I'm a big Zyra player and I played her since she got released July 2012.
Her plants were smarter before, until they "improved" plants targeting, they became completly stupid.
This is one of the few "bugs" her plants have:
Another well known bug is the fact when you cast a spell on a plant, the plant grows, then has a random delay before it starts attacking. Sometimes it's instantly, sometimes it's 2 long seconds.
Other problem when you grow a plant, they spawn then attack an ennemy champion in range if there is one (That is what is supposed to happen after the plant AI changes), they do one AA, then attack a minions, they don't keep attacking the champion. Anothing thing, it's probably normal but still a pain in the behind, they attack him once, and then the champion goes out of range, and it changes it focus. The champion can go back into plants range, doesn't matter, still attacking that creep unless I go to the dangerous AA range with Zyra and AA the enemy champion so finally my plants continues attacking him... until he goes out of range again....
Please fix
plants, I lose tons of damage because of that