Korean rock fern
Polystichum tsus-simense · Dryopteridaceae
A small, neat evergreen fern with dark, finely cut fronds and blackish veins. It keeps a tidy shape without any care.
- Size
- 14 in tall, 14 in wide
- Zones
- 6 to 9
- Light
- Part shade to shade
- Flowers
- Grown for its leaves
- Pets
- No toxicity recorded
- Job in a bed
- Edging
A bed built around Korean rock fern
The planner designed this bed around Korean rock fern when this page was made: a 12 × 6 ft (3.7 × 1.8 m) English border in zone 6, part shade. It chose the other plants from the 513 that suit those conditions, and says below why Korean rock fern stands where it does.
The plants
- 1 Korean rock fern × 8, dark green leaves
- 2 Woodland strawberry × 8, white
- 3 Leadwort × 10, blue
- 4 Blue wood aster × 3, lavender
- 5 Japanese meadowsweet × 3, pink
- 6 Bleeding heart × 1, pink
- 7 Checkered lily × 5, purple
- 8 Yellow trout lily × 12, yellow
Why this plant
- The only plant grown for its leaves. Leaf lasts all season, where a flower lasts a few weeks.
- The only fine leaves here. The rest are medium and bold. A change of leaf keeps plants distinct when nothing is in flower.
Why here
- In the middle. At 14 in it is the step between leadwort (10 in) in front and bleeding heart (2½ ft) behind: each is seen over the one before.
- 8 plants in 2 groups (5 and 3). Seen again further along, the same plant ties the bed together.
- Fine leaf against bold. Japanese meadowsweet is beside it: the strongest contrast of leaf there is.
Why now
- Here for its leaves, all year. They cover the 12 weeks between early March and late November when nothing on the plan is in flower.
- The only leaves in winter. From November to March it is what there is to look at.
Planned as an English border: 4 of the 6 groups (67%) are drifts, longer along the bed than they are deep. The most in flower at one time is 3 kinds, from early May. The scheme leans cool (blue, lavender, pink and purple) and uses yellow for warmth, with white to calm things between them.
The planner's own design check: 13 Excellent, 4 Good. It flags one thing to watch: Nothing on this plan is highly poisonous or an aggressive spreader.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where Korean rock fern goes in a border
At 14 in it belongs at the front of a bed. In the planner's ten height classes it is short (12 to 18 in).
Its job: edging. A low, neat plant used in short runs of three or five along the front to finish the edge (or, in a formal bed, in one even row).
Small and well-behaved, so it suits the front of a bed and the company of miniature hostas.
- Edging shady paths
- Small gardens and containers
- Among rocks
What to plant with Korean rock fern
Plants recorded as good partners for it, and what each pairing does:
- Hosta 'Blue Mouse Ears': spires rising out of its mound; low enough (8 in) to stand in front of it; happy in the same moist soil.
- Black mondo grass: spires rising out of its mound; low enough (8 in) to stand in front of it.
- Strawberry begonia: adds the flowers, mid May to late June; low enough (8 in) to stand in front of it; happy in the same moist soil.
Questions about Korean rock fern
Does Korean rock fern need sun or shade?
Korean rock fern grows in part shade (2 to 4 hours of sun, mostly in the morning) and shade (less than 2 hours of direct sun, or bright dappled light). It is one of the few that also put up with deep shade.
It wants soil that stays evenly moist, rich in organic matter, and a good soak in dry spells.
What zones does Korean rock fern grow in?
USDA zones 6 to 9. It is hardy to zone 6, which means it survives winter nights down to about 0 °F (−18 °C).
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
How far apart should Korean rock fern be planted?
12 in (30 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 14 in (35 cm), so a group knits into one patch.
It grows 14 in (35 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many Korean rock fern plants do I need?
At 12 in apart, set out in staggered rows:
- 12 to fill 10 square feet (about 1 m²)
- 11 for a single row 10 ft (3 m) long
- 38 to fill a 4 × 8 ft bed on its own
In a mixed border, plant it as runs of three or five along the front (or one even row, in a formal bed).
In the bed above, the planner used eight in two groups.
Is Korean rock fern poisonous to dogs and cats?
No toxicity is recorded for dogs, cats, horses or people, according to NC State Extension.
"Not toxic" is not "edible": a pet that eats a lot of any plant can be sick.
Is there a native plant like Korean rock fern?
Korean rock fern comes from Zimbabwe to South Africa; Himalaya to Japan and Vietnam. These North American natives come closest to doing its job:
- Maidenhair spleenwort: the same job in a bed; 8 in shorter, 6 in narrower.
- Bulblet fern: a drift, not an edging, 4 in taller.
- Sedge 'Bunny Blue': the same job in a bed; 4 in shorter, medium leaves, not fine.
Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.
Do deer eat Korean rock fern?
Mostly not. NC State lists it as resistant to deer and rabbits. No plant is proof against a hungry deer in a hard winter, but this one is low on the menu.
What does Korean rock fern look like in winter?
Korean rock fern keeps its dark green leaves all winter, so it is one of the plants that hold a bed together from November to March, when the perennials have gone.
More Polystichum
- Braun's holly fern Polystichum braunii
- Christmas fern Polystichum acrostichoides
- Makino's holly fern Polystichum makinoi
- Soft shield fern Polystichum setiferum
- Tassel fern Polystichum polyblepharum
- Western sword fern Polystichum munitum
In these guides
Every fact on record
- Type
- Fern
- Size
- 14 in (35 cm) tall, 14 in (35 cm) wide
- Plant
- 12 in (30 cm) apart
- Height class
- Short (12 to 18 in)
- Place in the bed
- Front
- Flowers
- None: grown for its foliage
- Leaves
- Fine texture, evergreen; dark green
- Shape
- Mounding, clumping
- Hardy in
- USDA zones 6 to 9
- Light
- Part shade, shade
- Soil
- Rich, evenly moist
- Water
- Moderate
- Feeding
- Light, in spring
- Family
- Dryopteridaceae
- Comes from
- Zimbabwe to South Africa; Himalaya to Japan and Vietnam
- Stands up to
- Deer, rabbits, deep shade
Checked against NC State Extension. Flowering times are for zone 5: later in colder zones, earlier in warmer ones. Toxicity and spread information is a general gardening guide, not veterinary or medical advice, and invasive status varies by region. If a person or pet eats a plant, contact poison control or a vet. Check your local invasive species list before planting anything with a spread warning.