background branch fern frond green natural nature pinna pinnae plant Pteridophyta rib texture tree ferns fronds garden spring unroll leaves plants bipinnate habitat moss norway norwegian pteridophytes wild Asplenium England Gloucester Gloucestershire old pinnate spleenwort stone wall fresh leaf countryside montane mountain calm peace Pteridium stem summer Surrey tranquil Cornish cornwall developing english Great Britain growth pteridophyte stems temperate