Hi floral

re cuttings: sorry, we were travelling, I just grabbed it to take pics.

re seedlings: I have been gardening vor more than 20 years, on sandy and loamy soil, but cant remember finding a Forsythia seedling, lets see, what others detect, have a nice day,

bye, Lin

Looking at images of Forsythia foliage turns up quite a few similar leaves. https://davesgarden.com/guides/pf/showimage/410523/#b 

I wonder how it got there? It roots so easily maybe it started as a dropped pruning or something.

If it were over here I would say Physocarpus.

The kind of Physocarpus with opposite foliage??? 😉

🤗 Yes, we have them, you know... Very rare

I had to look it up, but exactly what floral said about the opposite foliage.

I posted it on a German site with little hope, uploading pics is cumbersome overthere,

but

added to write, sorry, so floral, there seem to be similar information structres (or likemindedness?) as I was shown the same link from the German forum like the one you posted... ;-)

there are some fellow nerds, and one was online today and suggested a Forsythia species (or hybrid thereof),

Forsythia suspensa or similar

Pics of foliage at Daves garden

so far this is the best fit IMO. The twig and bark had my brain come up with "Forsythia", and that might be the reason why,

it grew at a tram station from some joints between stone slabs/ paving, so my guess was seedling. Dont know whether hybrids would set seeds, but with species it would be more likely, wouldnt it?

This reminds me of my Forsythia intermedia tremonii, which may actually more accurately be F. 'Tremonia'. I bought it as the former, but online it seems to be more often called the latter. In any case, its common name is cutleaf forsythia. I bought it because it has pastel yellow blooms, rather than sulphur/screaming yellow. But the leaves of mine are very similar to your photo. I have never seen a seedling from mine, but it has set seeds in some years. Also, the spotted/warty stems in your photo say forsythia to me, as well as the axillary buds.

The only good photo I could find is here (click the thumbnail to enlarge):

Forsythia tremonii or F. 'Tremonia'?