If you want to create drama in your garden, by all means, pick all white flowers. People don’t usually crave intensity in a cottage garden, which is a care free collection of gregarious annuals and perennials suited to comfort the spirit rather than stir it up.
Most of the cottage garden staples do come in white however, and you certainly can get the look if you find it appealing. Here is a list of perennials that will carry the white flower theme through all the seasons.
For spring, hyacinths, peonies, lily of the valley, Solomon’s Seal, dame’s rocket, lilac, crocus, white bleeding heart, sweet woodruff, clematis.
For summer, lilies, daisies, white delphiniums, roses, yarrow, garden phlox, valerian, liatris, white bell flowers, hollyhocks, carnations, veronicas, catmints and hostas.
For fall, wind anemones, snakeroot, garden mums, white turtlehead and obedient plant.
For winter, snowberry, redosier dogwood, mistletoe and snowdrops.
These will ensure continuous bloom at least from spring to fall, and can be supplemented by a host of low maintenance annuals like petunias, impatiens, sweet alyssum, pansies, begonias, verbenas, Persian buttercups, sweet peas, angelonias, nicotianas, love-in-a-mist, larkspur, stock, cosmos, candituft, salvias, moss roses, spider flowers, snapdragons, which will fill the lulls between the perennial flowers with reliable all season bloom.

Author's Bio: 

Main Areas: Garden Writing; Sustainable Gardening; Homegrown Harvest
Published Books: “Terra Two”; “Generations”; "The Plant - A Steampunk Story"; "Letters to Lelia"; "Fair"; "Door Number Eight"; "A Year and A Day"; "Möbius' Code"; "Between Mirrors"
Career Focus: Author; Consummate Gardener;
Affiliation: All Year Garden; The Weekly Gardener; Francis Rosenfeld's Blog

I started blogging in 2010, to share the joy of growing all things green and the beauty of the garden through the seasons. Two garden blogs were born: allyeargarden.com and theweeklygardener.com, a periodical that followed it one year later. I wanted to assemble an informal compendium of the things I learned from my grandfather, wonderful books, educational websites, and my own experience, in the hope that other people might use it in their own gardening practice.