Interrupted Fern Info: How To Care For Interrupted Fern Plants


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Growing interrupted fern plants, Osmunda claytoniana, is easy. Native to the Midwest and Northeast, these shade-tolerant plants grow in woodland sites. Gardeners add them to plantings of Solomon’s seal and hostas, or use the ferns to create a shaded border. Interrupted ferns even do well as erosion control plants on shaded slopes.

What is an Interrupted Fern?

Interrupted fern plants grow a vase-shaped rosette of erect to nearly erect 2- to 4-foot (.60 to 1.2 m.) high leaves. The common name for these ferns is derived from the broad fronds being “interrupted” in the middle by three to seven spore-bearing leaflets, called pinnae.

These middle leaflets, which are also the longest ones on the frond, wither and fall off in mid-summer leaving a blank space or gap on the stem. The leaflets above and below this interruption are sterile – they do not bear sporangia.

Interrupted Fern Care

This eastern North America native plant grows well in USDA zones 3-8. In the wild, it grows in shaded sites that are moderately wet. Growing interrupted ferns prefer sites with filtered sunlight, moist conditions, and sandy loam soils that are slightly acidic.

Interrupted fern care is minimal as long as the soil has adequate organic content, there is sufficient humidity, and the site offers protection from prevailing winds to prevent drying out. The plants may grow in more direct sunlight if their roots are in moist soil.

In spring, the plant’s dense mass of roots or rhizomes may be divided. These rhizomes are commercially harvested to create orchid peat used as a rooting medium for epiphytic orchids.

Interrupted Fern vs. Cinnamon Fern

Distinguishing interrupted fern from cinnamon fern (Osmunda cinnamomea) is difficult when just infertile leaves are present. Here is some interrupted fern info to help tell these plants apart:

  • Cinnamon fern petioles are more woolly-brown.
  • Cinnamon fern leaflets have pointed tips versus rounded tips of interrupted ferns.
  • Cinnamon fern leaflets also bear tufts of persistent, woolly hairs at the base of their stems.
  • Cinnamon ferns bear sporangia over the entire leaflet, whereas interrupted ferns plants only in the middle of their fertile leaves.

For more interrupted fern info, contact a local nursery or extension office in your area.

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Ferns for Sunny Locations

Most gardeners know that ferns are a great addition to the shade garden. However you may be surprised to learn that many are also suitable for sunny locations! The key to success is adequate moisture. This article will introduce you to the most sun-tolerant ferns.

Ferns are enjoying a surge in popularity these days. Using ferns as garden ornamentals is not a new concept. The UK fern craze of the Victorian times (coined ‘pteridomania') seemed to be the starting point with the discovery of hundreds of unique forms of native ferns. By the turn of the century, the craze subsided and ferns, while not falling completely out of fashion, did appear to lose their spark. Ferns became a plant of the specialist gardener. In the 1980s and '90s, ferns once more started to gain popularity. The discovery of new species in China, especially those with more colourful fronds with touches of grey, red and wine, suddenly upped the ante. The present day increase in fern popularity follows on the footsteps of the current Hosta craze. Hosta are perhaps the premier foliage plants grown by gardeners and with their tolerance to sun or shade (depending on the selection), they can be used in a myriad of garden situations. However, gardeners now needed some plants to contrast with their ever-growing Hosta collections. Ferns were the obvious choice. Today, ferns once more are becoming a mainstay in the garden scene.

Most gardeners associate ferns with shade. Certainly, the vast majority do grow in the shade of forests and rocky outcrops. For gardens with shade issues, ferns come highly recommended. But not all gardeners have to deal with shade and yet, they would like to incorporate ferns into the landscape design. Are there any ferns that can tolerate significant sun? The answer is yes! However, some soil amendments are required to have success.

