Continuity mistake: When the lieutenant and the new guy that joined up in season 2 are in the hospital, he reaches for his gun, shoots, and...click. No ammo. The lady then pulls our her gun, slide fully retracted, finger not on the trigger and states "yeah, me too." Thing is - if the slide was already retracted from running out of ammo - wouldn't she already know? I mean, she holstered the pistol. More egregiously, every shot before this, her slide was not retracted, and the pistol was ready to fire, until now, when she suddenly has a retracted slide.
Continuity mistake: When Cassandra is chasing Addie in the woods you can see that she is not wearing her white boots but trainers or flat shoes. When she catches Addie the boots are back on.
Answer: When the plant zombies would attack they would wrap people with the vines and hold them, so they couldn't escape.