Scotch moss is not true moss, but is instead a herbaceous evergreen perennial that blankets the ground with hardy, dense mats of 1- to 2-inch tall plants that each spread 8 to 10 inches wide. Scotch moss blooms with clusters of tiny white flowers in late spring. Normally planted in spring from nursery starts or from seeds direct-sown in the garden, Scotch moss has a moderately slow growth rate, and it will take several years to blanket an area unless you plant them quite close together at the start. It is a relatively short-lived perennial that dies out after a few years. However, Scotch moss readily self-seeds, so there's generally no problem keeping an area carpeted with the signature yellow-green color.
|Common Name||Scotch moss, Scottish moss, moss sandwort|
|Botanical Name||Arenaria verna|
|Plant Type||Herbaceous, evergreen, perennial|
|Mature Size||1–2 in. tall, 8–10 in. wide|
|Sun Exposure||Full, partial|
|Soil Type||Rich, well-drained|
|Soil pH||Acidic to neutral (5.6 to 7.5)|
|Bloom Time||Late spring to early summer|
|Hardiness Zones||4–8 (USDA)|
Scotch Moss Care
The plant prefers well-draining, consistently moist soil. Scotch moss grows densest when planted in full sun, as partial shade can make them leggy and a little sparse. In warmer southern climates, though, they will perform best if they have some shade during the hottest part of the day. Plant them relatively close together if the goal is to blanket an area with greenery.
If this plant is grown in an ideal setting it's likely to do well without much maintenance, other than controlling the moisture level. But you should expect to remove and replace aging plants as they begin to falter after a few years.
Full shade is a recipe for disaster when it comes to Scotch moss. Providing it isn't going to suffer intense afternoon heat, it does best in sun. It can also tolerate partial shade, but too much can result in the plant becoming a less compact ground cover with an unattractive, undulating appearance.
In the warm end of its hardiness range, Scotch moss will need some protection from the peak afternoon sun to avoid burning out.
Scotch moss prefers a fertile, moist soil, but one that is also very well-draining. This is best achieved by making sure the planting area has plenty of organic material blended into it. Well-drained soil is an absolute must for this plant as it won't tolerate standing water.
You need to be careful not to over or under water Scotch moss. Either extreme can cause brown patches for this species.
Scotch moss intensely dislikes drought, and the soil should be kept consistently moist without allowing it to become water-logged.
Temperature and Humidity
Scotch moss is native to Western and Eastern Europe, and it thrives in mild, temperate climates. It may struggle with the intense heat of the afternoons of the South. Although it likes the sun, overly hot conditions can result in the plant burning and turning an unattractive brown rather than the usual golden-green shade.
In very fertile soils, Scotch moss won't likely need any feeding. For less rich soils, an annual feeding in the spring can be beneficial.
Just make sure not to overfeed or use a strong fertilizer. If the plant receives too much nitrogen, it can encourage excessive growth, and this can lead to mounds forming rather than the desired flat carpet-like appearance.
Types of Scotch Moss
The pure species plant (Arenaria verna) is almost never grown as a landscape plant, and is sometimes regarded as a weed in its native European range. A single cultivar, Arenaria verna 'Aurea', is the only type sold commercially.
No regular pruning or deadheading is necessary with this plant, though you may want to pluck out volunteer seedlings if you need to limit the spread of the plant.
As plants get old and die out after a few years, remove them and replace with fresh plants.
Propagating Scotch Moss
Scotch moss can be propagated in a number of ways, but the easiest is to simply cut patches or strips from an established area and replant wherever you want. Periodically lifting and dividing mats is also a way to rejuvenate an area where older plants have begun to die out. Here's how to do it:
- In late spring after active new growth has begun, use a sharp knife to cut out strips or sections of established plants, making sure there are roots attached to each section.
- Thoroughly loosen the soil in the intended new planting site, using a hand cultivator.
- Press the removed section into the new garden and press down firmly. If your goal is to quickly blanket an area, cover the area with plants spaced close together.
- Water thoroughly upon planting, then every few days until the new plant is well established.
Another propagation method is to carefully dig up and transplant the tiny volunteer seedlings that appear from the ample self-seeding that occurs with Scotch moss.
How to Grow Scotch Moss From Seed
Scotch moss is an easy plant to grow from seed—both when direct-seeded into the garden or started indoors several weeks before the last frost date of winter or spring. Plant the seeds by just barely pressing them into the soil or seed-starter mix. Provided the seeds get plenty of warmth and direct sun, and kept moist, they will germinate easily.
No winter protection is required for these plants. Make sure they are well-watered going into winter but avoid standing water over the winter months.
Common Pests and Plant Diseases
Scotch moss is a robust plant that isn't prone to any major diseases. Slugs do enjoy this ground cover, though, and you should keep a watchful eye out to prevent them from becoming a problem.
Crown rot is the only real disease problem with Scotch moss, and it generally becomes a problem only where the soil is too wet for too long. If your plants begin to turn yellow, it often means that crown rot is starting. Withholding water until the soil dries out fully will sometimes halt the rot. But if the rot continues, remove the entire plant.
Common Problems With Scotch Moss
There aren't too many problems with Scotch moss, but those that do occur will be experienced sooner or later by most growers:
Individual Plants Turn Brown
When the goal is a lovely flat mat of chartreuse greenery, it's annoying when patches of brown appear to disrupt the look. This symptom has several possible causes:
- Improper watering (too much or too little) can cause plants to develop rot or to die.
- It's possible that individual plants are simply old and need to be replaced. These are relatively short-lived perennials that usually begin to decline after a few years. A good rejuvenation session every few years will keep your patch looking its best.
Plants Form Mounds, Not a Flat Carpet
When your patch of Scotch moss begins to exhibit a mounded growth habit that disrupts the flat carpet look, the most likely culprit is too much fertilizer, which causes individual plants to grow higher crowns and sparse, leggy stems. Withholding fertilizer will usually control this problem.
How do I use Scotch moss in the landscape?
Unlike true mosses, Arenaria verna won't grow in full-shade or wet conditions. Instead, it makes a good choice for growing in rock gardens, in between flagstones, and along path edges in gardens that receive a decent amount of sun. It can also work as a lawn substitute in limited space, providing the foot traffic isn't too heavy.
Is there a similar plant that stands up better to foot traffic?
If Scotch moss suffers because there is too much foot traffic, try creeping thyme (Thymus serpyllum), which is a considerably tougher alternative.
What are the differences between Scotch moss and Irish moss?
Scotch moss (Arenaria verna) is often confused with Irish moss (Sagina subulata). When the plants are not flowering, the only real apparent visual difference between these species is the color of the foliage: chartreuse yellow-green for Scotch moss, medium to dark green for Irish moss. But when flowering, Scotch moss produces clusters of flowers, while Irish moss blooms with individual flowers. And Irish moss is a bit more tolerant of warm weather, performing better than Scotch moss in zone 8.
Irish and Scotch Moss, Sagina Subulate and Arenaria Verna. University of Wisconsin-Madison Division of Extension.