. All you need to do is collect the coins and replace the Garlic after each wave. It's straightforward, but make sure you've got enough. As per the Plants vs zombies wiki: Extra Seed Slot ten - $80, (unavailable on iOS, Mobiles with Samsung bada OS, DS, and Android because. When will I be able to purchase this? Just buy them. You must first buy the seventh ($), eighth ($), and ninth ($20,) seed slots. One extra seed slot can be obtained in Pirate Seas, in a gate between Day 9 and Day 10 before the update or by completing Day 21 after the update. All together, it costs $, to get all 10 seed slots. Note: This strategy will not. You need to purchase each slot one by one until the 10th becomes available. seed slots plants vs zombies. In Crazy Dave's car I see the slot being sold for $80, but it has a sold out sign over it. The. Example This strategy only needs 7 seed slots.