile fronds have a similar vegetative structure, but the upper pinnae and pinnules of fertile fronds lack chlorophyll and are modified into clusters of spore-producing sporangia. These sporangia, initially dark green, mature from the frond’s apex downward. As they mature, they turn lighter green to golden brown, splitting across the top to release the spores. The sporangia then wither, while the lower portion of the fertile fronds remains green and photosynthetic.

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Photo 4: Sporangia of plants on left are green while those of plants on the right have become brown after the release of spores. Lady fern (Athyrium filix-femina) at the lower right and Christmas fern (Polystichum acrostichoides) at the lower left.

Pinnae on both sterile and fertile fronds bear six to twelve pinnules, measuring up to 2 inches in length and 3/8 inch in width. The pinnules are oblong in shape, with rounded apexes and rounded to truncate-oblique bases. The margins are slightly undulating and minutely serrate. Fertile pinnae are notably smaller in size. These fronds host spherical sporangia, occurring in small, naked, short-stalked clusters. As the sporangia mature, they change color, turning from dark green to golden brown, until they split open to release the spores. The upper portion of the fertile fronds quickly shrivels, while the lower portion remains green and continues to photosynthesize.

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Photo 5: An 18-inch long section of a 4-foot long fertile frond. Fertile (sporangium-bearing) pinnae are significantly smaller than sterile, photosynthetic pinnae.

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Photo 6: Clusters of sporangia replace leafy pinnules at tips of fertile fronds. Sporangia split across their tops for spore dispersal.

A Fascinating Life Cycle

After the spores are dispersed, the reproductive phase of the fern’s life cycle comes to an end. The spores germinate in the soil, giving rise to a prothallus, also known as the gametophyte phase. This tiny and ephemeral prothallus produces gametes, including sperm and eggs. The mobile sperm swim through the ground’s moisture to fertilize the eggs, which remain attached to their prothallus. Fertilization leads to the development of a zygote, eventually growing into a large and perennial sporophyte plant. This complex life cycle is often described as an “alternation of generations.”

Fit for a Garden

The Royal Fern thrives in mesic (shaded) to hydric (sunny) areas of native plant or fern gardens. Although it dies down to the ground during winter, this herbaceous fern showcases its beauty throughout spring, summer, and fall. Its large, bold structure, combined with its elegant and graceful fronds, makes it a striking addition to any garden, whether as a single plant or a magnificent colony.

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Photo 7: In fall, fronds recline and become more yellowish. Photo-October 23.

Ferns of the Same Family

Apart from the Royal Fern, two other ferns belonging to the Osmundaceae family can be found in Arkansas: the Interrupted Fern (Osmunda claytoniana) and the Cinnamon Fern (Osmundastrum cinnamomeum). While the Royal Fern has fully divided pinnae, the other two ferns have lobed pinnae that are not completely divided. The sporangia of the Interrupted Fern are located on fertile pinnae below the apex of fertile fronds, while the Cinnamon Fern has separate fertile fronds that bear sporangia exclusively.

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Rediscovering the Royal Fern

Recent genetic studies suggest that the Royal Fern found in North America may be a separate species known as Osmunda spectabilis. However, this reclassification has not been widely accepted within the botanical community. Regardless, the Royal Fern remains a botanical treasure with its majestic appearance and fascinating life cycle.

Article and photographs by ANPS member Sid Vogelpohl

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Discover More About the Royal Fern

To dive deeper into the captivating world of the Royal Fern, visit the Ames Farm Center. Explore the vast array of native plants and gain valuable insights into creating your own flourishing garden.