Irish moss used as a ground  cover or lawn substitute can be planted anytime the ground is not frozen if you purchase potted plants from a nursery. It will need lots of water at planting time but no need to fertilize until spring. Plants sold in containers transplant more easily than plants dug from the ground. Irish moss is a spreader so you can take one plant growing in a four inch pot and cut it into four sections after removing it from the container. Then space these four small sections about six inches apart and they will grow together into one large patch. May the luck of the Irish be with you in this project. Keep growing, Marianne Binetti