I have one tree peony planted in a raised bed of mixed perennials,
whose soil level has gradually sunk in the 10 or so years since we built it. I
guess the organic amendments just rotted away. It really could use like 4 or 5 more inches.
But I would guess that would kill everything in there. Most of the other perennials
(daylilies, liatris, baptisia, meadowsweet) could be lifted and replanted on
top if I really had to. But I don’t want to dig up the tree peony.

If I add a top
dressing of compost in the corner where the peony is, and try just to add a
little every year, would that work?

How sensitive are tree peonies about soil level? I know
herbaceous peonies are picky about not being too deep. Thanks.