Replacing front yard trees
I have a 75 ft front city lot (South 10ft, drive 30ft, North 35ft). I have two large mature Ash trees on the main and North side of the house. It faces East. I do not want to take them down yet but I would like to begin replacing them so I have a more mature tree when I do take them down. I do not feel like I have much room. How far away do I need to plant the new tree? Do I need to take an Ash down? Other advice? The yard is about 25ft deep.
Also, I am looking at a Black or Honey Locust or a Tulip tree. Any other ideas advice or input?