Well, the only way to do it that I know of, is the way I do it. Lattices. In a paint program, design the tree in several parts. Start with the roots that go out from the bottom into the grass. Make it at least a 500 by 500 grayscale, Be as detailed as you want. Remember how lattices work and design accordingly. Paint with gray on black, not white, and apply some gaussian blur to it after you've finished. Design the tree trunk, the branches, etc in this way. create a lattice, then go into the terrain editor, click new, set your resultion to at least 510, 1040 is better, click from picture and import your gray scales. Then do that one by one for each part of the tree and position everything in Bryce to put the tree together. Use lowering to bring the height of the lattices down until the branches and such look round. It's complex, it takes a long time, and positioning is a pain, but it gets really good results if you put the time into it, and with the right materials mapped to it, it will look great. As per my piece Wizard's Tree. As far as foliage, you're on your own there, but you might try amorphium if you have it, to make some unusual, uneven foliage shapes rather than spheres. The texture mapping there is the real catch. Bryce still doesn't have diddley as far as decent foliage textures, but if you play with it and use foliage sparsely, but spread out in a somewhat realistic manner, it can look pretty fair

Talent is God's gift to you. Using it is your gift to God.