Equi-Flower

Equi-Flower shoots "evil" sun at zombies, doing 1.5nd each. While it shoots evil sun, it also produces sun for you.

Suburban Almanac Entry
Equi-Flower has a problem. Her evil side doesn't want to produce sun, but her normal side wants to. They decided to shoot sun AND produce sun.

Plant Food
Equi-Flower shoots a giant evil sun (doing 15nd) and then produces lots of sun like a Sunflower.

Strategies
It isn't recommended to be the sun-producing plant at the very start due to its expensive cost, but later you can always replace the sun-producing plants with Equi-Flower.