Question: Is it virtuous to plant a tree?

Answer: Yes, one will attain reward for planting a tree if one makes a good intention.  

Anas Radiyallahu Anhu reports that the Messenger Sallallahu Alaihi Wasallam said, "If a Muslim plants a tree or sows seeds, and then a bird, or a person or an animal eats from it, it is regarded as a charitable gift (sadaqah) for him." (Bukhari)

AND ALLAH KNOWS BEST