Korean Rock Fern (Polystichum Tsus-simense) Care + Growth

The Korean Rock Fern is a lovely compact fern that’s bursting with character.

With its fine-toothed leaves and lance-shaped fronds, it’s got just enough “rough around the edges” to keep you coming back for more.

I’m not sure if K-Ferns are a trend yet, but I’m down…

Named the “Rock Fern” for its remarkable ability to grow in rocky crevices, you can be sure this hardy plant will thrive in comfortable home conditions.

Ours certainly did. We’ve grown Polystichum Tsus-simense as both a houseplant and a terrarium plant with great success.

Read on to learn how to care for this little bushy number and keep it looking healthy and happy.

Temperature/Humidity

Unlike many typical terrarium and household ferns, the Korean Rock Fern isn’t tropical – it’s temperate.

I know. Gasp.

But trust me, it comes with its benefits. 

Native to East Asia (though not necessarily Korea), this temperate species is incredibly hardy. To the point where if you’re growing it indoors, you needn’t worry about it suffering from the cold.

Anything over 60°F will be more than enough on the temperature front.

It appreciates higher humidity, so it’ll do nicely in a tropical terrarium with more fern friends. But it’s not sensitive to it like a Maidenhair Fern is.

Watering

Polystichum Tsus-simense has more epiphytic watering tendencies than most ferns. 

Growing in rock walls, it’s accustomed to not always having access to an abundant water source. The classic soak-and-dry cycle is more common in the wild. 

That said, it still appreciates consistent, even moisture.

This plant is also a bit more sensitive to soggy conditions, so you want moist soil, not waterlogged soil. Take care not to overwater, and choose an appropriate substrate with plenty of drainage. 

Lighting

Being an epiphyte and not a native forest floor dweller, the Korean Rock Fern is used to receiving more sunlight than your standard tropical species. 

So it can handle a more direct sun, though I wouldn’t actually put it somewhere where it would receive a lot of it. 

The deep green fronds suggest it’s well-adapted to the shade (more color = more chlorophyll), and the standard “bright indirect light” works well for this plant in the home, too.

Substrate/Soil

You can plant the Korean Rock Fern terrestrially in your chosen soil or mount it epiphytically. 

If you go with the soil option (as we have), I’d recommend a light and airy tropical mix. Something that lets the roots breathe and drains well.

Any variation of the classic ABG mix is an excellent starting point.

We’ve used a coco-coir-based terrarium substrate blend supplemented with pumice and orchid bark for extra aeration. Plus, a little earthworm castings for some slow-release fertilizer goodness.

If you’re mounting your fern (e.g., on cork bark), I’d recommend wrapping the roots in sphagnum moss to give them a moisture-retentive boost.

Growth

Despite its long, lance-shaped leaves, this evergreen fern grows in a surprisingly compact pattern.

The fronds gently twist and weave amongst each other, making the toothed edges look like they are almost interlocking. It’s really beautiful. 

Polystichum Tsus-simense is a pretty slow grower, too. So it’ll take a good while before it maxes out at around 20 inches tall – making it perfect for terrariums.

Even then, it’s easy enough to trim back.

Propagation

Propagating this fern is super simple; it’s just simple division.

Start by removing your mature plant from its pot and exposing the root ball. From there, use your hands to separate the fronds at the base, creating a loose “separation.”

You’ll want all the soon-to-be independent plant sections to have a healthy amount of roots and leaves.

Then, just go ahead and divide it.

You can use a sharp pair of scissors to do this, but sometimes (as in this case), the roots are fine enough to gently tear them apart. 

There you go, you have two new plants! 

Provided you have healthy plant sections, they’ll be fine to plant up as they are. We popped our mother plant back in the pot, and the new plant division went straight into a terrarium.

Varieties and Similar Plants

Polystichum is the genus of “Shield Ferns.”

Most of them are pretty large and better suited to gardens than homes or terrariums. It’s really only the Korean Rock Fern that sees a lot of use.

That said, the Polystichum ‘Spiny Holly’ looks like another compact beauty.

And there is a larger version of the Korean Rock Fern going by “Polystichum Tsus-simense var. Mayebarae” should you want to fill a larger terrarium or space.

Finally, if you want a fern with a similar vibe, I’d recommend taking a look at the Autumn Fern (Dryopteris erythrosora). It has a sharp-toothed edge to its fronds and lovely warm hues.

Or how about the Rabbit’s Foot Fern?

References

• https://bsapubs.onlinelibrary.wiley.com/doi/full/10.3732/ajb.94.8.1413