Plant Growth Period is also known as the 'Day Cycle'
<dayCycle>3</dayCycle> <!-- Real life hours per in game day. Affects speed of crops and trees growth (range: 0.5 - 24) -->
- Crops have 8 growth cycles before they are fully grown.
- When fully grown, crops die in a third of the time.
So on the default '3 hour day cycle' Crops take 24 real life hours to grow and you have to harvest them in 8 hours. (3 hours x 8 cycles = 24)
When set to 0,5 (or 5 in your own world creation). They take 4 hours to grow and die in 1.33 hours.
When set to 24 (or 240 in your own world creation). They take 192 hours to grow and die in 64 hours.