I have one heather (December Red) since 2006 and it continues to thrive. It blooms for me from Dec-Apr. I have others with later bloom periods, it would be good to mix it up a bit for longer bloom.
Another thought would be a pieris - I think there are lower varieties, some get pretty rangy. They bloom early (great for the bees) then keep up a show with their brilliant new growth into fall. Evergreen as well.
I'd also mix in some spring blooming bulbs just for a pop.
