Go to Tiquanda Laboratory! My character is there right now. See where is the place from Port Hope:
Go -2, and move to the left from the ladder that you used to reach this floor. You will find this room:
Use a fire field rune on every Spit Nettle after you kill them! Once you do that, rotate at the rooms there (you can do Mutated Human, Carniphila, Haunted Treeling or Swampling bestiary all together!!!).
The damage of fire can be your "alarm" to return to the room and use a Great Fireball Rune! I do that because although the fire field can kill the Spit Nettles, these plants gonna use a weak healing and will make this process less rapid!
Why you should go there at my recommendation instead of any other place?
Simply because you are near to Port Hope, the place is super easy to reach (no access required) and also because you can do some other bestiaries at the same time!