Even though you can’t grow many ornamental roses or giant chrysanthemums in shady parts of your yard, shade beds don’t need to be bland or empty. Ferns add a lush, jungle-like feel to temperate gardens and need practically zero maintenance.
Their lacy appearance and mystical bright green fronds are particularly valuable additions to bare soil beneath trees or the east and north-facing borders of your house. These no-fuss ferns are native to North America and ask for little more than regular moisture and protection from direct sunlight. They also make nice houseplants!
Sword ferns are the most abundant wild ferns along the West Coast and are easily recognizable by their long, dark green fronds that grow in radial clumps. If you want to add this verdant textural undergrowth to your landscape without adding to your maintenance needs, here is everything you need to know about growing sword ferns.
‘Polystichum munitum’ Plant Overview
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History and Cultivation
Ancient ferns reproduced through spores before flowering plants dominated.
Ferns are fascinating plants that have covered massive landscapes of our planet for hundreds of millions of years. Fossilized ferns date back to the Paleozoic era, more than 360 million years ago! Their frilly-toothed fronds have a mystically ancient appearance that may remind you of Jurassic Park.
That’s because ferns and coniferous trees were the dominant plants during the age of the dinosaurs. In fact, ferns are theorized to be the favorite food of legendary herbivorous dinosaur species like triceratops and stegosaurus.
As some of the most primitive plants on Earth, ferns thrived for over 100 million years before flowering plants (angiosperms) evolved. Flowering and seed-producing plants now dominate the botanical world. But long before seeds developed, ferns spread their progeny via spores. In the summer, you can find the intriguing fuzzy round growths of sori (spore cases) arranged on the underside of fern fronds.
What is Sword Fern?
Striking sword ferns produce evergreen fronds and adapt to diverse environments.
Botanically known as Polystichum munitum, sword ferns are evergreen or semi-evergreen perennial plants with deep green fronds up to 4 feet long. The pinnately compound fronds include sharp-toothed leaflets shaped like swords. Also known as western or California sword fern, these gorgeous ancient plants cover forest floors, river edges, wetlands, and shady hills throughout the western United States, from Alaska to Mexico.
The shade-loving clumps thrive in moist environments with partial to full shade and are popular ornamentals in moist landscapes. They particularly thrive in wet coastal environments beneath the branches of coniferous trees, but the species is also adapted to inland areas of Idaho, Montana, and South Dakota.
The genus name Polystichum comes from the Latin word poly, meaning “many,” and the Greek stichos, meaning “rows.” This refers to the rows of fuzzy yellow-orange spores that develop on the undersides of fronds. The species epithet munitum translates to “armed with teeth,” describing the toothed edges of the fronds.
Can You Grow Them as a Houseplant?
In zones 3 and colder, they may be brought indoors during winter.
Western sword ferns (Polystichum munitum) are sometimes grown as houseplants or in terrariums. They are known for their easygoing, low-maintenance cultivation but should not be confused with the Australian sword fern, Nephrolepis obliterata, or the wild Boston sword fern, Nephrolepis exaltata. Western sword ferns are native to forested areas of the western United States, but Australian sword ferns originate in Australia, and so-called “wild” Boston sword ferns hail from Florida.
Some gardeners grow them in pots to bring indoors in the winter in zones 3 and colder, but this isn’t typically necessary in zones 4 through 9. These ferns serve as large, cold-hardy perennial groundcover plants in an outdoor landscape but can be dwarfed to fit in an indoor container. They require continuous moisture and humidity to retain their gorgeous deep green color.
Propagation
What differentiates ferns from most of our garden plants is they cannot be grown from seed because they don’t produce seeds or blooms! Instead, ferns spread by spores. These plants evolved this reproductive technique long before flowers even existed on Earth.
However, spore propagation is less common because it takes a lot of patience, and mature plants are widely available in nurseries. The plants can also be replicated via rhizome divisions or plantlets.
Spores
Collecting sword fern spores in late summer is non-harmful and not disruptive.
