Leaves/needles on branches are densely packed in the middle, but sparse at the ends.

Using the sapling add-on I am making pretty realistic-looking trees, but I have not been able to figure out how to place the particle system needles or leaves in a satisfactory way, they are always crowded at the mid-point of each branches length & almost missing from the ends. I managed to mostly counter the placing of the particles close to the tree trunk by weight painting the rest of the branches and assigning a vertex group so that no needles or leaves are placed there (I think I described that correctly), but found that if I put more than one tree made that way in the scene, only one has any needles or leaves while the other is empty branches. Short of trying to weight paint the branches with different weights the best I can, if that even helps, I have not found any way to place the needles or leaves evenly. Anyone know of a way to place the particles like I want?

And I know there must be a way to make a different vertex group for each tree so they render with their assigned particles, but have not figured that out either yet. Even if that is not the way to achieve what I am looking for with this project, I will need to know this for another project at some point anyway, so anyone have any tips?