Here's a closeup of the leaves.

looks like a type of ash, black walnut? Maybe even tree of heaven? These species are very invasive

well?? ... just to cover the apprentices shotgun.. how about elm .. lol ...

ken

Appreciate the guesses (ash, walnut, and tree of heaven), but eliminated those due to alternating leaves. Otherwise is does really resemble black walnut or the tree of heaven in overall shape. Looked at too many elm pictures and my eyes went crossed... elms are at least alternating like this one, but none of the overall tree shape or branching seems to match (though I could definitely be overlooking something).

It won't be any of those, all I can think of is maybe one of the species of Koelreuteria. The parent tree(s) will be nearby somewhere, with the fruits (in season) that are making the seeding into your plantings possible. More developed specimens with flowers or fruits will be easier to identify.

Are those compound leaves? If so, it looks like they have opposite arrangement. I'd say bboy has the closest idea.

Koelreuteria elegans (golden rain tree) looks like a good match. I had looked at that earlier but the leaf shape and branch formation of the adult I was comparing it to did not seem to match; the sapling stage photos I'm finding do seem to resemble it well.

Now that I know what the parent tree looks like, I'll try to find the parent tree. We do get a range of seed dispersing wildlife, though, so it may not be anything within a short distance. It may be something a few doors down landscaped into someone's yard that I've never noticed or something a mile away. It doesn't read like something I want growing as close as it is to the screened enclosure and brick wall that it's adjacent, too, so... it may not matter what it is, it's likely coming down... now the only questions is do I replant it considering it's likely invasive, etc.

And after further looking at photos of the adult stage in bloom, I believe there are at least 2 of these within this area... thanks for the help identifying this twiggy pole!

I vote for eliminating the golden rain tree. They're horribly invasive and there are several next door to me, and I'm always fighting the seedlings. Someone wanted me to dig up one of the seedlings and bring it to her because she likes the tree, and I wouldn't do it.