Starf

Starf is a type of Berry that can be planted in the Farm. It can be obtained by encountering a shiny Wandering Pokémon while at least 1 plot on the Farm is empty. To start encountering Wandering Pokémon you need at least 1 ripe berry on your farm.

Roseli Setup
You can fill your farm in the following way to have the best chance to obtain Starf berries without any additional berries. Note that the setup omits a 24th Roseli, as that would allow Custap berries to mutate, and omits a 23rd Roseli as that would allow Lansat Berries to mutate if Dialga has been caught. Purple squares indicate where mutations can occur.

Roseli + Lum Setup
You can fill your farm in the following way to have the best chance to obtain Starf berries. Purple squares indicate where mutations can occur.

Important Notes
If possible it is highly recommended to obtain at least 8 Passho berries, and if possible 4 Lum berries, prior to obtaining the Starf Berry mutation. Without any Passho berries surrounding the Starf plot, harvesting a Starf plant even with a rich mulch applied will only ever yield 1 Starf Berry. Furthermore, harvesting a single ripe Starf berry with the maximum yield modifier (surrounded by ripe Passho berries [8 spots] that are all bordered by at least one Lum berry, and with a rich mulch applied to the plot the Starf is on) will still only yield 10 harvested Starf berries. It is necessary to use at least a combination of Passho berries and Ripe Mulch to increase the total amount of Starf berries one has with the exception of finding additional Starf berries or using the Enigma berry.