Tall and green in the spring and summer and a stunning yellow in the autumn, cinnamon ferns are more than just a great showpiece. They are not fussy about high temperatures or humidity and are fairly hardy in the cold.
These pretty fronds are common across the Eastern U.S., filling the space under trees and near water. From the wilds of nature to the structure of a garden, these beauties are not picky about their environment as long as they have moisture and some protection from the harsh sun.
Ferns are great fillers for spaces under trees and near water where other plants fail to grow. In this article, we have all the tips you need to grow verdant cinnamon ferns and replicate them as often as needed.
Overview
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What Are Cinnamon Ferns?
This fern has distinctive cinnamon-colored fronds.
Osmundastrum cinnamomeum, previously called Osmunda cinnamomea is commonly known as cinnamon fern due to its cinnamon-colored fronds. The unique tannish-brown color covers the base and spikes of spores that grow in spring. These ancient woodland plants thrive in moist, boggy areas under the shade of trees and larger shrubs.
Native Area
Osmundastrum cinnamomeum remains genetically unchanged for 180 million years.
Cinnamon fern is native to a wide area along the southern and eastern half of the United States, from Florida to Canada, as well as several regions in Central America and the northern regions of South America.
In recent years, fossil evidence has unearthed several fern species, including Osmundastrum cinnamomeum, dating back 75 million years. DNA testing reveals that they closely match other fern species dating even further back to 180 million years. What is curious is that the species has not changed much genetically in all that time. Scientists speculate that this fern grows much like it did in the age of the dinosaurs and before!
Characteristics
In late spring, fertile leaves form spikes with cinnamon-colored spores.
Like most ferns, cinnamon ferns are considered perennials that grow lush and healthy in spring and summer and then die back in winter. Furry, cinnamon-colored fiddleheads form at the base.
In early spring, the fronds unfurl into long fern fronds that are yellowish green. They grow to around 40 inches long and about 10 inches wide. These are sterile leaves. The leaves are the widest in the middle and taper towards the ends. They form a circle from which the fertile spikes grow from the middle. In autumn, the leaves turn yellow before the plant takes a nap during winter. The autumn foliage of this fern is quite a beautiful sight to see!
During late spring, fertile leaves form in the middle of the plant. They develop into long spikes covered in capsules containing spores surrounded by tiny hairs. They start green and then turn cinnamon-colored with age and maturity. Once the spores are released, the spike dies down.
One distinguishing feature of this species is the little tufts of hair between the leaf and the stem underside, making them easily identifiable when the spore fronds are absent. The leaves on their own are very similar to a lot of other ferns.
These ferns grow in clumps from the horizontal rhizomatous and fibrous root system underground.
Planting
Ferns are ideal for wet, shady areas and erosion control.
Cinnamon ferns are used as a ground cover in wet shady areas and for stabilizing areas against erosion, particularly slopes. They are also deer-resistant, so they perform well in wild areas.
Growing in Pots
Grow in large pots with good drainage.
Cinnamon ferns can be grown successfully in pots, but make sure that the pots are big enough for these large ferns. Use good potting soil with added drainage materials like perlite, vermiculite, or coco coir. Make sure the container has enough drainage holes, and cover it with a few broken crocks or stones before adding the potting mix.
Once planted, potted ferns need extra watering. Check on them at least twice a week, and they will do better with a more scheduled feeding scheme two to three times in spring. Keep them in a shady position, sheltered from extreme cold. Container ferns do not do well with cold. Cover with fleece or frost cloth when needed.
How to Grow
Here is exactly what a fern needs to stay healthy and aesthetically-pleasing.
Light
Partial to full shade is required for the fern’s optimal growth.
This fern needs partial shade to full shade to perform well. It will take some sun in colder climates where the sun is not as harsh, but it must always be watered and damp to thrive.
Water
It thrives in moist areas.
The best places for this native plant include moist wooded areas, marshy or boggy areas, and locations where water collects on the side of ponds, lakes, and streams. The amount of moisture they get often determines how green or yellow the leaves will be. The more water, the greener the leaves.
Add a thick layer of mulch to conserve water. Check the soil moisture weekly to catch any dehydration issues before the leaves turn brown and brittle.
Soil
Ferns prefer well-drained soil with a pH level between 4 and 6.5.
Moist but well-draining soils are ideal. In nature, they would be under the canopy of trees, so they would benefit from the broken-down organic materials found naturally in these areas. Rich with plenty of organic materials like leaf mold is best but they do adapt quite easily to other soil types. They prefer a slightly acidic pH level between 4 and 6.5.
Temperature and Humidity
They tolerate various temperatures and survive cold by going dormant.
Cinnamon ferns have adapted to varying temperatures and are not affected by humidity. Their native range in the Eastern U.S. is very humid. They can handle the cold because the foliage dies while they preserve their root systems underground in the coldest seasons. The leaves of these tough plants only re-emerge when the spring weather warms up.
