The house I moved into this spring has a beautiful magnolia tree in
the back yard but there is essentially no grass under the tree. It
was a little sunken and I filled with top soil and reseeded with a
shade mix early in the summer. The grass came in well but then died.
We had a fairly wet summer and I didn't fertilize after the starter
fertilizer so I don't think I "burned" it. I checked the pH and it's
nearly neutral. Is there something about magnolias that would keep
the grass from growing well?

Also, there's one branch that's a bit low and I'd like to prune it.
Should I do that in the fall or the spring?