Cinnamon Fern (Osmundastrum cinnamomeum)

Cinnamon Fern

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Osmundastrum is the common name for a genus containing a single species, O. cinnamomeum, commonly known as the “Cinnamon Fern.” These handsome plants can typically be found residing in wet, rich soils in forested or swampy areas. This species’ common name derives not from its scent or its edibility, but rather its color; vivid green spore-bearing fronds slowly become brown, or cinnamon-colored, as summer turns to autumn. 

I. Appearance and Characteristics 

Osmundastrum is a genus of leptosporangiate ferns in the family Osmundaceae with one living species, Osmundastrum cinnamomeum, the cinnamon fern. It is native to the Americas and eastern Asia, growing in swamps, bogs and moist woodlands.

In North America it occurs from southern Labrador west to Ontario, and south through the eastern United States to eastern Mexico and the West Indies; in South America it occurs west to Peru and south to Paraguay. In Asia it occurs from southeastern Siberia south through Japan, Korea, China and Taiwan to Myanmar, Thailand and Vietnam. Osmundastrum cinnamomeum has a fossil record extending into the Late Cretaceous of North America, approximately 70 million years ago, making it one of the oldest living plant species. The fossil records of the genus extend into the Triassic.

Osmundastrum cinnamomeum is a deciduous herbaceous plant that produces separate fertile and sterile fronds. The sterile fronds are spreading, 30–150 cm (0.98–4.92 ft) tall and 15–20 cm (5.9–7.9 in) broad, pinnate, with pinnae 5–10 cm (2.0–3.9 in) long and 2–2.5 cm (0.79–0.98 in) broad, deeply lobed (so the fronds are nearly, but not quite, bipinnate). The fertile spore-bearing fronds are erect and shorter, 20–45 cm (7.9–17.7 in) tall; they become cinnamon-colored, which gives the species its name. The fertile leaves appear first; their green color slowly becomes brown as the season progresses and the spores are dropped. The spore-bearing stems persist after the sterile fronds are killed by frost, until the next season. The spores must develop within a few weeks or fail.

The Osmundastrum cinnamomeum fern forms huge clonal colonies in swampy areas. These ferns form massive rootstocks with densely matted, wiry roots. This root mass is an excellent substrate for many epiphytal plants. They are often harvested as osmunda fiber and used horticulturally, especially in propagating and growing orchids. Cinnamon Ferns do not actually produce cinnamon; they are named for the color of the fertile fronds.

Cinnamon Fern (Osmundastrum cinnamomeum)

II. How to Grow and Care

Light & Temperature

These shade loving plants naturally prefer a wooded setting, but they can tolerate sun (even full sun) if they are standing in water. In areas with only moist or damp soil, these ferns require partial to full shade.

 

Cinnamon Osmunda Fern is winter hardy in USDA hardiness zones 3 through 9.

Watering & Feeding

These swamp loving plants require a great deal of water. It’s best to grow them in soil that is rich in organic compost for consistent, continuous feeding.

Soil & Transplanting

These hardy native ferns do very well in acidic wet soil that is rich in humus. Mud, sand, sandy loam, clay, clay loam and calcareous soils are all acceptable. The pH level should be 6.8.

Grooming & Maintenance

Keep your ferns healthy and strong by removing dropped and dead leaflets and fronds as needed. This will help prevent problems with fungal development while maintaining a tidy appearance.

Propagation

Cinnamon ferns can be propagated from spores, divisions, or transplants, which are ordered here in descending difficulty.

From Spores

This is the toughest propagation method on this list, but also the most rewarding.

Ferns go about reproduction a bit differently than seed-producing flora, and their fascinating life cycle is definitely worth rehashing

Beneath the pinnae of fertile fronds are sori, which contain spore-producing structures known as sporangia.

These organs drop their spores, which float away on the wind, land, and eventually germinate into prothalli, which create egg and sperm cells within themselves.

Fertilization occurs, baby ferns emerge from the prothalli, and the circle of life continues.

O. cinnamomeum drops its spores from May to June, so make sure to leave a note in your gardening journal and check your calendar. During this time, cut away a fertile frond from the rest of the plant.

To the best of your ability, since these are prone to scrunching up and curling, spread the frond flat atop a clean sheet of paper before draping a second sheet on top of the frond.

Leave your frond-on-paper sandwich somewhere indoors where it won’t be disturbed by drafts or nosy roommates. About 24 hours later, check for dropped spores.

If they’ve dropped successfully, you should see spores on the paper in the pattern of the frond. If not, they’ll appear faint or they’ll be missing entirely, which indicates that you harvested the frond either too early or too late.

Collect the spores in an envelope and place it in the refrigerator. Spores can be sown in any season and they’ll last for years in the refrigerator, so take your time in deciding when you want to use them!

Then fill a three- to four-inch pot with an equal mix of sphagnum peat moss and perlite – the former for moisture retention, the latter for drainage.

Tamp down the surface, water well, then spread a match-head-sized amount of spores across the soil surface.

Seal the pot in a gallon-size zip-top plastic baggie before placing it on a sunny windowsill that – if you’re in the Northern Hemisphere – faces east in summer or south in winter.

Maintain soil moisture and indoor temperatures of 65 to 75°F throughout this process.

Green prothalli should form on the soil surface in several weeks’ time. To stimulate fertilization, open the bag and mist them when they reach a quarter-inch in height, then zip it back up.

