Irish moss is a plant typically used for landscape gardens. It is native to western and central Europe.
They’re cold-hardy in Zones 4 to 8, though with enough care, they can survive beyond those zones.
Consider Irish moss if you’d like to cover bare rocks or at the edges of pathways.
This article will briefly cover the basics of growing them, from seeds to propagation. Keep reading to discover how to cover your garden with a green carpet.
What Is Irish Moss?
Irish moss (Sagina subulata) is a low-maintenance, low-growing evergreen perennial from the carnation family that only resembles moss. Because of that, it has very different needs from actual moss.
This green fuzzy cover grows all over the British Isles, including Ireland, as its name suggests.
These plants are hardy but slow-growing. In fact, they can take months to fill out a garden.
However, they’re perfect ground cover for rock gardens. It’s also soft, so it’s ideal for garden paths. You can typically find Sagina subulata between pavers, beside pathways, stepping stones, and even as a limited-area lawn substitute.
They don’t like full shade or very wet conditions and prefer sunny or partially shady areas.
If you give these plants the right conditions, they can add a dense spread of green to your garden.
How Can I Grow Irish Moss from Seed?
It’s a good idea to lightly press Sagina subulata seeds in seed flats indoors about a month before your last average frost date. Don’t cover them since they need light to germinate.
You can expect to see some sprouts after two to three weeks. They’ll establish shortly after that as well.
Ensure the flat soil is always moist and between 55 and 60 degrees Fahrenheit. Harden off the seedlings before transplanting them outside, ideally after the late spring frost.
You can sow Irish moss seeds directly into the ground in spring. However, you’ll need to watch out for birds that may eat them and cause your lawn to decline in greenness.
How Should I Care for Irish Moss?
Irish moss can tolerate light foot traffic and urban pollution well, making it a popular landscaping solution in the correct zone. It can even survive in rock gardens or lawns that can’t grow grass well.
To care for Irish moss, check the following factors to ensure that it thrives in an ideal environment:
Light
Grow Irish moss in full sun or partial shade. However, Sagina subulata doesn’t like intense heat, so if you live in a zone with high heat, it’s better to put it where it gets covered by afternoon shade.
On the other hand, too much shade can make it grow tall and leggy, making it less compact and unattractive.
Soil
Irish moss can be planted in sandy, loamy, and chalky soils as long as they’re nutrient-rich. The sand must be of good quality, rich, and fertile.
Consider adding organic matter if you live in an area with hot and dry summers or if your soil could be more fertile.
Ensure you don’t place Sagina subulata where water is sitting or retained.
Water
Generally, the soil should be consistently moist but not soggy. If you have a soaker hose, set it to a mild rainfall setting.
This plant isn’t drought-tolerant, so keep it green by watering it consistently every few days (or more, depending on the heat). It’s a good idea to water in the morning.
Temperature
Irish moss is ideal for USDA Zones 4 to 8. Outside those zones, the plant will struggle in hot and dry summers.
If you live outside those zones but still want to grow Irish moss, we recommend planting them in a container that you can move in the shade if needed.
Fertilizer
A slow-release fertilizer every spring can help your Irish moss grow well. A 5-5-5 NPK fertilizer or a slightly lower nitrogen formula are good options.
That’s because overfertilization from too much nitrogen can cause them to have an irregular growth pattern or form mounds, which won’t result in a compact, low-growing plant.
If your Sagina subulata is growing slowly, consider adding calcium to speed it up.
Pruning
Pruning isn’t necessary. However, trimming your Sagina subulata using clean scissors or shears from steps, pathways, and other structures is ideal for keeping them neat.
Pests
Irish moss is mostly pest- and disease-free, so you won’t have to worry about worms. However, it can be prone to slugs.
Fortunately, you can solve the problem by applying organic slug bait every year. Sometimes, you might have to deal with moles that pass beneath the plants, lifting them as they go. You can simply pat the green moss back down to the soil.
