I was reading this site and thought maybe others here would be interested in taking a look.
At first, these appeared to just be tubes and content for image hoses, but then I read on and noticed they can also do shadow effect, art effect, textures, tiles, and other methods - 2D and 3D. There are also one that works only in Painter, and provides brushes and textures for real-time painting of trunks, limbs, defects, etc.
Most products are designed to use the special abilities of Painter, Paint Shop Pro, and Photo-Paint. There are a couple products for Photoshop, but they appear to be limited to realistic hand-paintings of trees that can be placed into your pictures with the help of premade alpha channel masks.
BTW, skimming the tutorials at the site is a good way to see how these work. http://www.gardenhose.com/