I’m in the second season of growing various stone fruit trees four-to-a-hole in backyard orchard style. I’m pruning each group of four so that the four together form a single vase shape. But it’s not clear to me whether the optimal vase shape has essentially one layer of branches forming the vase, or would it be good/better to have two layers of branches, forming a kind of vase stacked on a vase, either with a very short central leader connecting the two, or with branches coming out at two different angles (e.g. 30° and 45° so that one layer is above the other layer). The reason I’m wondering about this is that, as I understand it, the branches should not be allow to get too dense, which means a fair amount of sunlight can pass between them, even when leafed out. Perhaps a second vase below the top vase could receive that sunlight, rather than having it fall to the ground, wasted.
A closely related question is whether it’s good/better to allow short branched to grow toward the center vase, as a way of thickening the walls of the vase. They would, of course, need to be pruned to be kept short, but I’m wondering if perhaps this is another way of improving efficiency (not wasting sunlight).
I’ve looked at lots of resources on pruning for vase shape, but nobody ever specifically mentions whether the walls of the vase are supposed to be just one branch thick. (I understand that, in practice, one never has complete control over the placement of the branches, but I’m trying to understand what the target is.)
Any advice would be greatly appreciated.