How to Plant, Grow, and Care for Irish Moss

Lovely Irish moss makes for a beautiful border between cobblestones or a lush lawn replacement. Gardening expert Sarah Jay shares tips for growing this ground cover.

A patch of thriving Irish moss with bright green blades and small, cute flowers with white petals covering an area

Contents

If you’re looking for a ground cover that produces tiny star-shaped flowers, look no further than Irish moss. It’s a great addition to a shady rock garden, the spaces between stepping stones, and next to water features. Irish moss (Sagina hawaiensis) can even be a lawn substitute in some areas. 

Its creeping stems tolerate light foot traffic. As it grows it creates a dense mat that is not only pleasing to the eye but soft on feet. It’s relatively disease-free, too. Growing Irish moss and its related cultivar (golden Scotch moss or Sagina hawaiensis ‘Aurea’) can add so much dimension to a garden.

One important thing to note is this plant is classed as an invasive species in areas of North America. In these areas, it can cause great damage to waterways. Please opt for something similar that is not invasive instead if you live in one of these regions.

So what do you need to grow a fine-textured carpet of Irish moss or Scotch moss? And what’s the difference between the two? Where do these plants even come from? Read on, and we’ll tackle all those questions here.

Overview

A vividly green Sagina hawaiensis plant with dainty looking flowers growing on gray rocks in a sunny area
Plant Type Perennial ground cover
Family Caryophyllaceae
Genus Sagina
Species Sagina hawaiensis (AKA Sagina subulata)
Native Area Europe and Scandinavia
Exposure Partial shade to full sun
Height 1-2”
Watering Requirements Regular
Pests & Diseases Slugs, moles, crown rot
Maintenance Low
Soil Type Well-draining, fertile
Hardiness Zone 4-8

What is Irish Moss?

Irish moss (Sagina hawaiensis) is commonly referred to as heath pearlwort and awl-leaf pearlwort. It is also known as Sagina subulata.

Scottish moss is technically not the same plant, but it’s a species often grown similarly in gardens. There is a specific cultivar of Irish moss (‘Aurea’) that also shares the common name.

Native Area

Many white and dainty flowers covering an area like grass with blooms extending into crevices of gray path with rock-like surface
It grows well on sandy soil with good drainage.

Both plants are native to Europe and Scandinavia. You’ll find these moss plants growing on banks and slopes near the fertile coast of the British Isles. But they’re also found anywhere between there and Romania in sandy well-drained soils.

Characteristics

A patch of deep green colored Sagina subulata blooming pure white flowers covering an area with dark brown plant material underneath
It thrives on rock gardens, making it ideal for landscaping.

A perennial, Irish moss grows only one to two inches tall and spreads about one foot wide. It and the Scotch moss cultivar are often grown in rock gardens, between stepping stones, or as a lawn substitute. Both are members of the carnation family and readily self-sow, creating a lovely mat of soft, green grass-like moss. 

The plant is known as awl-leaf pearlwort because its green leaves are shaped like an awl, a tool used for poking holes in leather or fabric. However, the dense, small clusters of awl-shaped leaves are soft, and the creeping stems don’t reach out to poke anyone. Small, white, star-shaped flowers with five petals bloom in spring at first and then sporadically throughout the growing season.

After each of the white flowers blooms and dies, small brown oblong capsules form, and triangular seeds are produced. These drop from the low-growing plant at a moderate rate, self-sowing as they go. This is how the thin stalks manage to spread out and self-propagate.

One of the main differences between Irish moss (Sagina hawaiensis) and Scotch moss (Sagina hawaiensis ‘Aurea’) is leaf color. Whereas Irish moss has rich green foliage, Scotch moss has gold to chartreuse leaves. Both have white flowers, and both grow similarly. So if you’re looking to fill space in between garden pavers, let color be your guide. 

Planting

A blooming patch of lawn substitute appearing vibrant green in color with countless white, dainty flowers
Use it to fill gaps on your lawn or grow in containers.

Plant Irish moss in spring after the danger of frost has passed. Choose a space in partial shade to full sun with fertile, well-drained soil. This could be on your lawn, in your garden, and even in a walkway where foot traffic is expected. Select a space where you’d like to fill in a gap with low-growing, green foliage, and white flowers.

If you live in an area with drought conditions or extreme heat, plant Irish moss in a container and place that container intentionally in your garden. Make sure the container has rich and well-drained soil that this moss likes. The same timing applies to containers too. Wait until spring when the last frost has passed.

