Japanese Ferns for Temperate Gardens

By: Sue Olsen

Susan Olsen is the proprietor of Foliage Gardens, a mail order fern nursery specializing in temperate ferns, and author of…

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Nature made ferns for pure leaves to show what she could do in that line.

Henry D. Thoreau

For many gardeners the love of plants dates far back into childhood where, with no formal instruction, the child was touched by some magic of nature — perhaps the first snow­ drops or crocuses of spring, a fragrant rose, the beguiling face of a pansy, or even the delightfully perverse pleasure of puffing the seeds of a dandelion. Only a few, however, have taken up gardening because of tranquil woodland memories of a particular fern. It is usually not until much later in life (and sometimes never ) that the subtleties of form and texture equal the attraction of a flower. Ferns, of course, have no flowers, but their varied greenery can give unity to the most colorful gardens, and their diversity can provide a lifetime of study and fascination.

Many growers start their fern collections with natives — an excellent idea — or some of the many cultivars from Great Britain, but some of the best species, especially evergreens, are from Japan. There are choices for every garden size and situation, and many are colorful as well. Among the most readily available are several landscape workhorses, some of which were initially introduced to U.S. growers as indoor plants — Dryopteris erythrosora, Polystichum tsus-simense, P. polyblepharum, and the cyrtomiums — and then delighted the adventurous by proving hardy outdoors.

Polystichums

Polystichum tsus-simense, with dark, conifer-green fronds twelve to fifteen inches tall, is one of the most familiar of Japanese ferns. Readily identifiable by its prominent black mid-rib, it combines well with primulas in the shady woodland or, as a plucked frond, with the rose in one’s boutonniere, as it has long been used in flower arrangements. Evergreen as are most polystichums, P. tsus-simense is easily established and tolerant of a wide range of temperatures. The closely related P. rigens is somewhat taller and more emerald green, but otherwise similar in appearance. It is rare and thus appeals to the collector’s appetite, but don’t be disappointed if friends can’t distinguish it from your P. tsus-simense.

Polystichum polyblepharum, tassel fern, is incomparable for landscaping, appreciated by novices for its ease of cultivation and admired by all for its polished evergreen growth. Large, shaggy, silvery scales clothe the emerging fiddleheads like frosting, and as growth progresses the immature fronds flip over backwards, giving the effect of a tassel. Vase-shaped and eighteen inches to two feet tall, this fern serves well as a shady-foundation plant. Its shiny fronds combine well with azaleas and camellias. Two recent introductions, P. neolobatum and P. makinoi (the latter a microscopic joy with three varieties of scales) are equally valuable for their hard-lacquered, spiny, evergreen foliage. They are attractive as individuals and provide complementary unity when planted with P. polyblepharum or, for contrast, with grassy-leaved accents.

Dryopteris erythrosora. Photographs by the author.

Dryopteris erythrosora. Photographs by the author.

Dryopteris

Dryopteris erythrosora, autumn fern, is a widely distributed evergreen whose common name refers to its rosy new growth, which is displayed in spring rather than autumn. It has broadly ovate blades (the leafy portion of the frond) and usually reaches thirty inches in cultivation. With the same shade and soil requirements, it is handsome when planted with rhododendrons, particularly those of the lepidote series with coppery pink new growth, and, for the same reason, with epimediums as ground covers. Dryopteris erythrosora var. prolifica, equally russet in vernal leafage, is less common, lower growing, and far more finely and openly cut. It has buds along the rachis (stem) that can be pricked off and nurtured in a covered pot of moist peat to produce progeny without the labor, time, and hazards of spore culture.

Dryopteris crassirhizoma

Dryopteris crassirhizoma

Colorful new growth on ferns is not limited to pigmentation of the fronds. The emerging croziers of Dryopteris wallichiana, for example, are fresh apple-green offset by a cloak of black scales. The scales persist in counterpoint as the fronds mature to a leathery, dark green. This fern grows to three feet tall or more and is an attractive understory with those of the Japanese maples that have light green new leaves. D. crassirhizoma is a more cold-tolerant cousin of D. wallichiana. Smaller in stature, it presents a similar display when unfurling, but is slow to establish and resists transplanting. However, it is well worth patience and pampering as, once established, it is an ornamental prize. D. cycadina, often listed as D. atrata, and the coveted rarity D. polylepis also dress for spring in scaly black, the latter so copiously covered with scales that one wonders whether Mother Nature forgot the chlorophyll.

In contrast with the above evergreens, the visually distinct Dryopteris sieboldii looks like a Polypodium aureum with confused sporangia. It has pale blue-green, wavy fronds that extend like scabbards. Over thirty inches tall and frighteningly late with its new growth, it makes a bold blue backdrop for delicate tracery garden designs.

No collection of Japanese dryopteris would be complete without a specimen of Dryopteris championii. Rather ordinary in appearance as a juvenile, it eventually develops lustrous thirty-inch evergreen fronds similar in shape and division to those of D. erythrosora. It is reliably hardy and should be used wherever the landscape tapestry needs radiance.

