Board Thread:Plants vs. Zombies Wiki Discussion/@comment-5797509-20140421205454/@comment-1764483-20140422215138

Lightning Reeds, in my opinion, are only useful against Zombie Chickens when stuff like Spikes and nuts aren't present as well as in groups. When you get down to it, Bonk Choys, Lightning Reeds, Kernel-pults (maybe), and Gloom-shrooms all have trouble taking down Coneheads ON THEIR OWN, meaning that they work best in groups or in combination with OTHER plants.

But to be honest, I believe that THERE ARE NO USELESS PLANTS, even if they are deprecated later on. I have problem respecting others' opinions, though.