A number of flowers, shrubs, and vines have blue blooms or bluish foliage. You can use blue flowers to create an entirely blue garden, which can be quite striking, or as blocks of accent color in a garden. When choosing blue flowers for your garden, you should go to see them in person, if possible, since shades of blue vary widely, and you may be surprised by the hues of some blooms. It is also a good idea to seek out plants which are hardy in your area of the world: Lily of the Nile, for example, is a lovely blue flower, but it needs warm weather to thrive.
A number of bulbs have blue blooms, or cultivars with blue blooms. Irises, hyacinths, Amaryllis, and bluebells are some examples of blue bulbs. It is also sometimes possible to find bluish-violet tulips, although truly blue tulips have yet to be bred. Some examples of annuals with blue flowers include: petunias, lobelias, Ageratum, Bachelor Buttons, Nigella, larkspur, blue-fringed daisies, cornflowers, lupins, Evolvulus, and Blue Poppies. Some of these plants come in a range of shades, so it is important to see out blue cultivars specifically. If you have a pond or pool, you can also use blue lotuses and various blue water lily cultivars.
The foundation of a garden is often its perennials, the plants which are present year-round. Blue annuals are quite diverse, including: Salvia, Campanula, Veronia, statice, delphiniums, violets, blue flax, Baptisia, Caryopteris, Russian sage, spiderwort, forget-me-nots, sea holly, Platycodon, leadwort, geraniums, asters, Amsonia, phlox, chicory, blue-eyed grass, and blue mistflowers. Some of these plants will behave as annuals, rather than perennials, in cooler climates where the winter weather may become too much.
Ground covers like blue star creeper, Ajuga, and periwinkle can provide a blanket of foliage and delicate blue, while vines such as clematis, wisteria, and blue morning glories can be trained on trellises and fences. Blue flowers also grow on shrubs such as lilacs, some hibiscus cultivars, Vitex, butterfly bushes, and hydrangeas.
All of these blue flowers have differing water, soil, and sun requirements. It is a good idea to group plants with similar requirements together, to promote healthy growth in the garden and to make garden maintenance easier. If you live in an extremely cold, hot, wet, or dry climate, you may have trouble growing some of these blue flowers, although most of them will thrive in temperate climates.