Christian teaching is full of references to trees, The Tree of the Cross, The Tree of Life, Jesus homeland was refered to in Deuteronomy as "a land of Olive Trees," and, of course, Jesus is refered to as a carpenter.
Almost half the world's forests are now gone, and with deforestation even this figure is dwindling daily. So why not plant a tree? Plant as a commemoration of a special event, a birth, (so the child and the tree can grow together) an anniversary, a birthday as a thanksgiving or as a memorial to someone.
If you can, chose a local variety tree, so the indigenous wildlife will thrive upon it. If you don't have a garden, is there a place nearby where you can plant one and help to break free of the Tarmac, Asphalt and plastic culture of today's world?
I remember when I was about ten, a girl in my class at school, whose parents had no real garden, planted a tree in the local park for her, and no, they did not ask if they could! My fellow classmate was so exited over the years about 'her' tree that had now grown and was doing well. I have often wondered if she took her children and perhaps now takes her grandchildren to see the living proof of their great grandparents love for her.