I'd already been all the way through PvZ on my iPhone before the zen garden upgrade. I've continued playing, farming coins to unlock minigames, etc. However, the game seems to have entirely stopped giving me new plants. I've resorted to buying them expensively from the new store options.
How do I get more plants for my Zen Garden? talks about 'survival' mode, but I don't see that anywhere on my phone. Does it have some other name, or is it not in the mobile version?