Rob Davison expounded:

Bit sweeping. We've had one for 30 odd years. Never seen a seedpod or
(unsurprisingly) a seedling in all of that time. It'll be better
than 30 feet high.

Same thing here, there's one the next town over, only one I've ever
seen around here. They're not hardy enough around here to get very
invasive (which doesn't take away from the fact they are a horrid weed
tree in warmer areas of the country).

--
Ann, Gardening in zone 6a
Just south of Boston, MA
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