Link to the original post for the diagram:

Written out:

Oak + Birch = Willow 10% chance *

Oak + Spruce = Mundane Larch 15% chance

Oak + Silver lime = Cherry 10% chance

Oak + Silver lime = Willow 10% chance *

*With the help of MouseyPounds and through my own and other forum members experience we believe the trees have a requirement of being in a swamp or a damp humidity biome in order to get a willow sapling mutation*

Birch + Silver lime = Cherry 10% chance

Birch + Spruce = Mundane Larch 15% chance

Birch + Silver lime = Willow 10% chance

Spruce + Mundane Larch = Bull Pine 10% chance

Bull Pine + Mundane Larch = Sequoia 5% chance

Jungle + Silver lime = Teak 10% chance

Jungle + Teak = Kapok 10% chance

Teak + Silver lime = Balsa 10% chance

Teak + Balsa = Desert Acacia 10% chance

Teak + Kapok = Myrtle Ebony 10% chance

wenge I think maybe bred by combining balsa and desert acacia, but it has no arrow and I haven't been able to get a sapling yet so its unconfirmed

Wenge + Balsa = Baobob 10% chance

Kapok + Myrtle Ebony = Yellow Meranti 10% chance

Kapok + Yellow Meranti = Willow 10% chance

Cherry + Silver lime = Walnut 10% chance

Cherry + Walnut = Chestnut 10% chance

Walnut + Silver lime = Chestnut 10% chance

Tell me if I missed something.

The key I've found is to create gigantic forests of the tree combo you need and have pure bee farms cycling 24/7 scattered throughout the forest.