How do I know if my plants are already fully grown in Plants vs Zombies?
Each "day" period they should require fewer things to become happy, and fully grown happy plants have a sort of glowing aura that's visible.
a fully grown plant is one that you can sell for 7500 for most plants, 10000 for nighttime and pooltime plants and 3k for daisies
you know you can sell a plant if when you fertilize it it give diamond(s), if it wants bug spray or if it wants to listen to music