when i change the size of a tree in the hierarchy and then drop it into the terrain tree placer the size of the tree changes to the original size of the tree before I edited the scale
how can I have it so the trees stay the same scale i have edited them to in the terrain editor?
Go to import settings and change the “Scale factor” to your own value.
Drag a tree onto the scene, adjust it how you like it. Now, in one of your project folders right click and select create new prefab. Drag the tree from the scene on top of the prefab. Now when you want a tree like that drag the prefab onto the scene. If you’re using the terrain editor to add the trees you just need to add the prefab to the terrain editor list of trees
check this 1 in scaling your procedural trees in terrain.