"david" wrote
I planted a tree peony a few months ago and all looked well, now all the
leaves are falling off - is this normal for the season or do I have a
problem?

Yes, it's normal and possibly but not necessarily.
Does it have healthy buds where the leaves are falling off from?
These buds should swell considerably at the end of winter, if they don't you
have a problem.

--
Regards
Bob H
17mls W. of London.UK