Betula nana Betula nana Betula nana, the dwarf birch, is a species of birch in the family Betulaceae, found mainly in the tundra of the Arctic region. It is a monoecious shrub growing up to 1–1.2 m high. The bark is non-peeling and shiny red-copper colored. The leaves are rounded, 6–20 mm diameter, with a bluntly toothed margin. The leaves are a darker green on their upper surface. Leaf growth occurs after snow melt and become red in autumn. The wind-pollinated fruiting catkins are erect, 5–15 mm long and 4–10 mm broad. "Betula nana" is native to arctic and cool temperate regions
Beech bark disease to spread to the south and west. The first case of beech bark disease in the United States was reported in 1929 in Massachusetts. By 2004, the disease had spread as far west as Michigan and as far south as western North Carolina. For beech bark disease to occur, two components are required, an insect and a fungus. The beech scale insect, "Cryptococcus fagisuga", is invasive to North America and is host-specific, feeding exclusively on beech trees. It can be observed on the trunk and limbs of the tree as woolly, white tufts that will later develop into broad strips.