Catalpas seem to have very thick surface roots. Mine is now about 18years from seed and I've avoided digging under it. The soil is quite stiff and poorly drained and the surface is becoming mossy and small plants underneath are struggling. Would a good, but not too deep, digging, removal of a lot of the other stuff and then a mulch be a good idea or would the root damage be too much for the tree to survive?
I see a little cyclamen, possibly cilicium disappearing under moss, I know there's a paeony or 2, lots of digitalis lutea, and other odds and sods. Messy is the word that springs to mind. It needs attention.