Trees
Trees in Croptopia closely mimic what can be found in vanilla.
Below is what a Dragon Fruit tree looks like.
If you want to replicate fruit leaves on your own trees, you will need a matching leaf block plus a sapling, and right clicking the sapling to the leaf block will turn it into a fruit crop.
The leaves must match the original tree, however. Right-clicking with a dragon fruit sapling on birch leaves will not work.