Irish and Scotch Moss
Location: Fremont, CA
Question: I have a Japanese garden in which I'm trying to grow Irish and Scotch moss in the spaces between boulders (which have been filled with soil). I fertilize sparingly in the spring with 5-5-5 or diluted fish oil. The soil is kept reasonably moist and the location receives filtered sun in the morning and near full sun in the afternoon. I have 3 questions. 1. How do I get it to self-sow? 2. In some locations the moss picks up a subtle browning and then dies about 2 months later. What could cause this and is there a remedy? 3. How do I determine by looking at the moss if I'm over or under feeding?
Answer: Sagina subulata and Arenaria verna, Irish and Scotch Moss, are two different plants with similar appearance. Both make dense, compact, mosslike masses of slender leaves on slender stems. While both resemble moss, their growing requirements are quite different from the moist, shady conditions under which true mosses thrive. Both Irish and Scotch Moss produce tiny flowers which develop seeds. In fact, they can self-sow to the point where they become pests in the garden. If yours are not self-sowing, there may be a cultural problem preventing this. Your plants should grow well in full sun to partial shade, with regular water. They require good soil and excellent drainage. The browning of your plants might indicate overly moist soil conditions and the development of a fungal disease. Dig out the affected plant parts and adjust your watering practices. Instead of keeping the soil constantly moist, allow it to dry out a bit between waterings. The plants are not heavy feeders and too much nitrogen will cause the foliage to grow into mounds rather than to create a low carpet. One fertilizer application in the spring and another in the late summer should keep your plants growing at just the right rate. In my garden I propagate Scotch Moss by cutting 1"-2" strips from established plantings and replanting them. The empty spaces fill in rapidly and I think it helps to prevent overcrowding of the existing plants. Hope this information helps!