This level is the first conveyor-belt level besides Wall-nut Bowling, more specifically, Level 1-5. The player may not be used to this mechanic yet.
This level does not require the usage of Sunflowers.
The player is given lots of Cherry Bombs, which helps to clear out the high amount of zombies easily.
You will be given so many plants in this level that the lawn will be full of plants after a while. When building your defenses, plant weaker plants towards the front with Wall-nuts and Chompers and stronger plants toward the back. Plant one Snow Pea on each lane to slow down the zombies. Potato Mines work well during the early waves, in the center of the board just in case a zombie slips through a weak lane. Later, replace Peashooters with Repeaters in their tile.
Alternatively, you can use a Potato Mine, or a Cherry Bomb if they are clogging up the conveyor belt or if the zombies come too close to the house.
Plants vs. Zombies Wiki has a gallery for Level 1-10.