Native Plants 101: Western Sword Fern

Sword ferns (Polystichum munitum) are the workhorses of the native plant garden. Like many creatures and plants that are common and abundant, we often forget to appreciate the subtle beauty and utility of these large, helpful, ecologically important, and undemanding ferns.

In suburban, rural, and wildland area of Puget Sound, these ferns are extremely important habitat features that facilitate and protect migrating frogs as they move from breeding ponds to upland areas. Note that when managed properly, suburbs and urban creeks and uplands can be productive habitat for frogs despite the presence of development, as this article from the AP so eloquently explains.  Of course all sorts of other creatures, charismatic or not, benefit from their enclosing fronds.

One reason we enjoy a hike in the woods is the green backdrop – strive to recreate a natural setting for western sword fern (lower left, lower right) and you will be rewarded!

Sword fern roots are famous for holding slopes. Having grown them in pots, from spores, I can attest to the cement-like quality of their massive root balls. They also take any amount of abuse – you can dig them up and replant almost at will, with less supplemental watering than you might think.

Despite their many valuable characteristics, sword ferns risk being overlooked as too common to be interesting. I may be guilty of this attitude from time to time, but only in situations where they are misused, overused, or not sited and cared for properly.  More on this below.

Using sword ferns in the garden and landscape:

These beefy ferns have a wide tolerance for sun/shade and dry to wet conditions. They are not picky as to soil type – our low nutrient, acidic, gravelly, or clayey glacial soils are where they evolved. They naturally grow in difficult conditions of dry shade under conifers, but appreciate lots of leaf litter, and will respond to organic matter and compost amendment with lush growth.

The most pleasing arrangement for sword ferns is to echo or recreate their natural setting in conifer forests. Tucking them next to a large rock or a stump or rotten log, with a backdrop of conifers and a variety of woodland shrubs will make them look at home. They can also provide a great lower-story in your hedgerow.

Sword ferns in a natural setting
Sword ferns in a natural setting
Sword ferns in a steep ravine - a familiar northwest sight
Sword ferns in a steep ravine – a familiar northwest sight

Sword ferns are evergreen, which makes them valuable on the aforementioned slopes, but also help with covering bare spots during the winter. Although they look a bit tattered by the end of winter, it is worth it to have them protecting the soil and creatures. If you like to be tidy you can cut the old fronds back in later winter or early spring to highlight the new ones emerging.

New fronds in crown getting ready to expand
New fronds in center getting ready to expand-don’t cover the crowns with soil or leaves when planting
Contrasting leaf textures enhance the enjoyment of all plants in the mix

The reason they are popping up in public and commercial landscapes is, I think, partly due to the desire for natives as a lower maintenance, more nature-friendly feature. Since sword ferns are tough and evergreen, (and available) it’s tempting to use them – a lot. But when large areas are carpeted with repeating regimented rows of uninterrupted, dark, rather coarse, sword ferns fronds, the effect is monotonous. They really need some contrast with leaves of a different color and texture, and plants at different heights around them to look their best. Even in nature, where a whole hillside may be covered with them, there are spaces between them with leaf litter, small herbaceous plants, woody shrubs, and the ever-present cedars, and Douglas firs to provide context.

They also risk becoming bleached or tattered if placed in an overly sunny spot. Winter takes a toll on their appearance, and it’s important to either cut them back at the appropriate time (early spring), or mix them in as supporting players for other plants to camouflage the blemishes, rather than shove them forward to carry the whole show on their own. If covering a lot of ground is the goal, use them in groups with companion plants, or at intervals to provide support and background for a unified whole. Don’t expect them to look their best in full sun all day, with a lot of reflected heat from concrete. Remember, too they are large when grown well, so allow for future space requirements and be mindful of scale.

Cultural requirements:

Part sun to full shade.

Well adapted to acidic, leached forest soils of the PNW, a nice layer of compost on the surface will improve overall health.

Tolerant of fairly wide range of soil moisture from wet to dry. Adapted to winter wet/summer dry conditions, as are all PNW natives. Will look fresher with occasional irrigation.

Evergreen  – good for covering the ground to intercept and filter winter rains, provides multi-season interest and protection for insects, birds and other creatures year-round.

Mostly pest and disease free.

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