I'd like to point something out to anybody going for this. If you use the chemicals in the plant room (not the boss, the one with the fountain, where you get a death mask in the mansion) and cause the herbs to wither, it DOES NOT count against this trophy. I turned the valve the wrong way, 'destroyed' the herbs and spent the rest of the game wondering if I still qualified for getting the trophy. But upon finding everything else and walking out onto the helipad I still got the trophy! So if you destroyed the plants like me, don't worry, you can still get the trophy.