Survival Hard - "No Plants?, No Problem"

This strategy focuses on making the most out of every empty spaces on the lawn and somehow keeping the sun supply at a very safe spot while removing every single plant at the end of every round for any Survival Hard stage.

Although this isn't really seen as an achievement by the game, this strategy can also be tried if you would like to have something challenging to try especially if you already have memorized the survival hard levels and everything is now just a piece of cake.

This strategy focuses on using Instants only in order to finish any Survival Hard Level.

4 Slot Doom Shroom Rotation + Ice Shroom + Imitater Ice Shroom
Ice-shrooms can freeze zombies for 5 seconds and slow them for 20 seconds afterwards for a total of 25 seconds of being slowed, when timed with another Ice-shroom (or Imitater Ice-shroom) then that is equal to 50 seconds and that is enough time in order for the Ice-shroom to recharge and be used again. Therefore, Ice-shrooms and Imitater Ice-shrooms should be enough to slow the zombies in order to keep them inside the AoE of a Doom-shroom.

4 Sunflowers Then 1 Potato Mine
I always make sure to plant the first Potato Mine after I plant 4 sunflowers because I always want to make sure that one Sunflower should be planted everytime it recharges.