Thanks Paul, good to know. I've top-dressed with compost every time I visited, usually spring and fall. We've got good wood chip mulch everywhere, and have also given it regular Miracle-Gro but not the acid type. Will try that.
My daughter's yard is like your friend's, in some places it's a lot more alkaline than others. I'm blaming the contractor who built her house (they bought it new) because when we started planting the garden we'd find spots all over the place where they'd dumped gravel, concrete, leftover mortar from the tile, and other trash. Plus he spread the subsoil that they dug out to make the basement all over the yard as well. About 30 pickup loads of compost from the dump later we actually had soil that would support life, at least in some spots. But then the bigger plants with deep roots would reach down through the amended soil and sometimes hit that icky subsoil. We'd know because as with your friend, one plant would be discolored, and the one next to it would be fine.
I'm assuming that's what's happened with this poor Tree Peony. It's surviving from all the tlc it's getting, but still extending its roots into whatever is below the original planting depth.
