Thanks sybrix, paulsvoboda! I will definitely be revisiting my grass for further definition. I love that texture you linked - it's amazing!
For now, here is my Corkwood trunk. It is not a full 1024 height because I'm planning to fit something above it, and this particular tree is much shorter/stouter than the Cypress and won't be needing quite as much length. There are 3 256 x 256 sections, of which the top two are tileable, and the texture also tiles horizontally. Still working on the branches/roots and foliage; in the meantime, critique and comments welcome!
Here is my concept again:
p.s. This time I'm gonna set the model up with an attempt at 3pt. lighting. For jeffro x]