Can I use vinegar to clean some minor green and black mold off the top few steps of a gigantic stone staircase I have going down a steep slope on the east side of my yard? The top steps are always shaded and they're a little bit slippery this year with mold. I'd like to clean them without using chemicals, if possible. Would vinegar and a pressure wash work?

I don't have any plants on the slope that I'm worried about killing. All that's over there is a very large, well established crabapple and some sort of ugly, blue spruce looking shrub behind the corner of the third garage stall. I don't think much of anything will hurt the tree because it's so big and I couldn't care less if that horrid spruce dies. Still, I'd like to avoid chemical cleaners if I can, since the runoff on that slope is pretty severe and it would probably all end up in the pond beyond the property, which is a wildlife refuge.