Both Apple and Google have made available high resolution, up to date satellite maps that one can use to locate even relatively small items like trees with very good accuracy. Below are three methods which both require you to be out in the field where the tree is located.
The first method requires you to use your phone with a satellite map (the example uses an iPhone). The second method has you print out the area where the tree is located which you take with you on a clipboard and mark up to show where the tree is in relation to other identifiable items like buildings or other trees. This second method may be useful for locating several trees at once. A third method is similar to the second. If you have a spreadsheet with some new trees and the estimated lat and lon information, you can make a My Map and then print it out and take it to the location. Then you can go to the approximate locations and mark where the trees really are.