Irish moss is not a moss. It is a vascular plant. Scotch moss is also a vascular plant. If you read to the very fine print the plant tag probably acknowledges this detail.

However, there are certain types of bryophytes (mosses) that prefer a limestone substrate that would work in the cracks between your stones... and Bryum argenteum is a great solution on gravel, asphalt or concrete surfaces... common name is even "sidewalk moss."

Ok, so I have to admit I feel a little stupid. For years I have been intrigued and have admired the beauty of different mosses but obviously know nothing about them. It is now my mission to learn more about them, thank you for that inspiration. Thank you also for the recommendation.

Irish and Scotch moss are among other tricksters like Spanish moss (pineapple family), club moss (lichopodium), reindeer moss (lichen). And, unfortunately, there is no true ID guide to bryophytes (mosses). In an effort to promote the awareness and appreciation of mosses, I have a web site you might wish to visit... mountainmoss.org. I have lots of new photos to create a new section... planning an ID gallery to enhance the current info. Hope to upload them in a few days. I am not a botanist or bryologist, just a serious moss lover. I continue to research and network to learn more myself... happy to share!

Thanks so much. I will definitely check it out!