Q.Orange Marks On Raised Border Coping Stones
We have several raised borders all of which seem to be suffering rather UN-sightly orange marks on the coping slabs. Sunshine appears to reduce it slightly but we are wondering what it is and how best we can clean it off. Can anybody help ?
Certified GKH Gardening Expert
This is an actual case of rust! This happens when there is a high iron content in, either, the stones, or the water or soil touching them.
From here, it is advised to use soap and water to avoid damaging the concrete. If that doesn't work, then citric acid can. Just be cautious with this, since it can corrode the concrete if used in excess.