Board Thread:News and Announcements/@comment-25404524-20161012035748/@comment-26863688-20161014014130

Started upgrading my Fruit Trees. Tree 1 and 2 needed 4 Vegidian Crystals and 100 coins apiece to level up 1. Tree 1 wanted 7 Vegidian Crystals and 400 coins for the next step, tree 2 wanted 1 Carved Vegidian and 100 coins. Then both want 4 Polished Frozium Crystals, 3 Vegidian Crystals and 500 coins.

So there appears to be no set schedule for upgrades.