Plant on moss: moss on plant

Yesterday, first day of spring, I had a careful inspection of Wbx. A curious thing was evident. The white clover that has been wandering about Wbx from its first year has taken up residence in the moss on top of the lump of sandstone and seems to have abandoned the ordinary soil altogether.

At the other end one of the coppiced sallow stools (Salix cinerea) has accumulated a thatch of pointed spear-moss (Calliergonella cuspidata), first seen in the box in 2007. This moss is sometimes a major constituent , with creeping willow (Salix repens) of dune slack plant communities. Maybe the moss thinks Wbx is a sand dune.