Why is part of the tree billboard is cut off?

I have trees imported from Blender distributed on the terrain. ![alt text][1] You can see some of the palms' billboard is cut. ![alt text][2] I've had trees at more extreme angles and further from the trees point of origin that did not have this problem. Hoping someone has a trick to fix this. [Link to similar question.][3] Thanks for reading. [1]: /storage/temp/13124-tfp_plam_billboard.png [2]: /storage/temp/13125-tfp_plam_billboard1.png [3]: http://answers.unity3d.com/questions/238811/terrain-billboards-cutting-off-artwork-for-custom.html