Cyrtomiums

Cyrtomium falcatum, holly fern, is valued for its unusual outline, which gives it a holly-like appearance. Variable and quite hardy, its satiny, sickle-shaped pinnae (leaflets) give life to the low-light garden, where it serves as an excellent foil for more finely textured plants. Many cultivars with fronds displaying varying amounts of cresting, forking, and other distortions have evolved, but the species itself is the most resistant to cold. C. caryotideum and C. macrophyllum, with large, tulip-shaped pinnae, are even bolder landscape specimens. Over one foot tall and evergreen in the Pacific Northwest, they are particularly attractive when the netted venation of the pale yellowish green fronds is backlit in the garden.

Other Japanese Ferns

The arachniodes include a number of tempting choices, though they are not all commonly available. Arachniodes aristata, East Indian holly fern, has attractive glossy leaves; A. aristata ‘Variegata’ has a light creamy stripe down the mid-rib; and A. standishii, the aristocrat of the genus, has finely dissected fronds that form a long, tapered filigree. Regrettably, this hardy evergreen ornamental, a fine companion for broadleaved evergreens, reproduces only reluctantly from spores. Once germinated, however, it is not difficult to grow. A. aristata can be grown in mild climates (if necessary, indoors) wherever shiny foliage is effective. The variegated cultivar, with its leathery fronds, is particularly valuable in somewhat sunny situ­ations where other ferns would wither.

American gardeners have struggled, often with fatal results, to domesticate the Hartford fern (Lygodium palmatum), which not only disappears in cultivation, but is becoming increasingly rare in nature and should never be collected. The same ornamental effect is more easily achieved with the Japanese climbing fern (L. japonicum). Given support, this vine-like fern can readily achieve a height of eight feet or more and, given a mulch (oak leaves are excellent), can survive such disagreeable winter temperatures as are found on the eastern shores of the United States. The sterile lower foliage is delicate, with even more dissected fertile pinnae at the outermost extremities. Do cut plants back to the ground before new growth emerges in spring or be prepared to face a hopeless tangle of new and old fronds.

Although not evergreen, Athyrium niponicum ‘Pictum’ is prized even among gardeners with only a token interest in ferns. Occasionally listed as A. goeringianum or A. iseanum ‘Pictum’, it is universally recognized by its common name, Japanese painted fern, which refers to the variable blend of green, blue, gray, and burgundy hues on the fronds. Averaging eighteen inches tall, the fronds generally are parallel to the ground at maturity, so the plants make an attractive accent when grouped as a ground cover, especially in the company of dark blue-green leaves. The species itself, A. nipponicum, has fronds of restful, soft green with hints of color that, while less dramatic than those of the cultivar ‘Pictum’, are easier to blend into the landscape.

Athyrium otophorum

Athyrium otophorum

A new introduction, Athyrium otophorum, another painted fern, combines a subtle blend of pale, lime-green pinnae with raspberry “paint” on the stipe (petiole) and rachis suffused slightly onto the fronds, giving the impression of swirled sherbet. Two feet tall and rather erect, it is close to being evergreen in mild winters and gives a lift to somber, dark areas of the garden.

Osmunda lancea

Osmunda lancea

For paleontologists, geobotanists, and the curious who enjoy the marvels of life on earth, it is interesting to note that a substantial number of plants native to the eastern United States are believed to have migrated there via a prehistoric land bridge from Japan. Among the ferns are the primitive osmundas, whose fossil remains can be found on all seven continents. Osmundas are tall, individualistic plants for the background in the garden bed, where several offer welcome variation. Osmunda japonica and O. lancea, both with red young fronds, resemble the royal fern (O. regalis), but are smaller in all of their parts and are the closest the osmundas come to being feathery. With leaves suggestive of locust trees, they provide valuable contrast with traditional fern foliage in a moist glen. These ferns are deciduous and should be planted where a void is tolerable in the winter landscape. As the spores of this genus are green when ripe, they are viable only for a short time and should be sown immediately after harvesting.

There are several highly desirable Japanese choices among the popular maidenhairs that are much sought out by the horticultural community. Adiantum pedatum from Japan is similar in form to the North American A. pedatum, but the spring fronds fan out in bronzy hues. A. capillus-junonis is a small, slender rarity with elongate, once-pinnate fronds that are coppery pink. This fern occasionally tip roots and can be propagated in this manner. A. monochlamys is a light and airy, small evergreen with triangular fronds, rather like a non-spreading version of A. venustum. It is, however, slow to come from spores, a feature often reflected in its price, and it deserves deferential placement in the landscape. It is handsome when silhouetted against a blackened log or non-salty driftwood and surrounded by lilliputian shade-lovers. The soil should be enriched with a small amount of lime (egg shells will do).

Finally, there are the aspleniums — small treasures for the foreground of the garden. Usually once-pinnate, the fronds are willowy and lacy in appearance with pinnae like little beads strung along the stem. Asplenium sarelii, A. varians, and the circumboreal A. trichomanes are all tidy evergreens rarely more than eight inches tall. These ferns appreciate good drainage and make excellent subjects for the shady rock garden, the collector’s trough, or even a niche in the garden wall.