No baby ferns after three months? Dilute a proper dose (according to instructions) of liquid houseplant fertilizer down to quarter-strength by adding three parts water per one part fertilizer, then apply it to the potting medium. Reapply once every three months.

After the baby ferns emerge and grow an inch or two tall, separate them into clumps of two or three.

Each clump should be transplanted into its own pot filled with the same medium described above, or into a large tray with two inches of space between each.

Either bag the containers up or put them in a terrarium where warm and humid conditions can be maintained. In two weeks, unzip the baggies or leave the terrarium lid ajar so the plants can start to acclimate to less humid conditions.

Nine months post-sowing, the plants should be ready to harden off.

On a spring day when the risk of frost has passed, leave the baby plants outside in partial to full shade for 30 to 60 minutes before bringing them back indoors.

Add 30 minutes to a full hour of outdoor exposure on each successive day until the baby ferns can last a full day outside, at which point they’ll be ready to transplant into the garden.

From Divisions

Dividing a mature fern should occur every three to five years, on average. If you simply want additional plants, then that’s reason enough to divide.

But once you notice that the center of your fern is dead, or that frond growth is smaller than normal, division becomes quite necessary.

In early spring or right after the first frost in fall, deeply irrigate the cinnamon fern that you intend to divide.

Cut the fronds back to half a foot above the ground, then dig a circle around the plant spaced four to six inches away from the outermost fronds with a shovel, spade, or garden fork.

Lever the plant out of the ground with your digging implement, remove any loose soil from the roots, then put the to-be-divided fern on a tarp so you can easily keep track of your divisions.

Slice the root ball into daughter plants of equal size. Four divisions is a solid amount, but more or less than that is all good. Once you have your divisions, it’s transplanting time!

By Transplanting

If you had access to a mature plant and followed either of the above propagation methods correctly, you should have some O. cinnamomeum ready to go.

Dig holes big enough for the root systems of your transplants. Plop the transplants in the holes, use the dug-out soil for backfilling, and then deeply water the transplants. Keep the soil moist.

Pests and Diseases

  • Herbivores

There’s not much to worry about when it comes to our furry, flora-munching friends. Especially deer and rabbits – cinnamon ferns are quite resistant to them.

  • Common Pests

Managing insects also works to manage disease, since bugs can vector pathogens between different plantings. But when it comes to O. cinnamomeum, there’s only one major creepy-crawly worth worrying about…

Osmunda Borers

Also known as Papaipema speciosissima, the Osmunda or regal fern borer moth has a wingspan one-and-a-half to two inches long, and a fuzzy orange and grayish-brown body.

The forewings are orange and striped, with two reflective notches each, while the rear wings are a grayish-brown with rusty, reddish markings.

These pests produce larvae that bore into the roots of ferns such as O. cinnamomeum in summer after a period of overwintering in nearby soil or plant detritus.

This root boring obviously damages said roots, along with causing problems above the soil line such as frond wilting, yellowing, and overall stunted growth.

Along with clearing away any plant detritus, dusting diatomaceous earth around the root zones of your cinnamon ferns can help to prevent larval boring.

  • Common Disease

Sterilizing garden tools, propagating from healthy plants, and using pathogen-free soil are all easy and effective methods of preventing disease occurrence.

Crown and Root Rot

Whenever an O. cinnamomeum is sitting in soil that doesn’t drain well, its roots can become waterlogged.

Excessive moisture prevents the roots from taking up enough oxygen, which leads to stunted growth, necrotic crowns and roots, wilting, and/or chlorotic foliage.

Additionally, certain pathogens love wet conditions such as oversaturated soil. Such environments encourage their presence and subsequent infection.

There’s not much you can do reactively besides pitching infected and rotted-out plants, so it’s best to focus on prevention.

Avoiding overwatering and ensuring that the soil is well-draining are the two most important things that you can do to prevent rot.

III. Uses and Benefits 

  • Ornamental uses

As an ornamental Fern, Osmunda is an excellent choice to adorn wet areas surrounding streams and ponds. It does well in water gardens and in swampy areas.

It can make a nice shaded border and is a good addition to woodland gardens and shaded wildscaping projects.

Cinnamon Fern is tolerant of heavy shade and the presence of rabbits. It can be planted successfully under and around Black walnut trees.

The plant is very attractive to birds, who like to use the fuzzy covering of young fiddleheads as nesting material.

  • Culinary uses

The fiddleheads can be eaten raw, added to salads or sautéed with onion, garlic and butter for an asparagus-like dish.

The latent buds are also edible and can be eaten raw early in the springtime. They are said to resemble chestnuts in both flavor and appearance.

  • Medicinal uses

The Iroquois and Cherokee tribes used the fern for a wide variety of medicinal purposes including as a cold remedy, gynecological aid, venereal aid, and as a remedy to snake bites.

Cinnamon Fern (Osmundastrum cinnamomeum) Details

Common name

Cinnamon Fern

Botanical name

Osmundastrum cinnamomeum

Family

Osmundaceae

Species

cinnamomeum

Origin

Mountain, Piedmont, Coastal Plains

Life cycle

Plant type

Hardiness zone

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Sunlight

Maintenance

Soil ph

Drainage

Growth rate

Spacing

3 ft. – 6 ft.

Height

2 ft. – 6 ft.

Width

2 ft. – 6 ft.

Leaf color

,

Stem color

Brown, Copper

Leaf benefit

Garden style

Uses

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