Went to Darkroot Garden, did some stuff, died.
Went back and suddenly everything seems completely different. I'm getting mobbed by a group of three plant guys that weren't active till I searched a corpse near them, and they won't deactivate.
Fire is especially useful on them. Try some of the item that enflames your weapon or some pyromancy, if you have it. Stand back, and don't let them do their 'grab' attack. They can hit from beneath you like Starcraft Lurkers, so be careful.