The Ship
The ship is available after level 16. Initially it offers 4 slots for you to fill with produce in return for experience, cash and horseshoes. You will need to fill all slots on the ship for it to sail away immediately. If you are unable to fill the boat, it will remain in harbour for 6 hours before sailing. It returns after an absence of 6 hours.
Once you have visited one of the temporary farm events, i.e. The Island Farm or The Northern Lights Farm, the ship will offer 2 extra slots to fill before sailing. These are for fruits which are grown in the greenhouse from seeds bought with runes or shells from the event farm. Once you have visited one of these farms, you will always have to fill 6 slots on the ship.
Once you have visited one of the temporary farm events, i.e. The Island Farm or The Northern Lights Farm, the ship will offer 2 extra slots to fill before sailing. These are for fruits which are grown in the greenhouse from seeds bought with runes or shells from the event farm. Once you have visited one of these farms, you will always have to fill 6 slots on the ship.
The fruit sections have green arrows on either side. These are used to determine the amount of fruit you donate. There are 4 levels available and the ship defaults to the largest amount you have available. You can adjust it to a lower (more sensible) level quite easily.