"Jack" wrote in message
...

My question is -- is it a good idea to have separate (but adjacent)
borders -- one for autumn and one for summer, in totally different
contrasting colours? Or is it better to incorporate the autumn plants in
with everything else?

A design rule of thumb is generally to design for one peak season, trying to
design for too many seasons interest results in falling between two stools.
Think of Victorian country house gardens - each area peaked in one season
only: Rose garden, separate from herbaceous borders separate from spring
garden.......

But once you know the rule - break it! Early summer seed heads already in
autumn colours work well with the bold reds, yellows and russets or Autumn
flowering perennials. Think too about the shapes of the remaining seed
heads/leaves from the summer flowering and how thy work with the autumn
flower shapes.

Design in 4-dimensions! Along the border, height of plant, depth from the
front and time!

pk