Landscaping With Ferns
Ferns are some of the oldest members of the plant kingdom. Existing long before the dinosaurs roamed the earth, fossil evidence indicates they have been around at least 300 million years. Along with club mosses, spikemosses, horsetails, and quillworts, ferns belong to the Pteridophyte family, which accounts for some of the most diverse plants on earth. Ferns do not bloom, yet they are the most ornamental of plants. Their lush foliage, diverse textures, and complex forms make them an excellent choice for a wide variety of landscapes.
Once established, ferns are undemanding and require very little care. They grow in shady environments that would discourage fussier plants. Most fern species prefer slightly acid, woodsy soil, with regular moisture. The accompanying photo is of a fern garden that has existed since the 1930s and possibly longer. For the past 23 years, the current property owner has left the ferns alone to grow as they please. Despite their benign neglect, they are quite healthy and happy as well as extraordinarily beautiful in their woodland setting.
Ferns have no flowers, but the beauty, variety, and graceful presence they lend to the garden make up for any lack of floral display. The nature and botanical structure of ferns is actually much more complicated than can be expressed within the scope of this article. However, to understand the unique nature of ferns, it’s useful to consider a few basics regarding their botanical structure.
Roots. The roots of ferns are produced by underground structures called rhizomes. The rhizome may be one of two types, creeping or clumping. Creeping rhizomes grow from several inches to one foot per year and form a large colony. Clumping rhizomes are slow growing and form a tight clump. Knowing whether a fern is a creeper or a clumper is an important fact to take account when incorporating these plants into your landscape.
Stems. A fern stem arises from the growing tip of an underground rhizome. The portion of the stem just above ground and below the leafy structure is called a stipe (stalk). The stipe, which bears scales, hairs or glands, acts as a support structure and connects the root to the leafy part of the plant. The upper part of the stem or mid-rib (main axis), bearing the leafy structure, is called a rachis.
Fronds. The leafy structure of a fern is called a frond. Its complete “leaf” is made up of two parts, a stipe and a more or less triangular blade (leafy part). Reduced to very basic terms, a blade is either simple (undivided) or compound (divided into leaflets called pinnae). As a new frond emerges from the crown of the plant, it is tightly coiled into what is known as a crozier (similar in appearance to a shepherd’s crook) or fiddlehead (similar in appearance to the head of the musical instrument).
Reproductive structures. Ferns are fundamentally primitive plants that reproduce by microscopic one-celled reproductive units called spores. This distinguishes ferns from flowering or cone-bearing plants. The spores are produced in sac-like structures called sporangia. The sporangia are aggregated in groups called sori (or sorus, singular) on the underside of the frond. Sori contain both egg cells and sperm cells. The arrangement, location and number of sori are used to help identify fern species.
NATIVE FERNS COMMONLY GROWN IN THE MID-ATLANTIC AREA
Approximately 12,000 fern species are scattered worldwide. Ferns are native to every part of North America, from the hot, dry desert regions of the Southwest to the humid, moist swamps of the South to the cold mountainous areas of the North. The United States National Arboretum website states that more than 500 kinds of hardy ferns can be grown in American gardens. About 100 species inhabit the northeastern part of the country alone. The list below includes a sampling of ferns that are native to the Mid-Atlantic area. The actual list of native ferns is far too extensive to include in this article.
Ebony Spleenwort (Asplenium platyneuron) is an erect, strongly vertical fern species averaging 8” to 22.” Native throughout the entire eastern half of the United States, this evergreen clumping species prefers light shade and basic or slightly acidic soils. It has alternate pinnae that overlap the rachis. Reputed to cure disorders of the spleen and liver, it was named by Pliny the Elder and comes from the Greek (a = without and splen = spleen).
Christmas Fern (Polystichum acrostichoides) is an easily recognized evergreen species commonly found in shaded woodland settings in the wild. It produces 1’ to 2’ long glossy, deep green fronds and has a slightly coarser texture than most ferns. It provides a bit of much needed color in the winter landscape although it may mat down from the weight of snow on the fronds. In spring, pewter-colored fiddleheads emerge from the crown and the old fronds fade away as the new ones mature. Christmas fern is one of the most shade- and drought-tolerant ferns for this area of the country. While it prefers a shady setting, it will take some sun if the soil is moist.
Cinnamon Fern (Osmunda cinnamomea), one of the tallest of the native ferns, grows in full sun or light shade in ordinary garden soil and will grow even taller in consistently moist, even wet, soil. Give it plenty of space in the landscape because it can get to be quite large. This clump-forming beauty gets its name from the cinnamon-color shaggy sporangial (spore-bearing) cases on the ornamental fertile fronds. Hummingbirds sometimes use the shaggy “wool” for nesting material. The 3’ to 5’ long pale green fronds turn a darker green color during the summer. In autumn, the green fronds fade to a bronze-yellow hue.
