Help with second Cherry tree sprout in same pot

Hi all, I have a Cherry tree it's 3 years old and a second tree has started to grow within the same container I think it's starting to sap the life from the main tree.

I'd really like to separate them whilst keeping them both alive. Any tips on how to do this would be very much appreciated. I'm not an avid gardener so apologies for my lack of gardner slang :D

Thanks!

 

It looks like a root sucker, your cherry tree is probably grafted and that is coming from the root stock.
You need to dig down and find the point where it joins a root, it usually suggested you pull them off, but I would cut as close as possible to the place there it joins the root.

 

Thanks so much I'll give it a go, is there any preferable time of year to do that?

 

I'd do it now.