The key to growing ferns in sun is maintaining adequate soil moisture. Many ferns grow in shade simply because the soil stays moister there than in full sun. If your have a growing area where the soil stays moist, then ferns in sun is a distinct possibility. Highly organic soil will help ensure better soil moisture. Maybe you have a naturally occurring moist pocket or a stream running through your property. Perhaps you have a sprinkler system that helps maintain evenly moist soil. Some gardeners even have man-made bog gardens. Any of these situation can allow for ferns to be grown under full sun situations, especially in more northern gardens. In southern gardens, the midday sun is probably still too intense, but as long as the ferns are shaded midday, they can tolerate morning and late afternoon sun. While many ferns can handle considerable sun if the soil remains evenly moist, some are better than others. Here are some of the most sun-tolerant species.

The genus Osmunda only contains three species the cinnamon fern, O. cinnamomea, interrupted fern, O. claytoniana and the royal fern, O. regalis. All of these ferns prefer moist to wet sites. Royal ferns are known to actually grow into the flowing water of streams. Due to their high moisture requirement, these species will not tolerate any drought however they will tolerate full sun. In fact, in my local area, cinnamon ferns typically grow in full sun. They are also very wind tolerant and will grow quite close to the ocean. Royal ferns also tolerate full afternoon sun and have the advantage of bronze-coloured spring growth. Interrupted fern seem to appreciate shade from midday sun but will certainly tolerate full morning sun. All of these species are deciduous and turn lovely shaded of yellow, copper to bronze in the fall. These are not small ferns most reach at least 3 feet, but they are not runners, rather they form large vase-like clumps. They are hardy to at least zone 3.

Details of the cinnamon fern

Above left is the royal fern while to the right is the interrupted fern

Among the genus Athyrium, the best species for sun is the lady fern, A. filix-femina. There are many named cultivars of this fern, many which date back to the fern craze of the Victorian era (this was the most popular fern at the time). In warmer climates, a little protection from the hottest midday sun will go a long way to prevent browning of the frond edges. Again, locally, this fern often grows on open, exposed headlands near the ocean as well as exposed mountain tops. This is a mid-sized, deciduous clumping fern reaching about 2 feet and is hardy to zone 4. Perhaps in warmer climates you would be better to grow the southern lady-fern, A. asplenioides as it is better able to cope with sun and heat (again assuming the soil stays moist).

Above is the typical lady fern while below are some of the more interesting cultivars 'Frizelliae' and 'Victoriae'

The common ostrich fern, Matteucia struthiopteris, is reputed to be very sun-tolerant. I grow mine in full sun but then I don't have the excessive heat of more inland areas of North America. I expect that a little shade from the hottest time of the day might be advised in warm areas. Few ferns are as architectural. The tall ( to 5 feet), narrow, vase-like habit and bright green color is superb. At times this fern will run and produce new plants at varying distances from the parent so has the potential to be a bit of a pest, but generally it is easy to control. This zone 3 ferns is deciduous.

Ostrich fern earlier and later in the season

Both the male fern, Dryopteris filix-mas, and the scaly (golden) male fern, D. affinis, are among the most sun-tolerant of the evergreen fern species. Both are clumpers and can achieve a considerable size with fronds reaching 4 to 5 feet. The fronds are quite leathery and deep green. There are many named selections of species. Like the lady fern, many of these selections date back to the Victorian times. Both species are hardy to zone 4.

Male fern (left), the cultivar 'Cristata' (middle) and scaly male fern (right)

In the south, an excellent fern for moist sun is the southern shield fern, Thelypteris kunthii. They not only tolerate sun but can easily cope with high heat and humidity. This slow to moderate running fern is deciduous, disappearing in winter. The fronds reach 2 to 4 feet. Over time, the spreading habit of this fern will lend itself to be a suitable groundcover. They are only hardy as far north as zone 7.

Another good sun-tolerant fern for southern climates is the southern wood fern or Florida shield fern, Dryopteris ludoviciana. This fern is semi-evergreen with fronds reaching to 4 feet. It slowly spreads to form a reasonable groundcover. It is a little hardier than the southern shield fern, being hardy to zone 6.

Southern wood fern (left) and southern shield fern (right)

Braken fern, Pteridium aquilinum, can certainly tolerate full sun and actually prefers sun to shade. It is with some reservation that I mention this species as it is very aggressive and rapid-spreading. From the rhizome arise large, individual, triangular-shaped fronds atop 2 to 5 feet stems. It is a deciduous species and can actually tolerate some drought. Use it in areas where its rambunctious nature will not out compete more timid neighbors. In fall, the fronds turn an attractive bronzy-brown. It is hardy through zone 3.

