Nice idea, I like it, if we all put our thinking caps on, we could definitely come with so many ideas.
I'm brainstorming now lol, for a while I've been thinking of a plant that could temporarily mind control zombies that are caught in a force field type thing, similar to Night Cap, the difference is it's hard for zombies to know if they're caught in it because it doesn't have any other effects, but zombies that are caught in it, are mind controlled into thinking all zombies within 10 metres are Plants, it only lasts 6 seconds but lingers an extra 2 seconds when zombies leave the force field or it closes, another ability would be, and this is where I think it should be a lemon 🍋, lemon shoots pips that attach to zombies, growing all over the zombie, slowing them down and any other zombie right next to the affected zombie, also get caught in it, making the affect last longer and with an upgraded ability, causing them to get stuck together, meaning a Chomper could swoop in (underground) and swallow 2 zombies at once, third ability, acid juice, Lemon shoots his juice, it forms a puddle on the ground, causes major burn damage to any zombies that run thru it, when a zombie gets hit directly, as he runs, it leaves an acid trail along the ground which can affect other zombies.