How to snap object to terrain after already placed in scene?

I was wondering if it was possible that after i placed like all my trees by objects not using the terrain tool, and other objects it there like a button somewhere that says snap to terrain on y axis or something if so that would really help me out instead of manually trying to align them all to the terrain piece by piece. thank you in advance

I know this is an old post, But for future people looking for this answer, Hold down Control & Shift, then drag from the center of the translate tool.

You can create a script to do a RayCast down on the Start method to position your object on the ground. Something like:

RaycastHit hit = new RaycastHit();
if (Physics.Raycast(transform.position, -transform.up, out hit, Mathf.Infinity)) {
    transform.position = hit.point;

Select all trees and then Hold ā€œVā€ button then hover near a tree edge and move them towards and edge or pivot.