Bloodthirsty Vegetation is one of nine optional trophy quests. This quest is obtained killing the coccacidium, a vicious archespore that Vincent Meis is offering a reward for. Only one trophy quest, The Beast of the Sewers, is not optional, making a total of ten.
Walkthrough
Geralt acquires this quest by slicing and dicing this overgrown asparagus in his travels through the Swamp. After slaying the Beast of the Sewers, he consults Vincent Meis for a list of other monsters which fetch a good price, and this plant is at the top of the captain's list.
After the witcher has slain the plant, he returns to town to present the trophy head to Vincent for a nice reward.
Notes
- This plant can spawn in a few places, see the notes section of the Coccacidium entry for a list.
- Unlike most other trophy monsters which are worth XP similar to their non-unique counterparts, the coccacidium is worth approximately 2000 XP (exactly 2000 XP at level 19, +5 XP per each level less than 19) for the kill on top of the 3000 XP quest reward, so the total rises to 5000 XP.
Phases
Archespore
I have proof of having killed the archespore. I should take it to Vincent. I need to get the proof of having killed the archespore to Vincent.
A Reward
- this phase only happens if you fail to turn in the trophy head in Act II
Vincent no longer holds the key to the coffer. I need to see the Royal Huntsman about my reward. Vincent no longer disburses rewards. I need to find the Royal Huntsman.
A Reward
I killed a very dangerous plant in the swamp. My pouch is now heavier by 400 orens. I received my reward for the trophy. (400 
+ 3000 XP)