Details of the braken fern

There are a host of small semi-desert, evergreen ferns that are specifically adapted to sun and drought. These are the lip ferns, Cheilanthes spp. and cloak ferns, Notholaena spp. and Astrolepis spp. These are small tufted ferns with somewhat fuzzy, grey-green foliage. Cheilanthes have narrow fronds while Notholaena and Astrolepis are triangular in outline. All are generally under 30 cm. In the wild, Arizona is the place to see these ferns. In the garden, grow them in rock garden settings or xeriscapes. Most are hardy to zone 6 but require a rather dry climate (especially in winter) to thrive.

Examples of the semi-desert ferns include Cheilanthes tomentosa, C. lindheimeri and Astrolepis sinuata

As you can see, ferns are far more versatile than you would think. With their lovely foliage and forms, they can be used as a garden contrast in a wide variety of situations. Keep them moist and they will reward you in shade or sun.

I would like to thnak the following members for the use of their pictures: Cretaceous (Cheilanthes lindheimeri), Equilibrium (Osmunda claytoniana and Dryopteris filix-mas 'Cristata'), ericmg01 (Dryopteris filix-mas), gregr18 (Athyrium filix-femina 'Victoriae'), RonniePitman (Astrolepis sinuata), SecludedGardens (Matteuccia struthiopteris), weebles64 (Athyrium filix-femina 'Frizelliae'), wooffi (Dryopteris ludoviciana) and PurplePansies (closeup of Athyrium filix-femina).

About Todd Boland

About Todd Boland

I reside in St. John's, Newfoundland, Canada. I work as a research horticulturist at the Memorial University of Newfoundland Botanical Garden. I am one of the founding members of the Newfoundland Wildflower Society and the current chair of the Newfoundland Rock Garden Society. My garden is quite small but I pack it tight! Outdoors I grow mostly alpines, bulbs and ericaceous shrubs. Indoors, my passion is orchids. When not in the garden, I'm out bird watching, a hobby that has gotten me to some lovely parts of the world.


Plant Finder

Interrupted Fern features bold spikes of brown flowers rising above the foliage in mid summer. Its enormous oval bipinnately compound leaves are lime green in color. The foliage often turns tan in fall. The fruit is not ornamentally significant.

Interrupted Fern is an herbaceous fern with a shapely form and gracefully arching fronds. Its relatively fine texture sets it apart from other garden plants with less refined foliage.

This is a high maintenance plant that will require regular care and upkeep, and is best cleaned up in early spring before it resumes active growth for the season. Gardeners should be aware of the following characteristic(s) that may warrant special consideration

Interrupted Fern is recommended for the following landscape applications

  • Accent
  • Groundcover
  • Naturalizing And Woodland Gardens
  • Bog Gardens

Interrupted Fern will grow to be about 4 feet tall at maturity, with a spread of 4 feet. When grown in masses or used as a bedding plant, individual plants should be spaced approximately 3 feet apart. It grows at a fast rate, and under ideal conditions can be expected to live for approximately 15 years.

This plant performs well in both full sun and full shade. It prefers to grow in moist to wet soil, and will even tolerate some standing water. It is not particular as to soil type or pH. It is somewhat tolerant of urban pollution. Consider applying a thick mulch around the root zone over the growing season to conserve soil moisture. This species is native to parts of North America. It can be propagated by division.


Medicinal Benefits of Ferns

The Lenni Lenapes and Iroquoians are natives to the Delaware River valley region. The natives as well as the Cherokees used the many available species of ferns for medicinal benefits.

Native American medicinal uses of ferns can be categorized into five major groups, seen below. When a fern species is listed more than once, the Latin name is only used the first time. Some additional uses, such as Cinnamon Fern’s use for snakebite and Maidenhair’s use for heart trouble, go unmentioned in order to keep this list simple, easy to read, and memorable.

