I'm trying to get the gardening achievement:
I went through all of the Gardens of Hope (both tiers) and destroyed all the corruptions I could see. But still I am missing one. Does anyone has a clue?
The maps of the cleared areas:
I got this from a Rarity Guide article, which is clearer...
Destroy all the corruption in the Gardens of Hope without leaving the game
There are 27 corruptions in the Garden of Hope. Some players have reported seeing only 26 corruptions, however this might have been a bug. There should be 27. If your quest is bugged, restart it.
You may have gotten the bugged version, or you missed one on the map.
A way to make sure that the bug doesn't happen is to destroy all the corruptions except for the last one, and wait until the achievement is updated to note that you've destroyed 26/27 corruptions (may take few minutes). And only once it's updated to 26 destroy the last one.
The big corruption growths are the ones you need to destroy. Not the small ones (They are noted on the map).
This bugged for me the first two times. Something I noticed was to do this SLOWLY. I noticed when checking the achievements tab that the achievement was slow to update. I ended up doing about 5 each time and taking a 5-10 min break in between, when I got to the last one and verified it was the last I just sat there in game for a bit until it updated to 26/27. Killed the last growth and got the achievement.
Hope this helps.