Fertilizing
Feed ferns in spring with a balanced slow-release fertilizer.
When planting, always add plenty of compost and organic materials like leaf mold; this should provide all the nutrients they need. However, in areas with less-than-ideal soil, it helps to feed them in spring as they begin their growth with a slow-release balanced fertilizer according to the manufacturer’s directions. Don’t overdo it, as ferns are quite sensitive to over-fertilizing. If your soil is somewhat fertile, diluting liquid fertilizer is a good idea.
Maintenance
Prune damaged leaves for fern maintenance.
Apart from regularly replacing mulch, all the maintenance they need is a tidying of any damaged or dying leaves. Cut them off with a sharp pair of secateurs.
Transplanting
For continued healthy growth, transplant ferns when the roots outgrow the container.
Container ferns can be transplanted into fresh pots when the plants touch the sides of the container.
Propagation
Propagate this fern by division for the best results, but if you have the time and patience, you can grow it from spores.
Division
Divide cinnamon ferns every 3-4 years in moist soil.
It’s best to divide the plants every 3-4 years in early spring. Water well the day before you intend to lift and divide them.
To divide cinnamon ferns, carefully dig up the plants, remove any excess soil, and divide their mass of fibrous roots and rhizomes into about 3-4 plants. You may need the help of a sharp knife or pair of secateurs, both sterilized to prevent any exchange of pathogens.
Replant each set of roots into well-prepared soil with added compost and organic materials. Once planted, water well.
Spores
Harvest and sow cinnamon fern spores for propagation in containers.
Normally, fern spores would be carried on the wind to make new babies somewhere else, but with time and effort, you can expand fern populations by sowing the spores. It’s a long and laborious process, so make sure you are up for it. At the end of the day, it’s very rewarding to grow a native plant this way.
Gathering Spores
Gather the fertile fronds between May and June. These are the spikes of cinnamon-colored fronds that are protected in the middle of the ferns and filled with capsules of spores.
Place the fronds on a sheet of white paper and cover with another sheet of paper in an area free of drafts. After 24 hours, you should have some dropped green or brown spores on the paper. If you can’t see them, you may have harvested the fronds too early.
Collect the spores and save them in an envelope to sow now or later. If you want to keep them for a while, place them in a refrigerator.
Sowing Spores
To sow the spores, fill a container, seed tray, or 3-4 inch pots with a mix of 1 part moist sphagnum peat moss and 1 part perlite for drainage. Tamp down the mix, then sow the spores evenly across the top.
Cover the container with a plastic bag to create an ecosystem and place it in a warm area to germinate. After several weeks you should see the beginnings of the prothallus, which is a short-lived stage of germinating spores. You should see a heart-shaped structure that provides water and nutrition for the developing sporophyte, the beginning of the baby plants.
You should have baby ferns in about three months. If not try and dose them with a diluted liquid plant food to stimulate growth. Once the little guys are about an inch or two long, they can be potted into individual pots to grow on in groups of three to four.
In around nine months, the plants will be ready to be hardened off to be planted outside. Leave them outdoors for a few hours each day, adding to the time as the days go on. When the babies have been out for a whole day, they will be ready to be planted out.
Common Problems
Water adequately to prevent leaf damage.
Make sure ferns are watered enough to stop the leaves from browning and crumbling due to lack of water.
Cinnamon ferns are not much bothered by pests and diseases, but the osmunda borer moth is worth mentioning.
Papaipema speciosissima, commonly called osmunda borer or regal fern borer, is found over large areas of the United States. It is a type of cutworm that feeds on ferns, including cinnamon ferns. They usually feed on the fronds until they are ready to become moths, rarely damaging entire plants.
Frequently Asked Questions
Technically, the emerging fiddleheads are considered edible. But it should be noted that some ferns, including this one, could result in a thiamine deficiency in humans. They are considered mildly toxic. Besides, there are better-tasting foods out there.
The cinnamon refers to the color of the fibers found at the base of the plants and the cinnamon-colored spikes that form in the center of the plants in early spring. The fibers were once gathered and used for potted plants. Called osmunda fiber, it was a favorite growing medium for epiphytic orchids, but it has become scarce and comes at an expensive cost.
It’s not necessary to prune cinnamon ferns, but you can shape them and prune away any dead leaves. When the foliage turns yellow in autumn, you can cut it down until spring. To enjoy the colorful fall display, leave the fronds to die back on their own.
No, they are quite slow, spreading from the underground rhizomes and sets of fibrous roots. To make a good showing, plant a few ferns and divide what you have in 3-4 years, or try growing from spores to increase populations.
Final Thoughts
Big and bold, luxurious ferns are what comes to mind with cinnamon ferns. They are tall impressive ferns for the right spot in the garden or containers. You can buy large lush ones in a nursery or buy bare-rooted ones ready for planting online.
