One of our favourite plants for difficult shady spots is Brunnera macrophylla ‘Jack Frost’.  It works particularly well at the base of hedges or trees where the foliage really stands out.  Grown for its foliage that appears in the early spring and stays until the winter sets in.  In the spring dainty blue forget-me-not type flowers appear on slender stems.

Plant in drifts for maximum impact.