Jovibarba is an outstanding and attractive genus comprised of five species.   The first four are very similar in the way that they produce offsets and are collectively referred to as "rollers".  The offsets are borne on short, very fragile upright stolons.  When the stolons dry the offsetts easily become detached and "roll" away from the parent plant.  J. heuffelii (the 5th specie) has it's own listing.  The rollers are very hardy (Zone 4) are very tolerant of dry conditions.  Most of the rollers are somewhat green when growing rapidly, however, as temperatures cool down in the Autumn, the plants display fabulous colors from yellow, scarlet, to deep purple.   They make great accents for troughs or other containers with other succulent plants.