This is lovely. Do you think the Irish moss can survive in Southern California, where temps can get high for about 4 months, but nice otherwise?

Thanks for the question. It would grow, there is a good chance that it will brown out to some degree during the hottest summer months and then green up as it cools in the autumn. You might be able to lessen the stress by putting it in an area where it gets some shade, especially from hot mid day sun.

In our area they are sold as "New England fieldstone steppers."