Recommended Plants: Sunflower, Puff Shroom, Potato Mine, Wall-nut, Peashooter, and Snow Pea
Level 2-1 begins with Crazy Dave explaining that fighting zombies during the night is very different from fighting zombies during the day. Sun does not drop out of the sky randomly, though Sunflowers will still produce sun. The newest item in the arsenal is the Puff Shroom, which you obtain by defeating stage 1-10. It has incredibly poor range, but it is completely free.
Simply put down a sunflower and a Puff Shroom right away. You will be able to put down two Puff Shrooms before a zombie shows up. Keep putting these little mushrooms down as fast as you can because the only thing limiting your usage of them is the cool-down timer on the seed card. I will often have three or four in a row, and the zombies on this board are weak enough that you really will not need much defense. Be on the watch out for gravestones. In the last wave, all gravestones on a board will spawn an additional zombie. Thus, if you have a row with several grave stones, make sure that one is well fortified and defended. At the end of this board, you receive the Sun-shroom.
Coins begin dropping on this board. Make sure that you click on them to pick them up when they drop. You have a limited time before they despawn.