Blue is one of those colors that feel exotic in the garden yet is actually very common. There are many shades of blue available in perennials that come in a range of hues and tints from pale blue to dark blue. You can have blue in the garden from early spring through late autumn without missing a moment, if you plan carefully. Here are some suggestions for blue-flowering perennials for your garden.
Blue Spring-Flowering Plants
In spring much of the garden’s color comes from spring-flowering bulbs. Many bulbs come in shades of blue. The earliest are squill, also known as the Star of Holland (Scilla siberica), a tiny bright blue flower that naturalizes quickly and can grow into a whole carpet of delicious cobalt blue in your lawn. These tiny flowers bloom before your grass starts to grow for the season, so they can be planted throughout your lawn and then the foliage will die back as the grass grows. Early Stardrift (Puschkinia libanotica) is another very early blooming flower with pale blue flowers that are star shaped. Blue flowering windflowers (Anemone blanda) in shades of powder blue and periwinkle are also a welcome sight in the early spring garden.
Blue Dutch hyacinths are not only beautiful but have a rich, bewitching fragrance. Blue varieties include ‘Blue Jacket’ (pale blue with purple inner stripe), ‘Delft Blue’ (solid periwinkle blue), ‘Blue Eyes’ (white with blue edges), and ‘Kronos’ (dark midnight blue).
English Bluebells are a familiar sight in a woodland garden, with their violet-blue bell-shaped flowers. Spanish bluebells are a type of hyacinth, with a cluster of nodding bells; they also come in shades of pink and blue. There are numerous types of bellflowers (Campanula) of different shapes and sizes, many of them in shades of pastel to vibrant violet blue.
Glory of the Snow (Chionodoxa forbesii) are tiny blue and white flowers that add a cheery pop of light blue in the landscape. Grape hyacinths (Muscaria) come in a range of blue colors from pale to dark, and two-toned. Muscari armeniacum ‘Valerie Finnis’ is a lovely pale periwinkle blue, while Muscari latifolium is cornflower blue and deep violet blue.
There are some blue spring-flowering phlox, including woodland phlox (Phlox divaricata) and creeping phlox (Phlox sublata). Varieties include ‘Blue Moon’ woodland phlox, and ‘Blue Carpet’ creeping phlox. Later in summer, there are tall phlox with blue flowers, including ‘Blue Flame’ (pale violet-blue), ‘Blue Boy’ (pale blue with red eyes), and Soft Touch Holly. Flowering around the same time are columbines (Aquilegia), with many blue varieties including ‘Blue Barlow’ (deep purple blue with many double petals) and ‘Bluebird’ (intense purple blue with white inner petals). Forget-me-nots (Myosotis) are small clumping plants with sprays.
of tiny sky-blue flowers with yellow centers. These bloom profusely for several weeks. They reseed readily in the garden but deadheading them before the seeds dry out helps slow them down a bit. If you see clumps popping up where you don’t want them, they are easy to pluck up and move.
Many blue irises bloom in spring, including Bearded Irises (Iris germanica) that come in miniature (early blooming), intermediate (mid-spring), and tall (late spring blooming) varieties. The early blue miniatures or dwarfs (Iris reticulata) include ‘Katharine Hodgkin’ (pale blue with yellow accents), ‘Alpine Lake’ (pale blue and white), ‘Raindance’ (pale periwinkle blue with white beards), and ‘Harmony’ (rich cobalt blue with yellow beards). Intermediate irises are usually between 12 to 24 inches tall. The blue varieties include ‘August Treat’ (very pale blue with blue beards and yellow accents), ‘Aqua Taj’ (medium blue with bronze beards), ‘Helicat’ (pale blue standards with dark purple falls and dark blue beards), and ‘I Feel Free’ (ruffled blue lavender petals with yellow beard). Siberian irises also come in shades of blue; these flower early, at the same time as intermediate bearded irises.
