btw 'tree of heaven' is another close thing I came up with as a guess, but it doesn't quite look right for that, either

Sambucus sp. There are also grape seedlings and I’d guess this is a bird perching spot. Btw Note that the leaf arrangement is opposite which precludes Ailanthus.

On further examination I believe there are some Rubus there too. More bird work.

Thanks very much. I've seen the natives ones in other parts of Maryland but not around here. The birds, though, will do what they do. Many many years ago I had a S. nigra f. laciniata in the garden, but I don't think it ever got to the point of fruiting. But it's been gone for at least 10 years so unlikely seed from it would be sprouting now. Its foliage was a darker, glossier green which I assume applies generally to S. nigra and this must be a native one.

Yeah my garden has scads of Rubus seedings - both native and 'invasive' - and wild grape seedlings. #1 weed seedling is sadly Celastrus orbiculatus since there are morons around here who have let it engulf their entire gardens. At least they are easy to pull when small.