Scotch Moss (Arenaria verna) is often confused with its close relative - Irish Moss. Sometimes it's even referred to as a cultivar of this species. Scotch Moss is actually a species all of its own, although it's still part of the Carnation family (Caryophyllaceae). It's sometimes also referred to as Moss Sandwort.
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 footfall isn't too heavy.
This fully hardy, dense and low-growing ground cover reaches a uniform height of about one inch with an eight to ten inch spread. Scotch moss offers a golden-green shade rather than the bright green seen in the more widely available Irish Moss. Also, the tiny white flowers that begin to bloom in late spring develop in clusters rather than individually.
|Botanical Name||Arenaria verna|
|Common Name||Scottish Moss, Moss Sandwort|
|Plant Type||Prostrate herbaceous evergreen perennial|
|Mature Size||2 inches in height but spreads widely|
|Sun Exposure||Full Sun/ Partial Shade|
|Soil Type||Variety including sandy, loamy and chalky|
|Soil pH||Not particular|
|Bloom Time||Late spring to early summer|
|Hardiness Zones||4 to 8|
How to Grow Scotch Moss
Don't expect Scotch Moss to thrive in shaded, damp conditions like a true moss species will. They will not thrive in intense heat.
If this plant is grown in a temperate climate, in a good-quality soil, and in a sunny or partial shade position, it's likely to do well without much maintenance.
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. It can start grow irregularly giving it a unattractive undulating appearance.
Scotch Moss prefers a fertile, moist soil. It can manage in sandy, loamy and chalky varieties, but if the soil isn't particularly fertile, it may benefit from having additional organic matter added.
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. Brown patches can be a problem for this species.
It isn't a drought-tolerant plant, and the soil should, ideally, be kept consistently moist without becoming 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 additional feeding. For less rich soils, an annual feeding in the spring could 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.
Propagating Scotch Moss
Scotch Moss is easy to propagate. It takes little effort to lift out clumps, or you can cut a section out. This can then be divided up to replant in the spring or summer, providing the piece has sufficient roots attached.
This isn't just helpful for populating other areas in the garden. These divisions can be used to replace areas of Scotch Moss that have become overly brown too.
Although it's relatively slow-growing, because it's self-seeding, once well-established, Scotch Moss can get overcrowded. This can contribute to mounds forming.
Dividing the clumps at this point will help ensure the ground cover can grow to the best advantage.
Growing From Seeds
Providing the seeds get plenty of warmth and direct sun, and that they're kept moist, they will germinate easily.
You can sow the seeds in trays indoors and then transplant them outside in the spring after the hard frosts have passed.
The other option is to sow them outdoors when the temperatures are mild enough.
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 becoming a problem.
Irish and Scotch Moss, Sagina Subulate and Arenaria Verna. University of Wisconsin-Madison Division of Extension.