Easiest thing may be to try and make it seamless (in the vertical sense) yourself. To do this.... load the jpg you used into a paint program, then get a mirror image of the jpg (mirrored about the bottom of the image - not the side). Then append this mirrored image to the bottom of the original un-mirrored jpg and use that as the basis of the new texture. This way, the combined image will have the same colouring at the top and bottom of the image, so no seams (running across the tree trunk) will appear. Hope that makes some sense.

Dreams are just nightmares on prozac...
Digital WasteLanD