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