Fractals often exhibit the property of self similarity. This means that they resemble themselves at smaller scales. For instance, a tree branch often resembles the entire tree on a smaller scale. and a twig may resemble the branch as well. This way in which plants and other fractals exhibit self similarity makes for some fairly complex objects that are generated from quite simple formulas. For many fractal trees, plants, and ferns it is simply necessary to specify a couple of rotations/transformations for each iteration to create a quite realistic looking copy.
In many fractals, self similarity is apparent, but it does not look quite the same as the original object. It seems to have undergone a transformation but the transformation is not linear. Often the transformation is quadratic instead. These are called self squared
fractals.