Spore propagation is a fascinating science project, but beware that it requires ample patience and time. It takes several months for spores to develop into young fiddleheads and up to 2 years to reach the transplanting stage.
If a friend already has a mature sword fern or you’ve identified one in a nearby forest, you can collect spores from the undersides of the fronds in late summer. While we usually don’t advocate for collecting native plants from the wild, sword fern spores are an exception because collecting the spores does not harm or disrupt the plant.
So long as you are gentle with the fronds, gathering the dusty little orangish-brown spores from the symmetrical dots under the leaves is very easy and intriguingly fun. Of course, you should never dig up, prune, or cut a wild plant unless it grows on your own property.
To collect sword fern spores:
- Collect and germinate spores in late summer.
- Identify mature fronds with sporangia (spore cases) on the underside of the leaves.
- The sporangia are yellowish-orange to brown circular dots arranged under the fronds.
- Mature sporangia are powdery and elevated in a rounded, erect shape.
- Hold a paper bag under the frond and gently shake it so the spores fall in the bag.
- Ideally, you should germinate them right away. If not, store in an airtight glass container in the refrigerator until you’re ready.
To germinate the spores:
- Clean several 4-6 inch pots with hot, soapy water.
- Sterilize with a diluted bleach solution (1 part bleach to 9 parts water) and let dry.
- Fill the pots with moistened unused peat moss. Peat moss is perfectly acidic for ferns.
- Gently sprinkle the spores on top of the peat.
- Do not cover with a potting medium. Leave the spores on the surface.
- Mist the surface with water and place a clear plastic dome or bag over the pots.
- Continuous moisture and high humidity are essential.
- Place in indirect light near a west or east-facing windowsill.
- Maintain temperatures between 60 and 85°F. Room temperature is great.
- The medium should stay moist but not soggy wet. Occasionally wipe down the dome to prevent excessive condensation.
After a few weeks, you should see a heart-shaped gametophyte form. This holds the eggs and sperm, which will combine to produce the sporophyte or the baby fern. Keep the gametophytes moist by occasionally misting them. Wait a few more weeks for the little fern fronds (sporophytes) to unfurl. The gametophyte will die off as the fern develops.
Gradually remove the dome or plastic bag as the fiddlehead opens. When the baby fern has a few fronds, use a popsicle stick or spoon to scoop up the tiny ferns with a bit of peat moss attached to their roots. Be very careful not to disturb them as you transfer to a larger container. Wait one to two seasons before transplanting into the garden.
Rhizome Divisions
In spring, effortlessly divide sword ferns using a shovel, ensuring well-established rhizomes.
Division is much more straightforward than spore propagation. All you need is a mature fern, a shovel, and gloves! Sword ferns grow from rhizomes or flexible branched appendages that form dense fibrous masses of roots.
It’s best to divide rhizomes in the spring after the risk of frost has passed. Be sure the rhizome is well-established and the fern has many healthy, big fronds.
To divide a Western sword fern:
- In the spring, use a shovel to dig up the entire plant.
- Preserve as much of the root system as possible by digging 6-12” from the center point.
- Brush away the soil to get a good look at the root mass.
- Use your hands or sharp, sanitized pruners to separate the rhizome into smaller sections.
- Ensure each division has both fronds and roots attached to it.
- Replant each division in a new location or pot.
- Water consistently until established. Don’t let them dry out!
Plantlets
Sword ferns often produce plantlets that emerge near the base.
Sometimes, sword ferns produce little plantlets near the base of a mother plant. They emerge near the root clump and grow as an exact clone of the original plant. Once the plantlet is a few inches tall and has its own root system, you can use a sharp knife or pruners to remove it from the mother plant.
Ensure you dig up enough of its roots to sustain it in a new location. Move the plantlet 2-4 feet from the mother plant or into a container filled with peat moss-rich soil. Water thoroughly until established.
Planting
The best time to transplant these pretty native ferns is in the early spring or the fall. Mild temperatures and abundant moisture are key to effective establishment. Planting in the summer is not ideal because the heat can stress the plants and potentially lead to transplant shock.