Other blue-flowering plants that bloom in spring include Amsonia (a small shrub), and lilac (Syringa vulgaris) which come in a variety of blue-toned colors, including ‘Wedgewood Blue,’ ‘Blue Skies’ and ‘Wonder Blue.’ Finally, the flower whose blue flowers are so famous that Crayola named one of its blue crayons after them:
cornflower. Also known as Bachelor buttons, cornflowers (Centaurea) have brilliant blue flowers the color of the sky at dusk. While the deep blue flowers are the most common, they also come in a range of other colors including pale blue, white, pink, lavender, and red. They are annuals that self-sow readily in the garden, making them essentially like perennials. The seeds may be collected to replant. The plants pop up quite early in spring, beginning their long bloom season in May.
Blue Summer-Flowering Plants
Summer brings a glorious assortment of blue-flowering perennials of all kinds. Certainly, one favorite is the blue-flowering hydrangea shrub (Hydrangea macrophylla). One of the best blue hydrangeas is ‘Nikko Blue’ which is very hardy and has reliable flowers with a long bloom period. Other blues include ‘Blue Jangles’ (a blue mophead style), ‘Magical Bluebells’ (periwinkle blue flowers with slightly scalloped petal edges), and ‘Enchantress’ (a vivid blue rebloomer). Blue-flowering hydrangeas need acidic soil for the truest blue color.
One enticing summer blue flower is the larkspur Delphinium elatum, which comes in a wide range of blue shades. Some of the taller hybrid varieties have fluffy blooms which can be a bit heavy and may need staking for support. Some of the bolder blue
varieties include ‘Buccaneer Blues’ (in shades of navy and cobalt) and ‘Magic Fountains’ (a range of pastel to medium blues and lavenders).
Virginia bluebells are a native flower that has clusters of charming light violet-blue, blue bell-shaped flowers that emerge from pink buds. The plants grow to around 2 feet tall. In some regions, they flower in late spring through early summer. They’re well-loved by many pollinators, especially butterflies.
Many blue-flowering perennial herbs make great additions to the flower garden. They include flowering catmint (Nepeta) which flowers profusely for weeks and attracts many pollinators, including honeybees and hummingbirds. Lavender (Lavendula) is another fragrant herb with pale blue flowers that is attractive to pollinators. Russian sage (Perovskia atriplicifolia) is a large bushy herb that bears long bracts of lavender blue flowers. These strongly scented flowers attract many pollinating insects. Borage (Borago officianalis) is also known as bugloss and starflower. It gets bright cheery blue star-shaped flowers in summer. These are edible and often eaten in salads or used to garnish summer dishes or drinks.
The Rose of Sharon (a type of perennial hibiscus) has several blue varieties that bloom for weeks in mid to late summer. These include ‘Blue Chiffon’ (with delicate double-formed petals of periwinkle blue), ‘Blue Bird’ (lavender blue single flowers with burgundy centers), and ‘Blue Satin’ (pale wisteria blue petals with a silvery sheen and burgundy centers).
There are a number of blue flowers that bloom later in the summer season. The blue mist spirea shrub (Caryopteris) is a beautiful addition to the late summer garden. The cultivars come in a variety of blue shades, including ‘Dark Knight’ (deep medium blue), ‘Longwood Blue’ (bluebird blue), and ‘Grande Blue’ (vivid periwinkle blue). These flower in late summer and attract many pollinating insects. Another late blue flower is the peacock plumbago (Ceratostigmoides), a hardy ground cover with bright blue flowers that have reddish-brown accents. Blue hardy ageratum (Eupatorium) produces many small, fuzzy powder blue flowers in late summer. The perennial variety grows to about 2 feet tall, while many gardeners also like the much smaller annual varieties. The perennial plants can be somewhat invasive, but their shallow small roots make them easy to control. Monkshood (Aconitum) is a tall late-blooming perennial that produces vivid midnight-blue flowers. It grows well in partial shade and looks good in the back of the garden as a colorful backdrop to shorter flowers.