At the beginning of the game. As per the Plants vs zombies wiki: Extra Seed Slot ten - $80, (unavailable on iOS, Mobiles with Samsung bada OS, DS, and Android because. The Kernel. All together, it costs $, to get all 10 seed slots. You must first buy the seventh ($), eighth ($), and ninth ($20,) seed slots. They have different designs in each game. Seed slots represent the number of seed packets the player can bring into a level. To get the 10 slots in Plants vs Zombies, you gotta hustle a bit! First off, keep progressing through the Adventure mode. The Wall-nuts and (non-gold) magnets are ditched, replaced with relatively inexpensive Kernel-Pults in Pumpkins. . Still requires 10 seed slots.