How to Transplant
For successful transplanting, choose early spring or fall, avoiding the summer heat.
Whether you purchased a sword fern from a nursery or propagated one yourself, the transplanting process is very straightforward. The rhizomes are durable and easy to move as long as you preserve as much of the root mass as possible.
To transplant:
- Choose a partially to fully shaded location with acidic, well-draining soil and plenty of organic matter.
- Amend with peat moss and clear any weeds.
- Dig a hole about the same depth as the root ball and 2-3x wider than the existing roots.
- Grasp the potted plant from its base and massage the roots out of the container.
- If transplanting from the ground, carefully dig around the fern 2-3 feet from the center clump.
- Position the fern in your hole, making sure the top of the root ball is level with the soil surface.
- Avoid burying the top of the clump deeply in the soil.
- Backfill with surrounding soil and water generously to help it get established.
- Add a layer of leaf litter or bark mulch to retain water and suppress weeds.
Spacing
Optimal spacing caters to your desired aesthetics—closer for lush density, wider for ornamental emphasis.
Mature ferns can reach up to 4 feet in width. Space sword ferns 2 to 4 feet apart to allow enough room for growth. Closer spacing is better for a lush, dense planting like a forest garden floor, while wider spacing is ideal for large centerpiece plants in an ornamental landscape.
How to Grow
It’s hard to find a more easygoing plant than a sword fern. This ancient species has thrived on Earth for hundreds of millions of years before humans even existed! It can certainly fend for itself in the garden if you provide conditions that mimic its native habitat.
Light
Ferns prefer partial to full shade, growing best under coniferous trees or buildings.
Partial to full shade is ideal for ferns. They don’t do very well in bright, direct sunlight unless they’re in the far northern reaches of their range. If you live in a mild or warm climate, shade is necessary.
Scatter plants beneath the canopy of coniferous trees such as pine, fir, Douglas fir, and hemlock. They can also thrive under oak and alder trees. The dappled light through the trees provides the perfect amount of photosynthetic power for these attractive ferns. You can also plant them along the eastern and northern sides of a building.
Too much sunlight can burn the delicate fronds, so avoid prolonged periods of full sun. The deep green color may turn pale or brown if exposed to excessive light. When growing indoors, keep them away from southern exposure windows.
Water
In containers, avoid overwatering to prevent rot issues, especially in peat-moss-based soil.
Consistently moist soil ensures that fronds stay perky and happy. They enjoy a soil moisture level similar to a wrung-out sponge, never too dry but never waterlogged. You’ll probably never need to water your sword ferns in areas with regular rainfall. However, the plants often need supplemental watering during establishment, especially if you are experiencing a dry spell.
Once the roots are anchored, sword ferns are relatively drought-tolerant as long as they grow in a cool, shady area with plenty of organic matter in the soil. A layer of leaf mulch, pine needles, or bark mulch is ideal for replicating the rich upper soil layers of a forest floor.
If growing in a container, be sure not to overwater. Standing water and waterlogging can cause issues with root rot fungi or algae growth. Always stick your finger in the soil to check the moisture before adding more. If growing in a peat-moss-based soil blend, thoroughly hydrate the soil before planting because peat moss can be hydrophobic (water-resistant) in its dry packaged state.
Soil
Create an ideal environment for sword ferns with acidic, well-drained, organic-rich soil.
Acidic, well-drained soil rich in organic matter is ideal for this native plant. If you have ever been to the Pacific Northwest or the coasts of northern California, you may have noticed how the forest floors are covered in plant debris, creating a moist, rich foundation for ferns to grow.
A pH between 5.5 and 6.5 is ideal. Coniferous tree needles help naturally acidify the soil, but you may need to amend regular neutral garden soil with sulfur to lower the pH. Peat moss amendments are also helpful for acidifying the soil.
Drainage is crucial, as sword ferns will not do well in compacted or waterlogged soil. If you have heavy clay, it’s best to break it up and mix in lots of organic matter, like leaf debris and bark, before planting.
