The same thing about stopping a growth to alter the settings applies to birth as well. You can, for instance, be doing a growth, then stop it, click birth and see how things are. Change "ivy leaf size" to 2, biggest size, and click birth again to see how that would look. Changing "leaf probability" to .959 (some branches will have leaves near the center, less as it goes outward) and click birth again to test that. Then growth to resume growing. It's pretty nice.

If you get a white bunch of leaves in Ivy Generator, it might be b/c the program isn't finding it's own leaf png files in it's path. At least when I start the program from it's bin directory, it shows textured leaves. But when I make a shortcut so I can jump back and forth to my Bryce projects, it looses the path to it's own leaves.