Added - Planter 1 and plant 1 are working now. May contain bugs, please report.
Mechanics:
Plant a seed in a planter and watch it grow
Remove the seed at any time, it will destroy the plant, but return your seed.
Once fully grown you can harvest fruits. You do not need to harvest all, just grab a snack and leave the others, they will be saved (but harvest the plant first if you want to remove the seed!)