So, without further ado, here is the (currently incomplete) list of Greatfruit Grove tree combinations:
Applecot: Scorchberrry + Bulba
Manilow: Scorchberry + Manilow (or get it for 5 Bulba seeds in the market)
Bulba: Bulba + Boygo (Or get it for 5 Boygo in the market)
Bulba: Bulba + Manilow
Scorchberry: Scorchberry + Applecot
Scorchberry: Plantelope + Applecot
Scorchberry: Scorchberry + Plantelope
Boygo: Manilow + Boygo
Boygo: Boygo + Scorchberry
Plantelope: Boygo + Bulbat
Plantelope: Boygo + Plantelope
Halleberry: Plantelope + Bulba
Screwberry: Cuble + Boygo
And this is it so far! If you have details on the other Greatfruit Grove combinations, please let us know in the comment section below as we do our best to update this guide and fill it with all the possible combinations!
UPDATE: I have also posted a Greatfruit Grove guide in case you need some extra help with the game!