Ailanthus

Ailanthus Altissima, called either Tree of Heaven or Slum Palm, is a tree that thrives in places where no respectable plant would grow: in vacant lots,  between the broken glass in alleys,  up through rubble and  cracks in the sidewalk.  It is widely considered an urban blight, an ugly invasive eye sore, and because of its tenacity, campaigns to rip it from the face of the planet are ongoing and expensive.  But there are others out there who praise the Ailanthus for standing up to the asphalt and concrete and bringing a bit of welcome shade and greenery,  a little oasis for passersby.  So what is Ailanthus?  Occasional oasis or tenacious blight?  And which will its spin-off Ailantha be?