not sure about the jostaberry, but it,s a member of the ribes family which have the old wood cut out at ground level, annually in may.

Actually, according to Wikipedia, it's a complex hybrid between a black currant (Ribes nigrum), a gooseberry (Ribes uva-crispa), and the wild gooseberry from the West Coast of North America (Ribes divaricatum). It apparently fruits similarly to a black currant, and should probably be pruned the same way. Big advantage, it is very disease resistant, including resistance to white pine blister rust, which might help some of the neighborhood trees!