What are these seedlings in my nectarine tree pot?

[Oldnews]

I'm a proper novice gardener, and I've recently bought a nectarine tree which I've got in a pot. It's not doing very well and we've been refunded. I've sown forget me nots round it, but noticed these little seedlings sprouting up. They're also in my potted clematis but no where else.

Does anyone know what they are? Are they just a type of weed?

Thank you!

Could be a Hazel tree seedling. They self seed easily. They grow rapidly too but if you put in a pot you can prune it into a nice shrub or bush.

Not hazel, wrong shaped leaf. But I don’t know what it is. I’d pot one up and grow it on a bit