But I'm also dreaming of planting lots of colorful perennials that won't thrive elsewhere in the garden. Inspiration comes from every mixed perennial border you've ever seen, and more recently from this display at the National Arboretum last June:
Tell me if you can spot a color scheme here:
Echinacea - Just bought three 'Tomato Soup' - bright enough for you?? (No, this is not my photo, but when I bought them they were indeed this color.)
Larkspur
Achillea
Japanese anemones
Really tall things, like eupatoriums, or perhaps vines on a trellis or stakes
Lilies - Adrian Higgins' recent column provides lots of inspiration
Poppies
Roses
Salvias
Rudbeckia - maybe this one touted by WFF

Etc.
The first step is to lay out the bed and start mulching this fall. Then annuals next summer and planting in the fall of 2011.
