While they are most commonly found growing in moist, wooded areas, sword ferns are quickly becoming popular in the home garden as well. These interesting plants are easy to grow with sword fern care being just as simple.
I. Appearance and Characteristics
Polystichum munitum, the western swordfern, is an evergreen perennial fern native to western North America, where it is one of the most abundant ferns in forested areas. It occurs along the Pacific coast from southeastern Alaska to southern California, and also inland east to southeastern British Columbia, northern Idaho and western Montana, with disjunctive populations in northern British Columbia, Canada; the Black Hills in South Dakota, United States; and Guadalupe Island off of Baja California, Mexico. Western swordfern is known to have locally naturalized in parts of Great Britain and Ireland.
The dark green fronds of this fern grow 50 to 180 centimetres (1.6 to 5.9 ft) tall, in a tight clump spreading out radially from a round base. They are single-pinnate, with the pinnae alternating on the stalk. Each pinna is 1 to 15 centimetres (0.39 to 5.91 in) long, with a small upward-pointing lobe (a sword hilt, hence the name) at the base, and the edges are serrated with bristly tips on the serrations. Beyond the upward-pointing lobe, the pinnae are broadly linear in shape, usually with a gradual taper and curved slightly toward the distal end of the frond. Individual fronds live for 1.5 to 2.5 years and remain attached to the rhizome after withering.
When they emerge in spring, the fronds are doubled back on themselves and circinate (rolled up) only at the tip. The round sori occupy two rows on either side of the midrib of each pinna and are covered by a centrally-attached, umbrella-like indusium with fringed edges. They produce light yellow spores. In deep shade, fronds spread nearly horizontally but with increasing sun exposure grow more upright. In young plants the leaves are often paler green and have shorter pinnae.
The preferred habitat of this fern is the understory of moist coniferous woodlands at low elevations. It grows best in well-drained acidic soil of rich humus and small stones. It is very resilient and survives occasional droughts, but flourishes only with consistent moisture and it prefers cool weather.
In cultivation, it also responds well to regular, light fertilization. While this fern is a favored horticultural subject in western North America, it has proved difficult or impossible to cultivate satisfactorily in the eastern part of the continent.
In the United Kingdom Polystichum munitum has gained the Royal Horticultural Society’s Award of Garden Merit.
II. How to Grow and Care
Sunlight
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.
Climate and Temperature
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.
Watering
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
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.
Fertilizing
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.
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
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
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
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.
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
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
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
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.
Maintenance
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.
III. Uses and Benefits
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!
Find Where to Buy the Best Western Sword Fern (Polystichum munitum)
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