I've seen a few mods floating around that allow you to add new types of fruit trees to the game, but is it possible to add non-fruitbearing types, like the vanilla game's maple, pine, and oak trees? If so, what mod would I need to use? I'm assuming something like ContentPatcher or JsonAssets, but I'm really not sure.
You'll need some changes in the game code to add a non-fruit tree, which isn't possible with Content Patcher and not yet supported by Json Assets. The only want to do for now is with a new SMAPI mod.