For smaller tree trunks, creating a tiling texture from a photo will work well enough if most cases (and generating a normal from that). If you are making a bigger tree that will be a focal point, zbrush or any sculpting software would be the best option.
You can also use alphas of other tree textures and combine them to create a new tree bark. Or maybe adjust brush parameters to sculpt from scratch. There's some videos out there doing that but then bark alphas are added. Though just like zac said, it all depends on whether the tree is a hero piece or filler. Might try all…