One other method is using the totally free app l-system-4 a tree and branch maker that uses genetic blueprints to re-create the recursive forms found in nature. I've built dozens of trees this way. They can be huge, too. But are generally controllable to smaller polygon counts. You need to follow a few basic written steps to get your design off the ground, but once learned it's simple to get a good dxf model that can be multi-replicated in bryce. Laurence Lapre's site on the web. Hope this helps.