To plant this moss (Irish and Scotch varieties), rake about an inch into the soil surface. Then take plugs with adequate roots, and place them on the ground or in your planter. Lightly press the plugs into the soil.

You should have no issue getting these plants started from seed too. Either start them indoors in winter a few weeks before the last frost or direct-sow them in spring outdoors. Give them a generous amount of sunlight or grow light. In two to three weeks, they’ll sprout. 

How to Grow

Once established, Irish or Scotch moss takes off and does well all by itself. Let’s discuss some of the conditions required for growing ground cover of this kind. 

Light

Abundant sunlight hitting an area covered with countless flowers of heath pearlwort, appearing vividly green with pure white flowers
It flourishes under the sun but requires some shade in warmer climates.

Irish moss prefers full sun to partial shade. In areas where heat gets high, partial shade or shade in the afternoon is a must. Grow Irish moss in an area that gets at least six hours of partial shade, and no more than one hour of scorching sunlight per day.

Water

A person waters sunlit plants using a hose for nourishment and hydration.
They love water, especially before the soil gets warm under the sun.

Always water your Irish moss in the morning, before the sun has warmed the ground. Keep the ground around your plant sufficiently moist, but not waterlogged. Especially when it has just been transplanted, it will need a consistent amount of water to root effectively. But light watering with a soaker hose is best for this sensitive ground cover. Insufficient or excessive water causes brown patches.

Plants like these prefer rich, moist soil near the coast. That’s one indication that Irish moss is not a drought-tolerant plant. If the season has been particularly rainy, do not water your moss plant. Again, excessive water on this low-growing plant will create brown patches rather than the lovely green-colored foliage you’d like in your lawn or garden. 

Soil

A hand tightly grips a gardening fork; its prongs buried in the dark, rich soil.
Use fertile soil with good drainage.

Grow Irish moss in soil that is rich, fertile, and well-draining. Think about its native habitat. Native moss plants like to grow on lush coastal hillsides in sandy soil. Underneath the sand, the coast is filled with rich humus soil. So choose an area that is similar to this, or create one in your garden, lawn, or containers.

Prepare a mix of compost, rich garden soil, and sand to fill in the area or containers you’ve chosen. Many guides suggest the plant can adapt to poor soils, at least after it’s established. The ideal pH range for Irish moss is 5.6 to 7.5.  

Temperature

A close up shot of dainty looking heath pearlwort flowers with pure white petals, surrounded by deep green leaves and stems
Each variety has a distinct temperature preference.

Ideal Irish moss growing zones include 4 through 8. Scotch moss prefers zones 4 through 7, as zone 8 is too hot for this delicate ground cover.

If you live outside this range, grow Irish moss in a container and bring it in when temperatures dip below 30°F (-1°C), and above 80°F (27°C). Either extreme produces brown patches in Irish moss that can bounce back in fall, restoring it to its lovely green color. Ideally, Irish moss prefers temperatures right around 60°F (16°C).

Because it is low to the ground, using frost or shade cloth may not be as effective as it would be for other plants. This is why ground cover plants need to be selectively placed and situated from the start. 

Fertilizing

NPK fertilizer. Close-up of a garden trowel filled with NPK fertilizer next to a watermelon plant. Fertilizers are granular and have blue ball-shaped granules.
NPK fertilizer helps keep these plants healthy through the seasons.

Irish moss likes a slow-release fertilizer applied once in the spring, annually. But fertilize sparingly, because high nitrogen levels can alter the spread and growth of Irish moss. Instead of growing in a compact and low-lying fashion, with too much nitrogen, it will grow in a mound. If you’re trying to cultivate a garden or lawn with a low ground cover, too much nitrogen is something you want to avoid.

Use a full-spectrum NPK fertilizer, or opt for something slightly lower in nitrogen. This provides adequate nutrition to foliage and flowers without overpowering green growth. 

Maintenance

There isn’t much pruning to do with ground cover plants like Irish moss. However, if there are yellowing or brown leaves, remove them as needed. 

Propagation

A patch of vibrant green heath pearlwort with countless blooming flowers and dry bits of old blooms scattered all over
It takes little effort to propagate this plant because it sows itself.

Propagating Irish moss is easy because it’s a self-sowing plant. Give it a good start in the garden and let it do its thing. Seeds tend to pop out of pods from flowers and help moss plants spread as they would in the wild.

Sow Seed

You can collect seeds and sprout seeds indoors in winter before the last frost. Plant the seeds on the soil surface in a rich starting mix that has a good amount of soilless content included. You can also plant seeds directly in the garden ground or on your lawn. Space the seeds at least eight inches apart. 

