This one really was a poplar.
On Sunday I went on a guided tour of the Hammond Arboretum at Robert Smyth School. There were any number of beautiful and fascinating trees there, but, inevitably, my eye was attracted to this. Apparently it (a Prince Eugene Poplar) used to be the tallest tree in Leicestershire, before it caught a disease that made it turn completely white. The guide described it (I think) as having had a spectral appearance in its later years.