Currently, Dark Patches in glitch are only useful for housing one type of tree: the Egg Plant. This makes the inclusion of a separate type of patch almost a waste, having it only exist for one tree type in the entire game. To mix it up a bit, I suggest a new dark patch specific tree, the Mushroom Tree.
Harvesting a Mushroom Tree, as the name implies, would provide 3, 6, or 12 mushrooms (depending on Gardening skill level) with the appropriate super harvest bonuses. This would remove the dependance on vendors for receiving mushrooms, while adding more variety to the game and making dark patches even more useful.