The genus Selaginella belongs to the fern allies.  These are not true ferns, but they are vascular plants and produce spores, and thereby are linked with ferns. This species, Selaginella willdenovii is noted for his iridescent blue color.  There is another blue fern, S. uncinata, which also is known by the color it keeps.  Both of these plants are known as Peacock ferns.  However, the main difference between the two is one of size.  S. willdenovii is a much larger species and tends to climb, and under favorable conditions, may become invasive.  S. uncinata is a rather small species, and is easily kept under control.  Many people like to use it has a ground cover in an undisturbed area.