This is an extremely aggressive and variable species or 'complex' and research by Tom Volk and others suggests that what we call Armillaria mellea may be several different species. In any case, what all they all seem to have in common are the blackish hairs on the central portion of the tannish-ochre cap, a fibrous and tough stipe, a prominant white ring formed from a partial veil, whitish spores and growth on wood.