asparagus might work as a background plant with its lacy foliage and 5 foot height, but being interplanted with some perennials the foliage might overwhelm them.

Asparagus is a heavy feeder and will not grow well if there is a lot of competition nearby. You can have a few ferns in the background, but they do seem to expand the crown diameters after a few years. The ferns do survive all summer, but don't become ferns until about mid June or late.r

{{gwi:663367}}

my asparagus is hanging over the wall in font of the side door.
hope this gives you an idea of what it looks like.
RexAnne