You might want to post this in the tree forum rather than the lawn forum. You'll probably get more responses. I'm no expert, but that looks like a large weed to me.

It is not a tree. This is a perennial weed. Get rid of it right away. The seeds on the plant will compound your problem next year.

Thanks everyone for your help. And thanks for the advice about making such posting in tree forum. I will take care of it.

That's Polk salad