Complete Seeing Stars before the first wave zombie appear.
1. Make sure you first choose Sunflower and Potato Mine. It's up to you to choose the other plants.
2. Fill up the first lane first with Sunflower. Use the potato mine to kill the first zombies that would appear. The cost of Potato Mine is lower so it will save sun for later.
3. When you are finish with the first lane, start saving sun for the Starfruit and start planting it. Continue planting the Sunflower though as this will help you gain more sun for the Starfruit.