abstract bark betula pendula bumps dashes deciduous gray grey raised short stripes silver birch silver birch tree smooth texture textured tree tree trunk uneven Betula birch natural nature silver spring background Denmark shadow sunlight white wood branch Canoe birch grass leaf plane plant Plant stem silver wattle trunk woody plant autumn color colour England english fall golden Great Britain London park trees yellow forest fresh green heath heathland leaves path path through the woods Sussex track trail ament brown catkin cylindrical flower cluster female maturing seed cases seed pods seed release silver birch trees wind-pollinated winged-seeds amber bracken copper dead dried ferns footpath landscape russet rusty stems trunks undergrowth woodland