In zone 6b/7a here in SE PA it grows very well but is not invasive. I
have never seen it spread by seed, and I could not get cuttings to
root. I have bought the three that I have at a local garden center. I
was not even sure it would grow well here, but then I saw one out on
the main road outside of an old farm house. It was 20 feet tall and
very old and interestingly twisted.