Agave wrote:
Under a mature crab apple tree (w/ deep shade) I've begun planting
Pachysandra. If I intersperse ferns among the Pachysandra, will the
ferns survive (regrow each Spring) once the Pachysandra has spread to
cover the bed area? If not, is there something else that I can plant
that will provide a different texture/form in the Pachysandra bed?

Yes, of course. Mature ferns shoot up a couple of feet or more,
depending on species, just on the energy they stored below ground. Of
course, enough mature ferns will form a canopy and shade ground covers
to the point where they no longer grow. My ostrich ferns have decimated
the variegated vinca, the pachysandra and the lamium, though the
original few lily of the valleys have taken advantage of the situation
and are now the effective ground cover there.