How do you beat Level 30?

Does anybody know how to beat level 30 on the iPad version? I have been trying to beat the giant rodent that comes out at the end with no luck.

I have been playing for days and cannot figure it out. I tried going back and playing other levels to get more energy because i still need about 30 more suns to get all the plants at full energy. however, it is not awarding me any suns for beating the levels again. I have tried every combination in the lab. For my own sanity I have to stop. Good luck. Please let us know if you figured it out.

By accident, I realized that the cactus does a lot of damage to the boss. I used lots of cacti, peacannons and tomatoes, just putting them in an abc pattern, alternating them. I only upgraded the two peacannons I had near the hole. I didn't upgrade anything else.
I had tried updating as many plants as I could, but it meant less plants and it didn't work. Also, the poison didn't help at all.
Hope this helps someone. This level is frustrating.