Thomas O'Leary Staff asked 16 years ago
Not a horticultural question but still a garden question. I have a patio of indian sandstone which is now quite stained with small black circular discrete marks, almost appearing like a fungus or lichen.The marks are quite random, some stones being affected and others not at all. Despite use of a proprietary patio cleaner and power hosing the stains remain. Have you any suggestions? The run-off is onto grass.Many thanks, Paula