Climate and Temperature
In colder regions, they shed fronds in winter, sprouting new growth in spring.
Sword ferns are adapted to USDA zones 4 through 9. In warmer climates, they remain evergreen year-round. In the colder parts of their range, they may drop their fronds in the winter and return with new growth in the spring. Fiddleheads are adorable curly-que-shaped young fronds that appear in the spring and unroll into full-size leaves. They are popular amongst foragers for eating.
Fertilizing
Native sword ferns grow well without fertilizer, relying on organic soil nutrients.
Like most native plants, this species doesn’t need any fertilizer! As long as the soil has organic matter like decaying leaves, the fern can make its own food and scavenge minerals from the native soil. In a pot, you may need to add compost or a diluted slow-release all-purpose fertilizer once per year. Excessive fertilization can burn fern fronds, so be very gentle.
Maintenance
Young sword ferns need consistent moisture for robust rhizome development.
Young plants need regular moisture to develop strong rhizomes. Once a sword fern is established, virtually no maintenance is required. In a manicured landscape, you may wish to remove older leaves that have died back, but it’s unnecessary. In fact, the fern naturally mulches itself with expired fronds, so I like to let them do their own thing.
Of more than 20,000 species of ferns worldwide, the western sword fern is among the most recognized. It has many names, but Polystichum munitum is the most reliable because common names can get confusing.
The popular houseplants, Australian sword fern, Nephrolepis obliterata, and wild Boston sword fern, Nephrolepis exaltata, are only distantly related to western sword fern and have key distinguishing characteristics:
Australian Sword Fern (Nephrolepis obliterata)
This fern, unrelated to the Western sword fern, hails from Australia.
While the Australian sword fern shares the same “sword-like” leaves, this tropical fern is unrelated to the Western sword fern. It is in the family Lomariopsidaceae and is native to Australia.
These ferns enjoy brighter, indirect light and are only outdoor hardy in USDA zones 9 through 11. It can be grown as a houseplant with plenty of humidity. Sometimes called Kimberly Queen ferns, these compact ferns average 3 feet tall in containers.
Wild Boston Sword Fern (Nephrolepis exaltata)
Unlike what the name suggests, the “wild” Boston sword fern isn’t from Boston and doesn’t grow wild across the U.S.
To make matters more confusing, the so-called “wild” Boston sword fern is not from Boston, nor does it grow wild in most of the U.S. It is in the Lomariopsidaceae and native to humid tropical forests of Florida, Mexico, South America, and the West Indies.
It can grow up to 7 feet tall in tropical climates but averages about 3 feet tall and wide in hanging baskets or containers. The growth habit is upright and erect in contrast to the Western sword fern’s arching appearance. If you live in a temperate climate, this fern is less reliable when grown outdoors.
Design Ideas
Western sword ferns thrive with plants that enjoy shaded woodland settings and acidic soil. They grow well under native coniferous trees like fir, pine, and hemlock. These companions will complement the aesthetics and low-maintenance care of a fern planting:
Hostas (Hosta spp.)
Opt for variegated types to contrast with the fern’s dark green fronds.
These versatile plants provide a gorgeous ground cover near sword ferns. I especially love the light green variegated types that contrast against dark green fronds. Hostas enjoy slightly acidic soil rich in organic matter, just like their fern friends. Pair these together for a magical forest fairy feel in your landscape.
Coral Bells (Heuchera spp.)
Beloved coral bells, with ruffly heart-shaped leaves, thrive alongside ferns in zones 4-9.
Known for its ruffly heart-shaped leaves, coral bells are low-maintenance perennials that thrive in similar conditions to ferns. Hardy in zones 4-9, they readily endure cold winters and well-drained soil rich in humus. Try dark-foliage varieties like ‘Black Pearl’ or ‘Forever Purple’ for an intriguing color balance with ferns.
Trilliums (Trillium spp.)
With distinct three-petaled flowers appearing in early spring, they thrive in partially shaded, moist conditions.