Ferns used for Rheumatism

Maidenhair (Adiantum pedatum) used for rheumatism.

Marginal Wood Fern (Dryopteris marginalis) used for rheumatism.

Sensitive Fern (Onoclea sensibilis) used for arthritis.

Cinnamon Fern (Osmunda cinnamomea) used externally for rheumatism and internally for joint pain.

Christmas Fern (Polystichum acrostichoides) used for rheumatism.

Bracken Fern (Pteridium aquilinum) used for rheumatism.

Ferns used for Lungs

Maidenhair smoked for asthma.

Maidenhair Speenwort (Asplenium tricomanes) used for coughs.

Rattlesnake Fern (Botrychium virginianum) used as a cough medicine for tuberculosis.

Hay-scented Fern (Dennstaedtia penctilobula) used for chills and lung hemorrhages.

Rock Cap (Polyopdium virginianum) used for sore throat, colds, measles, tuberculosis, cough, and lung congestion.

Christmas Fern used for chills, fever, pneumonia, red spots on skin, listlessness, tuberculosis, and hoarseness.

Bracken Fern used for tuberculosis, infections, and chest pain.

Ferns used for Gynecology (including menstrual, postpartum, and breastfeeding)

Walking Fern (Asplenium rhizophyllum) used topically and as emetic for swollen breasts.

Maidenhair Speenwort used for irregular menses and breast diseases.

Lady Fern (Athyrium filis-femina) used for mothers with intestinal fevers and to prevent water breaking.

Mountain Wood Fern (Dryopteris campyloptera) used for disease of the womb.

Ostrich Fern (Matteuccia struthiopteris) used as decoction of sterile leaf stalk base for the expulsion of afterbirth and for back pain.

Sensitive Fern (Onoclea sensibilis) used for infection, blood disorders (blood deficiency, cold in the blood, and others), and to restore the female system after childbirth. Externally used for sores.

Cinnamon Fern used for women’s troubles, caked breasts, and malaise.

Interrupted Fern (Osmunda claytoniana) used for weak blood and gonorrhea.

Royal Fern (Osmunda regalis) used for menstrual problems.

Bracken Fern used for weak blood, uterine prolapse, suffering after birth, caked breast, weakness, and headaches.

Marsh Fern (Thelypteris palustris)used as a gynecological medicine.

Ferns used for the Blood

Maidenhair used as a wash or poultice for bleeding.

Lady Fern used for vomiting of blood.

Hay-scented Fern used for lung hemorrhages.

Sensitive Fern used for blood deficiency, cold in the blood, and other blood disorders.

Christmas Fern used for weak blood and toxic blood.

Interrupted Fern used for weak blood.

Bracken Fern used to make good blood after menses or childbirth.

Ferns used for Digestion (including stomach ache and parasites)

Mountain Wood Fern used for stomachache.

Crested Wood Fern (Dryopteris cristata) used root infusion for stomach trouble.

Royal Fern used for intestinal worms.

Rock Cap used for stomachaches and cholera.

Christmas Fern used for stomachache, bowel problems, toothache, cramps, and diarrhea.

Bracken Fern used for diarrhea, nausea and vomiting, infections, diarrhea, weakness, stomach cramps, and headaches.

Sensitive Fern used for intestinal troubles.

Four common ferns

Maidenhead - Adiantum pedatum

Grows in North America and East Asia.

Rattlesnake Fern (Botrychium virginianum)

United States, in the mountains of Mexico, in Australia, in some parts of Asia, as the Himalaya Mountains, and is found also in Norway, in the Karelia region of Finland and Russia, and around Gulf of Bothnia, although in no other part of Europe.

Ostrich Fern (Matteuccia struthiopteris)

Also known as fiddlehead ferns or shuttlecock fern, is a crown-forming, colony-forming fern. It grows in temperate regions of the Northern Hemisphere in central and northern Europe, northern Asia, and northern North America.

Bracken Fern (Pteridium aquilinum)

Also known as 'eagle fern', Bracken Fern a species occurring in temperate and subtropical regions in both hemispheres. The extreme lightness of its spores has led to its global distribution.


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