Overwintering
Irish moss can survive the winter without protection in USDA Zone 4. You’ll notice the plant turning brown during the winter, but rest assured that it will naturally revive and turn green in spring when the rains and warmer temperatures hit.
Potted Irish moss can also survive outdoors during the winter. However, the containers will need protection from the cold to prevent damage.
You can protect your Irish moss by:
- Putting a silo around the container
- Adding mulch on top
- Putting a protective wrap over it
How to Propagate Irish Moss
Propagating Irish moss lets you thin out and revive browned, unsightly, or unflourished patches. Follow the steps below to propagate Irish moss:
- Lift the whole clump using a shovel. Separate the clumps into smaller sections using a shovel or pruner. Ensure that each section has decent roots.
- Replant the clumps in new places, planting them to the same depth as their original place.
- Trim any wayward stems after you plant the Irish moss. Water well and keep the plants moist until there’s new growth.
TIP: Divide the Irish moss in early spring so it has the whole season to establish itself in the soil and green once more.
Potting and Repotting
Irish moss is mainly used as handy green ground cover, but it’s also good to grow in containers — particularly ones that are wide and shallow to accentuate the natural spread.
Fill them with potting mix and ensure the plants are always well-watered.
Using a clay or terracotta pot is ideal since the material will naturally wick away excess moisture from the soil, helping the plant not get too waterlogged.
If you plant Irish moss in pots, you’ll need to repot them when they outgrow the container (which can generally take three years, depending on the pot’s size).
Frequently Asked Questions
You can have a green and healthy path of Irish moss with regular water and the right sun.
Irish moss can be confused with other plants, and it’s not always the best option for creating a lush outdoor carpet.
Below, we’ll clear up some confusion so you can better understand this plant.
What’s the Difference Between Scotch Moss and Irish?
Irish moss (Sagina subulata) and Scotch moss (Arenaria verna) are both prostrate herbaceous evergreen perennials in the carnation family. They grow well in full sun and partial shade, make good ground cover, and have little white flowers when in bloom.
However, these two have several differences:
- Irish moss has emerald green leaves, while Scotch moss has a more golden shade.
- Scotch moss grows slightly taller at 2 inches than Irish moss, which grows at about 1 inch.
- Irish moss spreads across the ground farther.
- Scotch moss is less common as well.
Can it Withstand Foot Traffic?
Yes, a carpet of Irish moss can withstand light foot traffic. However, ensure the plants are well-established in your garden before stepping on them.
If you want a plant that can withstand heavy foot traffic, creeping thyme (Thymus serpyllum) is a great choice.
Is It Okay to Grow Indoors?
Yes, you can grow Irish moss in containers, but you’ll have to re-pot it when it outgrows its current container.
However, they’re known more for landscaping. You can start growing it indoors and eventually replant it once it’s better established for some more extra green cover.
Is Irish Moss Seaweed Different?
Yes, Irish moss and Irish moss seaweed are different.
Irish moss (Sagina subulata) is used to landscape a garden. Meanwhile, the seaweed (Chondrus crispus) is a red seaweed that’s usually deep red or dark purple in color.
Chondrus crispus, also known as carrageenan moss, is a variety of sea moss that can be found growing on rocks around the shores of Ireland and some coasts along Europe, such as Iceland and the Faroe Islands.
This perennial seaweed can be used in dairy and processed foods.
Conclusion
Irish moss is an herbaceous perennial plant native to some parts of Europe that thrives best in USDA Zones 4 to 8. It makes for great ground cover and blooms little white flowers in the spring and summer.
Ensure they get the right amount of water since too much or too little can cause brown patches. Check that they’re planted in nutrient-packed soil and get just the right amount of sun. Thin them out or revive brown patches by propagating them.
Irish moss takes some effort and a lot of patience to grow. However, if you put in the effort, you’ll have a beautiful green carpet to reward you.
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