Planting Irish Moss

Asked May 27, 2020, 2:09 PM EDT

I will be planting Irish Moss between paving stones and I am wondering how to prepare the soil before hand. I don’t have enough moss to cover all the area so can I cut up the 4 inch potted plants into plugs, maybe 4per pot? The soil that is there now is pretty much decomposed bark dust with not much in the way of nutrients in it. What should I mix into the soil and would it be prudent to add a pre-emergent herbicide like Preen to keep the weeds out while the moss is growing together? I assume the moss doesn’t spread by seed? Would the Preen hurt the moss at all? Thanks so much for your feedback. I live in Tigard in Washington County.

Washington County Oregon

5 Responses

Actually I just planted this type of moss adjacent to front yard pavers. Breaking the plant up into smaller "plugs" should help the spread. When I planted I used a mix composed of inexpensive topsoil available from ACE hardware combined with quarter minus gravel (50#) from Oregon Decorative Rock or any local nursery store. I added fertilizer as well and watered this all in. Preen has two weed preventers one organic and the other is not. If in doubt about using weed preventers just use the fertilizer. The app "Grow Safe Grow Smart" is an invaluable tool for selecting safe lawn and garden products for future reference.

Thanks, Jack, for the speedy reply. Since I now understand that Irish moss does spread also by seed, I have decided that Preen wouldn't work anyway. Is using the quarter minus gravel for good drainage? Was it a half soil, half gravel mixture that you used? I have read that it should be fertilized every other month with a 10-10-10 fertilizer. Would you recommend a liquid over granular fertilizer?
Thanks again, Jack!

Quarter minus gravel is what landscapers use between pave stones. One to one mix is fine: use enough soil so the plants can be seated firmly. Osmocote is a good fertilizer particle style that breaks down slowly over time and won’t drain through the soil gravel mix quickly.

I promise this is the last question regarding the Irish moss. I understand the logic of using the Osmocote 10-10-10 to mix with the quarter minus gravel and soil when planting the moss, but when I fertilize it later, won't the Osmocote just sit on top of the dense moss and not dissolve in to it or the soil below it?

Osmocote is water soluable, works well in the heat, and will eventually break down and do its job. However if you prefer to hit the new plants more quickly then by allmeans use the liquid variety. In this heat my thinking was that between evaporation and drainage through the gravel mix the new planting might be short changed with the liquid fertilizer. Moss will likely grow and even thrive no matter what you do with these optimal growing conditions.