Perennial growing height is important. Taller plants for the back of the border include Lillies, Acanthus, Delphiniums, Lavatera (Tree Mallow), Echinops (Globe Thistle) and Red Hot Pokers. Hollyhocks and Foxgloves give a real cottage garden look to your b
The color of the flowers, the bloom time and the overall garden design are all a big part of this but, perhaps, the most important thing to consider is the amount of sun the garden plant needs. - My Cottage Garden
Attractive heads provide form and interest in the border. Eryngium planum (Sea Holly) via garden.ee: This herbaceous perennial thistle has branched silvery-blue stems and and numerous small blue conical flowerheads surrounded by spiky bracts.
[Wonderful combination of plants. I think I'm looking at foxglove, tall bearded iris, and purple violas. Looks like maybe lamb's ear in the bottom left corner--excellent color foil.] What a great looking garden