Mosses have some great uses in the garden. They are only regarded as weeds when growing in the ‘wrong’ place.
Moss is often regarded as a weed when it is growing in a lawn, on the roof, in the driveway, etc. where it is unsightly, is inappropriate or causes problems with drainage or surface damage. See here for more about moss as a weed.
But moss has its good side. It can give a wonderful effect in a shaded and damp area of a garden as in my brother’s garden shown in the photo above. It can also give a cottage garden effect when growing between pavers or bricks in paths. Moss can also be used to line hanging baskets where its green spongy appearance can be both very attractive and provide excellent moisture retention for plants in the baskets.
In my brother’s garden in Ireland the wooded areas around his wonderful garden (Greba Gardens, Greyabbey, Northern Ireland) are densely shaded and poorly draining, plus, the Irish weather keeps the areas damp. He has cleared the areas of weeds and left the moss to grow over the thin soil and over trees and walls. The moss has a sound deadening effect giving an ethereal sensation where one expects to see wood nymphs dancing in the twilight.