Popular tree

[RJRL]

I cut down a popular tree that was damaged in a storm. I left the stump to feed birds on.
Now I have this new tree rapidly growing that I want to keep but I don't know what to do with it. Keep it the way it is growing, thin it out or what?
Please see my pictures and if you have some advice. I would appreciate it. Thank you.

 

[Jed1124]

Pick the better of the two stems and remove the other. Remove the old trunk as well. You may have to do this a number of times.

 

[ElevatorGuy]

Those leaves look nothing like our poplar here. The old trunk stub has the correct bark, Looks like weeds growing.

 

[Bullseye T&L]

I highly doubt those are weeds. There are different species of poplar. OP is from Canada.

 

[RJRL]

Thank you Jed, I will do that. Your time is appreciated.
RJ