There is a berry farming island on Poke Pelago which you can develop. It's called Isles Aplenny. First Rank lets you plant 6 berries. Second Rank lets you plant 12 berries. Third lets you plant 18. The time it takes to grow is dependent on what berry you plant. Each plant harvest about 6 berries on the first stage, 10 on the second, and 15 on the third.
Source
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