Kill dark plants in forest is a mission in Jak 3. Samos Hagai had gotten reports of a dark eco infestation in Southern Haven Forest and with Jak nearby he tasked him to go in as well as taking out any infected plants he could find.
The PlayStation 3 and Vita versions of this mission are related to a trophy named "Black Thumb Too", completing this mission will reward you with a bronze trophy.
The forest is infested with a strange form of plant growth which can only be destroyed by dispersing green eco over them which you can collect with the JET-Board. Both the green eco vents as well as the plants are marked on the mini-map, so travel back and forth and get rid of all of them, they won't regrow more plants either. You can also use the button to dispense a larger amount of green eco in a small area around you.
Some areas of the forest are infested with pod spiders, do not stand still with these buggers around. You can kill them with the jet board but it's easier to just avoid them as they will respawn endlessly. After completing this mission you will automatically proceed with the next one; "Destroy eco grid with Jinx".
- This mission is very similar to Cure dark eco infected plants, a mission from Jak and Daxter: The Precursor Legacy