Update: a search seems to show this is a silver maple. So now my question is, what are those "silver maples" folks planted back in the 50s and 60s (to their regret) that had much smaller very silvery leaves, and they sprout up ALL over your yard, especially if the tree is removed? Is that one also a real "silver" maple or something else?
TIA
Nigell

Maybe in the first location they do not grow as well. Do the leaves etc. look the same otherwise?

No, the silver maples that sucker have a very silver shimmery leaf. This silver maple has plain green dissected leaves. And the one that suckers has smooth bark.

Silver Poplar sucker, not Silver Maple.

Here is a link that might be useful: Silver Poplar, Populus alba

Yes, if the other kind pops up to form thickets and the leaf is not just like that of silver maple only smaller, but instead different then the obvious candidate is white poplar. Others asking here about it have also called it a maple.

Yes, that looks like it silver poplar. In New England when I was growing up they called them silver maple trees. Why I don't know. Not a tree I'd want to have around.
Thanks folks!
Nigell

Would be due to the maple-like leaf outline. Most kinds of poplar do not produce lobed leaves.