Hay-scented Fern (Dennstaedtia punctilobula) gets its name from the sweet, hay-like scent it gives off when the foliage is bruised. It spreads by shallow rhizomes that sprout new 3’ long fronds approximately every 3 inches. This fast-growing creeper can rapidly form colonies and can become invasive in certain settings. In fact, it is considered a nuisance plant in some northern states where impenetrable stands of it cast dense shade on the forest floor reducing plant and wildlife diversity. It is generally not a good choice for the mixed shade garden where it might crowd out other species. However, if planted in the right setting, it can be a very effective ground cover for sun or shade and a useful way to suppress weeds. In fall, the foliage turns pale yellow or copper.
Interrupted Fern (Osmunda claytoniana) grows in an upright spreading-vase form and looks similar to cinnamon fern but is lighter green in color and has broader pinnae. Interrupted fern normally grows about 2’ to 4’ tall, but it can stretch up to 5’ tall in fertile, consistently moist soil. This fern gets its name from the location of the spore-bearing pinnae that develop in the middle of the frond, thus “interrupting” the pinnae formations. The pinnae fall off in mid-summer, leaving the stem bare in the middle. Osmunda fern species grow from heavy rhizomes and are the source for Osmunda fiber, the material used to pot orchids. Like many ferns, this species may take several years to become established.
Lady Fern (Athyrium filix-femina) has delicate, lacy 3’ long fronds that unfurl pale green and turn darker green as the season progresses. Lady fern often mutates, creating various semi-crested or ruffled variations. It has also been crossed with some of the Asian Athyrium species to create interesting new hybrids. This North American deciduous species is one of the easiest of the native species to grow. It grows from slowly creeping rhizomes and is capable of adjusting to sites with varying degrees of sun or shade provided the soil is reasonably moist. This fern, widely distributed throughout North America, is also common in Europe. In fact, about 200 species of Athyrium are distributed worldwide.
Maidenhair Fern (Adiantum pedatum) is one of the most elegant and graceful of our native species. A clumping species, it typically spreads slowly by creeping rhizomes in well-drained organic soil. Its bright green, 12” to 20” long, bright green, fingered fronds cascade in layers on shiny, black stems. While maidenhair fern thrives in bright light, it cannot tolerate direct sun. Once the fronds wilt from heat or drought, they cannot recover and the plant must produce new fronds. Don’t confuse this species with Adiantum tenerum or A. capillus-veneris, both of which are grown as houseplants.
Marginal Wood Fern (Dryopteris marginalis) is an attractive, sturdy, evergreen clumper that forms from a single crown. The 1’ to 2’ long fronds are dark green, leathery, and somewhat formal in appearance with their erect to arching growth habit. Although quite graceful, this species is a bit of a prima donna regarding moisture. It likes humus-rich, acidic, well-drained soil but it doesn’t like for the soil to dry out. As a result, it may require a little more attention than most ferns to hit that sweet spot.
Ostrich Fern (Matteuccia struthiopteris) is one of the tallest and most impressive looking of the native fern species. Topping out at 4’ to 6′ tall, it has bright green, upright deciduous fronds that circle a narrow base. The brown, spore-bearing fronds, which are separate from the green fronds, harden and persist through cold weather, lending an architectural element to the winter landscape. This is the fiddlehead fern that restaurants and home cooks prize for its grassy, asparagus-like flavor. A deciduous species, ostrich fern thrives in average to moist soil and dappled sunlight. This creeper spreads by shallow, string-like rhizomes, which produce new clumps a foot or two away. It can easily naturalize in sites with dappled sunlight. In northern parts of the country, it will grow in full sun as long as it has moist soil.
Royal Fern (Osmunda spectabilis) is a tall, stiffly erect, regal-looking fern species commonly found in moist woods throughout much of the Mid-Atlantic region. It adapts well in moist-to-wet areas allowing it to tolerate bright shade to full sun. With constant moisture, this clump-forming species can reach 6’ or more. Like the other Osmunda species, royal fern has good fall color, turning a soft golden shade. The fiddleheads are quite elegant but are believed to be carcinogenic and should not be eaten.
NON-NATIVE FERN SPECIES
As some of the oldest plant species on the planet, many of the ferns we consider native also grow in other parts of the world, the same species overlapping between eastern North America, western Europe, and eastern Asia. A few non-natives and hybrids that have grown in popularity in this country are listed below.