These pretty forest-dwelling flowers are a native woodland plant that grows alongside western sword ferns in the wild. They have distinctively three-petaled flowers that appear in early spring. Partially shaded, moist, forested conditions are perfect for trilliums.
Rhododendrons (Rhododendron arboreum)
These flowering shrubs add a vibrant burst of pink in summer, complementing fern plantings.
Rhodies famously enjoy acidic soil, much like western sword ferns. These flowering native shrubs provide a nice backdrop to fern plantings, adding a glorious burst of pink color in the summer.
Choose a variety native to your region of the U.S., such as R. macrophyllum in the Pacific Northwest, R. maximum in the Eastern states and Appalachian mountains, and the stout R. carolinianum in the southern states.
Pests and Diseases
This wild native plant is virtually pest-and-disease-free, but a few issues may arise if it gets stressed in cultivation.
Aphids
Consider diluted neem oil or horticultural soap for indoor plants if the infestation persists.
These little sap-sucking bugs have no mercy for any plants in the garden. If you notice them on your ferns, it’s usually no big deal. But if they get out of hand, spray the plant down with a heavy blast of water. Indoor plants may need a treatment of diluted neem oil or horticultural soap.
Fern Mites and Mealybugs
Treat indoor ferns for mites or mealybugs with neem oil or horticultural soap.
Little mites and mealybugs are almost indistinguishable with the naked eye. They are most commonly an issue with indoor houseplant ferns.
The best treatment is neem oil or horticultural soap. These bugs may appear scattered on the leaf surface and should not be confused with the orderly spore spots appearing on the underside of fronds in the summer.
Foliar Nematodes
These microscopic worm-shaped nematodes are not the kind you’re likely to find in your veggie garden. Instead, these dwell on the fern’s fronds and feed on them as well as emerging fiddle leaves. As they feed, they leave browned areas that darken over time and eventually die. Infestations can cause foliar collapse. They are most common on indoor plants.
Good hygiene is the key to preventing the spread of these pests. Don’t propagate from plants that have been infested. Remove distorted fronds, and quarantine plants that you know have nematodes. No commercially available treatment options exist, so prevention is your only defense.
Leaf Spot
Remove affected leaves on sword ferns to combat leaf spots, distinguishing them from spore cases (shown above).
Due to its love of moist environments, Taphrina faulliana fungi sometimes attack sword ferns. Leaf spots caused by this pathogen can appear in many shapes and sizes, from circular to oval, white to green, and small to large blisters. They cause areas of the fronds to decay, ooze, or drop off.
Be sure you don’t confuse them with the symmetrical rows of sori (spore cases) on the undersides of leaves. Leaf spot diseases often appear scattered and concentrated on one part of the plant.
The best thing you can do is remove and destroy affected leaves. In extreme cases, an organic copper fungicide may be warranted to prevent the spread to other plants. Avoid overhead sprinkler irrigation that causes prolonged wetness on the leaf surface. When propagating, practice quality sanitation of shears and tools with a diluted bleach solution.
Plant Uses
Western sword fern is a shade-loving species that enhances woodland and ornamental beds.
In the garden, this plant is mostly used as a shady species for clump plantings or unique specimens in woodland gardens and ornamental beds. The fiddleheads (young emerging unfurled fronds) are sometimes foraged for eating.
Western sword fern is an important plant in native western forests, providing erosion control, ground cover, and wildlife habitat. Sword ferns are an important nesting and cover material for native birds, small mammals, and deer.
In the wild, black bears collect the fronds for winter hibernation dens. Mountain goats and elk eat the leaves, but don’t worry—planting these ferns in your garden should not attract bears or elk!
Final Thoughts
This fern is ridiculously easy to grow and provides lush ground cover for any shaded area in your landscape. Be sure the area is protected from direct sunlight and the soil is well-drained and moist. Don’t forget to admire the uniquely fuzzy rows of spores on the underside of the fronds each season. Kids love to observe and learn about the unique sporulating structures.
