I think it's an upgraded Iceberg Lettuce. Maybe it freezes zombies, but freezes them in a block of ice like the ice blocks from Frostbite Caves.
Maybe it a gold bloom which can freeze zombies
they look similar
Views06 Is somewhat right. Yes it does freeze zombies in blocks that the player can plant on. Ice bloom also has a 3x3 thing too. Ice bloom freezes all zombies on screen but will be more effective around the 3x3 area it was planted in.
Pretty decent plant
Freezes all zombies in screen, zombies freeze in blocks (in a 3x3 area). These blocks kill zombies inside, and other zombies eat on the blocks like Wall-Nut, to stall the zombies.
ice shroom
the end
the end