How to Plant, Grow, and Care for Korean Rock Ferns

2023-02-04
How to Plant, Grow, and Care for Korean Rock Ferns

Korean rock ferns (Polystichum tsus-simense) are beautiful and easy-to-grow ferns that can be grown both indoors as a houseplant and outdoors as a garden plant in warmer climates (USDA Hardiness Zones 7-10). Native to eastern Asia, these ferns are often found growing on rock walls in locations from full sun to full shade. Their ability to grow in deep shade and where they regularly dry out, along with their persistent green fronds and dark stems, make Korean rock ferns an excellent choice for protected areas outdoors where few other plants will survive. Indoors, these ferns can grow in less light than other common houseplants.

Korean Rock Fern Overview

Genus Name Polystichum tsus-simense
Common Name Korean Rock Fern
Plant Type Houseplant, Perennial
Light Part Sun
Height null to 20 Inches
Width null to 18 Inches
Foliage Color Blue/Green
Zones 10, 7, 8, 9
Propagation Seed

Where to Plant Korean Rock Ferns

In general, Korean rock ferns perform best as an indoor plant but can be grown outdoors in warm, wet climate zones. Being small, clump-forming plants, they do not require frequent repotting and can be grown with similarly sized plants that have similar cultural requirements. Forced air vents, fans, and cold drafts should be avoided.

Outdoors, Korean rock ferns will do well in protected locations with bright, indirect light and regular moisture, but they can survive with some drying between waterings. Because of their fibrous root system, they do well in locations with shallow soils, but benefit from mulching for more consistent moisture. Avoid planting these ferns near aggressively spreading plants such as lilyturf (Liriope spp.) or English ivy (Hedera helix).

How and When to Plant Korean Rock Ferns

Outdoors, plant Korean rock ferns in spring to allow plants to become established throughout the growing season. Dig a hole twice the width of the root ball and set in the center of the hole. Sprinkle some granular fertilizer around the root ball and refill with soil. Water gently and maintain moisture throughout the first growing season.

Care Tips for Korean Rock Fern

Light

These ferns prefer bright indirect light, but can acclimate to full sun in cooler conditions. Korean rock ferns can also grow, but not thrive, in dimmer lighting where they will maintain their color, but show very little growth.

Soil and Water

Korean rock ferns prefer moist conditions, but will not tolerate standing water for long periods of time so make sure to plant it in well-drained soil. In a container, potting mix with added perlite will ensure ample moisture retention while maintaining proper drainage.

Temperature and Humidity

As with most ferns, these plants will do best when given warm temperatures and high humidity. Temperatures over 90°F or lower than 32°F will slow growth or kill plants. 

Maintain humidity around plants outdoors by applying an organic mulch around uncovered soil. Indoors, Korean rock ferns will do best in more humid locations around the house such as the kitchen and bathrooms.

Fertilizer

A balance fertilizer once a month, while plants are actively growing, will keep plants green and thriving. Outdoors, the addition of compost and mulch to the soil will help keep moisture locked in the soil while also supplying plants with nutrients.

Potting and Repotting

When grown indoors, Korean rock ferns can be repotted anytime during the year. Due to clumping growth, plants only require repotting when they have begun to outgrow their current pot. Excessive root growth from the bottom of the pot and bulging sides (in plastic pots) will indicate repotting is necessary.

Pests and Problems

Korean rock ferns experience few diseases aside from root rot and mealybugs. Root rot can be avoided by using a well-draining soil mix and never allowing plants to sit in standing water. Treat mealybugs with an organic pesticide such as neem oil. Individual mealybugs can be removed with your fingers if you aren't squeamish.

How to Propagate Korean Rock Fern

Like most ferns, Korean rock ferns grow from spores and require at least a year before true fronds are noticeable. But if you're patient, you can collect spores and grow them into new ferns.

  1. Fill a small plastic container about halfway with evenly moist potting mix.
  2. Hold fertile fronds over the container, spores facing down, and tap or flick the tops to allow spores to settle on the soil surface. Fern spores are brown and dust-like, making them hard to see once they’ve touched the soil. A white sheet of paper can also be used to collect spores before applying them to the soil.
  3. Cover the container and place it in a warm, bright location away from direct sunlight and cold drafts.
  4. After a week, check to make sure the soil is still moist and spritz with a water bottle if necessary. Repeat weekly to maintain moisture.
  5. Over time, green structures will begin to grow on the soil surface. These will become new fern plants in time. Continue spritzing with water until the first true fronds begin to appear. 
  6. Once at least three fronds have grown on plants, they can be gently removed and repotted.

Companion Plants for Korean Rock Fern

Outdoors, plant your Korean rock ferns with non-aggressive plants such as wild ginger (Asarum candense), smaller hostas (Hosta spp.), and lungwort (Pulmonaria spp.)

Ferns pair well with other moisture-loving houseplants such as peace lilies (Spathiphyllum spp.), pilea (Pilea spp.), and pothos (Pothos spp.).

Frequently Asked Questions

  • Can Korean rock ferns grow in a north-facing window?

