Steps:

1. Enter Farmville 2

2. Open Cheat Engine

3. Select processs (flashplugin.exe for firefox and chrome.exe for chrome)

4. Change value type to "Text" / "String"

5. First scan "obstruction_rock" (all the rocks)

6. Select all the results and press the red arrow

7. New scan "obstruction_stump" (wood)

8. Select all the results and press the red arrow

9. Now, select all the addresses in the table below (Ctrl+A)

10. Change all the values to "e_deco_shrub-round"

11. Go back to your game, visit neighbor, and go back to your farm.

12. ALL the rocks and stumps will disappear. 

13. You no longer need the pickaxes =D w