Lombardy Poplar Tree - Suffers a Setback (Frost? Transplant Shock?

A couple of weeks ago, we planted a fast-growing Lombardy Poplar tree in our far backyard and had high hopes that it would provide a little bit of screening in a quick way.  But, today I went by to inspect the tree a little and was surprised to see it was having some trouble.  Look at the photo above to see the leaves that are wilting and browning out. 

This is certainly NOT a good sign, but I'm not calling it yet with this tree and I hope it can bounce back.  I'm pretty certain that this was a recently-planted bareroot tree that came in a burlap sack.  This was the first tree that we received in one of those burlap sacks and I decided to NOT plant the sack.  I think that was a mistake. 

It *could* be frost damage like what we've seen on some of our ferns, but I'm not sure. 

On the next tree - which I'll post about soon, I trimmed the burlap sack down to be pretty small and planted the sack to try to keep the soil around the tree roots a bit more. 

I'll be watching this tree; as there is currently plenty of green underneath the bark, but limited leaf growth.  This tree has a 365 day warranty, but I believe that I'll have to get to this by the Summer/Fall in terms of determining how it is doing because we bought these early in the season that I'm not sure we'll see budding out next year before the warranty expires. 

For record keeping purposes, I'm going to check the box on #24 of my to-do list for this season:  plant a columnar tree.