So we it takes 9 minutes to grow the first batch and then 3 minutes each of the two remaining lines to grow next batch?
Yes. Remember the time intervals between each plant
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After 6 minutes if growing
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Knock them all down to form this ( each plant here takes 3 seconds)
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After more growing
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Knock them down again to get this
- - - - - - - - - - - - - - - - - - - - - - - and so on
You start with 3
Each time you plant a fresh one it takes 3 seconds, and after three minutes it grows one block then you follow above diagram