Autumn Fern (Dryopteris erythrosora) is common in the temperate forests of Asia. It emerges in the spring bearing shiny, red foliage, which fades to 2’ to 3’ long glossy green fronds in summer. The green is punctuated throughout the growing season with the appearance of new red fronds. Once established, this fern is very drought tolerant. ‘Brilliance’, one of the better known autumn fern selections, produces brighter red growth than the species and lasts longer into summer.
Japanese Painted Fern (Athyrium niponicum ‘pictum’) received the Perennial Plant of the Year Award in 2004 from the North American Perennial Plant Association. The first fern to be so honored, this popular outstanding Asian selection is highly versatile due to its blend of silvery green and burgundy colors on 12” to 18″ fronds. One of the most colorful of ferns, it shows up well in partial shade and blends well with other fern species.
Japanese Holly Fern (Cyrtomium falcatum) gets its name from the resemblance of the pinnae to holly leaves. Introduced in various southern states, including Virginia, this Asian species has naturalized in many areas of the world. Often used as a houseplant, its lustrous, bold, arching, leathery foliage is very dramatic, planted either as a single specimen or in large swaths. Although somewhat evergreen, it often looks quite tattered in the winter months.
Ghost Fern (a hybrid of Athyrium niponicum var. ‘pictum’ and Athyrium filix-femina) is a slow-growing clump-forming deciduous hybrid that typically grows about 30” tall. It has a bushy, vertical habit composed of fronds that are a soft grayish-green color. This hybrid combines the elegant, upright growth of our North American native lady fern with the ghostly silvery gray coloring of Japanese painted fern. Contrasting dark maroon midribs heighten the effect. The silver color is best in the spring, its fronds becoming more grayish-green with the onset of hot weather.
Crested Lady Fern (Athyrium filix-femina ‘Dre’s Dagger’) is a unique, dwarf form of our native lady fern. It has dark green fronds that are symmetrically split into a three-dimensional, criss-cross pattern. Use it as a feature at the front of an evenly moist, shady border where you can appreciate such a distinctive and intricate leaf structure.
CULTURAL REQUIREMENTS OF FERNS
Soil – In general, ferns prefer moist but well-drained soil that has been amended with a generous amount of organic material. Most ferns can tolerate poor soil and a pH of 4 to 7.
Light Requirements – Although partial to shade, some species, such as lady fern (Athyrium felix-femina) and hay-scented fern (Dennstaedtia punctilobula) can tolerate some sun provided the soil is somewhat moist.
Water Requirements – In general, ferns prefer consistently moist soil, but some species can tolerate wet soil while others can tolerate drier conditions.
Pests and Diseases – Slugs may attack ferns in late spring but, in general, these plants are free of pests and diseases. Deer, rabbits, and other mammals don’t normally bother them.
Spring care – Divide and transplant ferns as soon as new growth appears. Ferns may need to be divided if the fronds appear to be smaller than in previous seasons or if a dead area develops in the center of the clump. To divide the clump, dig up the entire plant and cut the most vigorous parts into sections. Replant the divisions at the original depth. Keep the divisions moist until they are well established.
Summer care – Provide supplemental water if there’s not enough rain to keep the soil moist.
Fall care – After a killing frost, cut the dead foliage of deciduous species back to the crown.
LANDSCAPING WITH FERNS
Ferns are quite useful all year round in the landscape. The exotic-looking, bright green “fiddleheads” of many fern species add instant texture and interest to the spring landscape. The lush, dark-green foliage provides a cool, calming presence in the summer garden. In fall, some fern species turn golden yellow or coppery brown, blending in with all the various autumn hues of woody and herbaceous plantings. In winter, a few hardy fern species provide color and texture to an otherwise dull landscape.
There’s a fern for every need. Upright ferns such as royal fern, cinnamon fern or ostrich fern offer height and drama. Lady fern, ebony spleenwort, and some of the wood ferns (Dryopteris species) provide a round or mounded shape. Maidenhair fern, Japanese painted fern, or autumn fern lend a pleasing cascading or draping effect.
Armitage’s Native Plants for North American Gardens (Armitage, Allan M. 2006)
Native Plants of the Southeast, A Comprehensive Guide to the Best 460 Species for the Garden (Mellichamp, Larry, 2014)
The Plant Lover’s Guide to Ferns (Steffen, Richie and Olsen, Sue, 2015)
“Ferns of the Blue Ridge,” U. S. Department of Agriculture Forest Service General Technical Report SE-15 (Krochmal, Arnold and Connie, 1979)
“Rain Garden Plants,” Virginia Cooperative Extension Publication 426-043, Va.Coop.Ext.vt.edu
Piedmont Virginia Native Plant Database, Ferns Native to Albemarle County
The United States National Arboretum, FAQs on Ferns