Janka Hardness Rating 1260 - Red Birch refers to the heartwood stock of the Birch tree (Yellow Birch is the sapwood of the Birch Tree.) It is generally a golden brown color with some red undertones. Red Birch has slight color variation from board to board and it’s graining is generally fine with uniform curls. Some boards may appear to be almost clear with little to no graining at all.