Our blueberry shrubs have been mulched to a depth of 6 inches with shredded tree leaves from a Norway maple. Note that red maple and beech have been identified as not recommended for mulching blueberry shrubs. The mulch helps to hold moisture around the roots, I don't think that it's really necessary for protection against frost. Our blueberry shrubs seem to be frost hardy, with or without mulch. Others have used pine needles and oak leaves for mulching blueberry shrubs.

I mulched my Blueberry with Grass clipping I save all my Grass Clipping for mulching. some times I mixed with wood chips.

I mulch my bushes with pine straw.