Most literature will indicate it prefers a rich, moist (but not wet) soil. Soils around here do tend to be moist at this time of year but can dry out when we hit our stride of warm, rainless days in summer. I would not consider Irish moss to be especially drought tolerant.

HI Gardengal, that's exactly what my research indicates, which leaves me wondering how often I would need to water the Irish Moss.

Yeah...I might be better off with a drought tolerant perennial such as Globularia cordifolia.

The "moss" needs good conditions including frequent dividing and replanting if you are to maintain a uniform appearance.

I got plenty of space for dividing and replanting. I bought a small flat of Irish Moss for a test to see how much water it needs this summer. If it's too thirsty for my liking, I will replace it with some drought tolerant perennials.