Not certain but it looks like the birds might have brought you a young plum tree

My first reaction was that it might be a blackthorn, so much the same conclusion as you, Inverglen.

"Weed tree" - heave it out is my advice. And before its roots get too long. Unless you've got the sort of garden that needs a thicket, of course!

Yup! Can't argue with that, Beattie - we get quite a few growing and they're a bit of a nuisance.

We get them too - ash seedlings, blackthorn and other wild plums, willows of various sorts, sycamores. Oaks from acorns planted by jays or squirrels. I pull them all out or we'd have scrub instead of a garden in no time.

It looks like a prunus of some sort..& yes,as others have suggested,dont get sentimental over them,yank them out before they set too well...the advice I ought to have given myself years ago with a common willow self setter! Ash, & sycamore are a thorough nuisance round here too if not detected & dealt with in time.

Thank you to all for your answers,very helpful.
I'll let her grow a bit more and see what it is as I am quite curious now.

The roots grow deeper and quicker than the top growth Coffeebean. If you leave it now, it'll be really hard to get out later. It's a blackthorn, so unless you want one of those, where this one is growing, I'd strongly recommend that you pull it out ASAP.

If you want to see what it is why not pot it up and grow it on?

Yes,you are right. I was thinking the same, to move it in a large pot and wait. Thanks anyway.