Division

Divided chunks of heath pearlwort with vivid green color and white flowers, placed in separate containers, with roots appearing light brown
It is easy to divide healthy chunks and plant them as long as they have healthy roots.

Another way to propagate these plants (outside of seeds) is to divide them from a healthy section of green growth in spring or fall.

Simply remove a section of the moss from your garden and pull it apart so that each resulting section has healthy roots. Then place them in partial sun to full sun spots of your garden. Provide adequate moisture to the plants and seeds, and you’ll have more Irish moss plants in your garden, and flowers that bloom in spring. 

Common Problems

When gardening with Irish moss, don’t fret too much if problems arise. Here are a few things to consider.

Growing Problems

A patch of light and vivid green Sagina subulata with green buds and underdeveloped flowers that have not bloomed yet
Too much nitrogen impacts growth and development.

As mentioned in the fertilizer section, don’t give Irish moss too much nitrogen. This makes it grow into a mound. High nitrogen could prevent flowering too, which means no seed for self-sowing. Instead, use a full spectrum, balanced, slow-release fertilizer sparingly. 

Remember not to water too much, as this can create brown patches when gardening with Irish moss. The same goes for too little water. If brown patches emerge, no problem. Remove them and let the rest of the patch continue to grow with the correct amount of water.

Too much sun causes browning in Irish moss patches too. So if you’re not sure whether or not the space you’ve chosen is too sunny, plant the moss in a container first and move it around as needed, then plant it in the ground once you’re sure of its placement. 

Pests

Close-up of a large slug on green grass which features a slimy, elongated body with a mottled brown coloration.
They are prone to slug infestations.

The only pest Irish moss has to contend with inside the garden is the infamous slug. The easiest way to deal with them in the garden is to give them an intoxicating beer trap. They can’t resist the beer and will perish as they drink.

If slugs get out of hand and infest your Irish moss, try an organic slug bait. You should only have to apply this once per season. 

Diseases

A vibrant green patch of lawn with scattered white flowers blooming from heath pearlwort with plant debris in the vicinity
It is vulnerable to specific diseases caused by too much moisture, such as crown rot.

Crown rot is the only disease that affects Irish moss. This usually occurs when there is too much water present in the soil, and it’s caused by the same fungal pathogens that cause root rot.

Prevention is the best method for controlling crown rot, as it can cause the death of the entire organism. If you notice yellowing leaves in areas where moisture is high, remove them and let the plant dry out. Then apply small amounts of water only after the soil has dried. If this doesn’t improve conditions, remove the entire plant to prevent the spread of fungus to the rest of your garden. 

Frequently Asked Questions

Where does Irish moss grow best?

Irish moss prefers rock gardens, spaces between pavers, or anywhere in your garden ground cover is preferred.

Does Irish moss spread fast?

Even though it self-propagates by seed, it’s not a vigorous spreader, and it’s easy to remove. There’s no need to worry about planting an aggressive moss.

Does Irish moss come back every year?

In hotter areas, it may get a little scorched in summer and die back in winter. But this perennial will return in temperate seasons.

Can you walk on Irish moss?

Absolutely. Even though the leaf shape is compared to the pokey awl, it’s soft on feet. That’s why it’s often chosen as a ground cover.

Share This Post
Vibrant purple Creeping Thyme flowers bloom in clusters, forming a mesmerizing carpet. The tiny blossoms showcase delicate petals, adding a burst of color. The lush green leaves of Creeping Thyme create a dense and textured ground cover resembling a vibrant lawn.

Ground Cover

How to Plant, Grow, and Care for Creeping Thyme

If you’re looking for a low-maintenance groundcover that will cut down on mowing and smells great, creeping thyme is perfect. In this article, gardening expert Melissa Strauss will tell you how to replace your lawn with an aromatic herb that pollinators love, too!

Ground cover thyme plant growing instead of grass in lawn

Ground Cover

11 Ground Cover Plants That Can Replace Your Grass

Are you looking for a ground cover to add to your garden instead of grass? There are a number of different ground cover plants that can substitute for grass, depending on your climate. In this article, gardening expert Madison Mouldon shares her favorite ground covers that can replace grass, help pollinators, and look fantastic in your garden.

cold hardy ground cover

Ground Cover

15 Cold Hardy Ground Cover Plants For Cool Weather

Looking for a cold hardy ground cover plant to dress up your garden in cooler weather? There are plenty of different options to choose from, even in colder hardiness zones. In this article, certified master gardener Laura Elsner looks at her favorite cold hardy ground cover plants, with names and pictures of each!