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