After weeks of cross-breeding trees, I think I may have just bred the "perfect" tree you're looking for. However I haven't bred every species of tree (still missing Willow, Desert Acacia and the trees that flow from there), so I don't know whether there are trees with better traits. But this is my current uber-tree:
- Species - Silver Lime - Apple Oak
- Saplings - Triple
- Matures - Fastest
- Height - Largest
- Girth - 1x1
- Yield - Normal
- Sappiness - Lower
- Supports - Nuts/Prunes/Pomes
- Fruits - Apple
This tree is huge, with more leaf blocks than any tree I've seen. It drops tons of Apples (which I put through a Squeezer for Apple Juice & Mulch for the Fermenter) and Saplings. And, because it's a Silver Lime, it's thinner than an Apple Oak, with leaf blocks extending only three blocks away from the trunk --- this means fewer nearby saplings are prevented from growing by the leaf blocks of a neighboring tree, which is important given the tight configuration of the multifarm.
I started by crossbreeding Silver Lime and Balsa trees, which gave me a Silver Lime tree with Balsa's Saplings (Triple) trait. Step two was to take this Silver Lime - Balsa hybrid and crossbreed it with a Sequoia, for Height (Largest). Finally, I crossbred this Silver Lime - Sequoia hybrid with a basic Apple Oak to get the above.
My cross-breeding setup was a cluster of six apiaries in the center of a circle of ten trees, five each of the two types I wanted to cross. I used Rural bees, as they combine a really good pollination trait ("Faster", better than Industrious) with being pretty easy to acquire.
Anyone have a better tree?