I agree in 100%
I am not a professional programmer.
I know a little bit about commodore basic and machine programming.
I am aware of the limitations of this computer.
had you picked EVERY single mint on the map?
Yes, all mint leaves.
maybe if the plants kept returning from time to time.
or better, every certain number of character steps. (possible problem with correct operation of the time clock in c64)
or an NPC item store
or get items in a winning fight
some simple and effective solution.