    Unlike many other plants, Korean rock ferns will grow in a north-facing window. However, they will do better with brighter, indirect light.

  • Are Korean rock ferns safe around pets?

    Yes, these ferns are generally safe for cats and dogs, although if consumed, they may cause some stomach upset.

Related Article

How to Plant and Grow Rose of Jericho

How to Plant and Grow Rose of Jericho

Rose of Jericho is a unique houseplant that can survive with minimal water, making it a great option for travelers and forgetful gardeners.
21 Adorably Petite Plants for Fairy Gardens

21 Adorably Petite Plants for Fairy Gardens

Color is always nice, but scale is everything when choosing miniature garden plants. Peruse our favorite picks for fairy gardens and terrariums.
13 Colorful Nectar Plants for Pollinators

13 Colorful Nectar Plants for Pollinators

Create a gorgeous, pollinator-friendly garden by including these nectar-rich plants.
Is Coleus a Perennial or Annual? Here's How to Grow It Both Ways

Is Coleus a Perennial or Annual? Here's How to Grow It Both Ways

Is coleus a perennial that comes back every year? That depends on where you live and how you care for it. Use these tips to enjoy coleus as a colorful perennial or annual plant.
How to Plant and Grow Ranunculus

How to Plant and Grow Ranunculus

Ranunculus are favorite flowers for weddings, arrangements, and gardens. Here's how to plant and grow ranunculus.
How to Plant and Grow Glossy Abelia

How to Plant and Grow Glossy Abelia

This guide on how to grow glossy abelia includes essential planting and care tips such watering, fertilizing, and pruning needs. You'll also find popular types of abelia to grow and pretty companion plants for this flowering shrub.
Hydrangeas Not Blooming? 7 Reasons Why and How to Fix the Problem

Hydrangeas Not Blooming? 7 Reasons Why and How to Fix the Problem

Hydrangeas not blooming can be a frustrating problem for gardeners. These straightforward tips will promote tons of long-lasting flowers.
10 Best Sweet Potato Companion Plants for Larger Harvests

10 Best Sweet Potato Companion Plants for Larger Harvests

Mix and match these sweet potato companion plants in your vegetable beds for pest-free crops and easier gardening.
How to Harvest Mint, Dry Mint, and Store Mint

How to Harvest Mint, Dry Mint, and Store Mint

Learn how to harvest mint to keep plants more manageable and gather fresh mint leaves for cooking, drying, and storing!
How and When to Harvest Radishes at Their Peak

How and When to Harvest Radishes at Their Peak

These easy-to-follow tips will help you figure out how and when to harvest radishes for the best flavor and size. Plus, get troubleshooting advice if your radish roots aren't developing properly.
How and When to Start Tomato Seeds Indoors

How and When to Start Tomato Seeds Indoors

Find out exactly how and when to start tomato seeds indoors so they'll be ready to transplant into your garden in spring.
Tillers vs. Cultivators: How to Choose the Right One for Your Gardening Tasks

Tillers vs. Cultivators: How to Choose the Right One for Your Gardening Tasks

Learn the differences between tillers and cultivators and the tasks they're best suited for.
Here’s What Not to Put in Compost to Avoid a Contaminated Bin

Here’s What Not to Put in Compost to Avoid a Contaminated Bin

Composting is a simple way to turn your kitchen and yard waste into food for your garden. But some of these items should never be in compost.
Easy Lawn Repair for Patchy Grass Using Seed or Sod

Easy Lawn Repair for Patchy Grass Using Seed or Sod

With a bit of grass seed or sod, lawn repair is easy, and you’ll soon have a lush green carpet again.
What Are the Tiny White Bugs on Your Plants? 4 Common Pests They Could Be

What Are the Tiny White Bugs on Your Plants? 4 Common Pests They Could Be

Tiny white bugs on plants in your home or outdoors can be a big problem. Learn how to identify and get rid of them with this guide.
How to Spot 5 Common Plant Diseases and Keep Your Garden Healthy

How to Spot 5 Common Plant Diseases and Keep Your Garden Healthy

Protect your plants from the most common diseases. Learn to recognize the symptoms and how to prevent these diseases in the first place.
How to Landscape with Rocks and Stones in Your Yard

How to Landscape with Rocks and Stones in Your Yard

Decorative rocks and stones add another element of nature to your yard, whether you grow hydrangeas, tulips, or cacti.
Landscape Planning Tips From Start to Finish for a Perfect Yard

Landscape Planning Tips From Start to Finish for a Perfect Yard

Even if you're a beginner, these simple landscape planning tips will take the mystery out of designing your yard's ideal layout.
10 Native Alternatives to Invasive Plants Growing in Your Garden

10 Native Alternatives to Invasive Plants Growing in Your Garden

Use native plants in your garden instead of popular invasive landscape plants: See a list of common invasive plants, plus native alternatives to plant instead.
Your Seasonal Lawn-Care Schedule for the Midwest

Your Seasonal Lawn-Care Schedule for the Midwest

Use our lawn-care schedule to help you maintain a beautiful yard all year long. You'll learn exactly when to mow, aerate, fertilize, and overseed.