Because I spent I good deal of time talking about two other runes that relate to trees, it only feels appropriate that the only B rune should be talked about.
Berkana is often translated as birch, a tree that most people are probably passingly familiar with. It has white bark, which often is seen peeling off during certain parts of the year, which seems similar to some kinds of paper, and in fact people did use to write on birch bark for somethings and probably still do, I think it is the white bark of most birch trees that probably stands out the most in my mind, as that much stark lack of color is very distinct, especially when it is off set with many green leaves.
The esoteric symbolism of birch and berkana is what is usually focused on. The meanings that I have always ascribed to it is growth, healing, nurturing, becoming, life changes, and liberation. My own meditations and journeys with this rune have pointed to the powerful feminine influence. My own experience of the spirit of Berkana is as the Birch mother, female spirit with pale skin and green hair, who dwells in a endless forest of birch, with light shimmering through the leaves of the forest.
In part of the tree pattern that seems apparent in the runes, Berkana is the world tree as the generative, creative aspect. In the history of the world, the birch was the first tree to emerge in open areas, quickly turning an area that was an open meadow into a forest, and as the glaciers retreated further north, birch trees would continue to follow, while other trees may then fill in the areas that had once been filled with birch. In the Anglo-Saxon rune poem, it is even described as just growing from suckers that the parent tree spread from it. Although now days research has shown that is not actually a birch tree or a member of the betula family, the concept of prodigous generative power carries forward in the rune.