In the garden, blue can have an almost mystical appeal. Think of an April sea of azure scilla (Scilla sibirica), a rich, purple-blue haze of ornamental sage (Salvia x superba) or clouds of lavender-blue catmint (Nepeta x faassenii). Used this way, blue has an ethereal effect, melting distant boundaries and suggesting shadows.

On the other hand, blue may be intense and startling: the translucent pure hue of the legendary Himalayan blue poppy (Meconopsis betonicifolia) or the equally blue, but more readily grown common morning glory (Ipomoea tricolor) and some of the more exotic selections like striped ‘Flying Saucers’. Other true blues include the gentians, lithospermum, some of the veronicas, annual cornflowers (Centaurea cyanus) and Chinese forget-me-nots (Cynoglossum amabile), and a few of the delphiniums. However, such clear blues are rare.

Many gardeners, famous and otherwise, have toiled to create pleasing, all-blue pictures. Curiously, such efforts often seem to fall short. Blue flower pigments (called delphinidins) reflect shorter light waves than those of red or yellow flowers, making blue plantings appear to recede in the distance. Therefore, blues are best planted and viewed up close.

As well, the colors embraced by the word “blue” do not always combine harmoniously. Better to separate the violet-blues from the clearer blues and make generous use of complementary contrasts in soft yellow and peach. One of gardening’s best know colorists, Louse Beebe Wilder, wrote in her 1918 classic, Color in My Garden: “It seems to me that from an aesthetic standpoint the segregation of blue flowers is a mistake. They, more than any others, need the flash of scarlet, the cloud of white, the drift of apricot or buff to kindle them into life and bring out their full quality.”

Here is a season’s worth of plant possibilities to lend a blue note to your garden.

A Paintbox of Blue, Purple and Lavender

Spring seems to offer the lion’s share of blue and purple. (For more on blue flowers at this time of year, read Spring Rhapsody in Blue.) The “little bulbs” – scilla, puschkinia, chionodoxa and muscari – sport various shades of blue and look lovely with daffodils and help to link the often strident red and yellows of early tulips. Other spring blues like forget-me-nots (Myosotis sylvatica), Virginia bluebells (Mertensia virginica), Siberian bugloss (Brunnera macrophylla), blue columbine (Aquilegia caerulea) and sparkling lavender-blue wild phlox (Phlox divaricata) are all enhanced by the fresh green of emerging foliage.

Late spring and early summer brings bearded iris in glistening lavender and purple, lilacs, false indigo (Baptisia australis), vivid veronica ‘Crater Lake Blue’ (V. austriaca teucrium), old-fashioned lupine, perennial cornflower (Centaurea montana), Siberian and bearded iris and peach-leaf bellflower (Campanula persicifolia).

Perennial geraniums (or cranesbills) such as ‘Johnson’s Blue’, deep violet G. x magnificum or purple ‘Rozanne’ make lovely companions to peonies and oriental poppies, while stately delphiniums in myriad shades of sky-blue, cobalt-blue, purple and lavender-blue add height to the garden. There’s even a wonderful little delphinium that’s the perfect size for for pots and the front of the border, Delphinium grandiflorum ‘Blue Butterfly’. At water’s edge grow slender Iris versicolor and Japanese iris, Iris ensata, with its stunning, large blossoms, often in rich purple.

There are vines with blue flowers too. With their long, racemes in late spring, both Japanese and Chinese wisteria can be considered part of the blue family, though the flowers of all the available cultivars have a good dose of purple. One of the best is Wisteria floribunda ‘Lawrence’. The clematis clan sports a number of blue-flowered species and hybrids, from lavender-blue Clematis alpina in spring to ‘Elsa Spath’, brilliant ‘Perle d’Azur’, rich purple ‘The President’ and, of course, easy ‘Jackmanii’.

Summer brings three more bellflowers, Campanula carpatica – the little Carpathian harebell with masses of light-purple flowers; the danesblood bellflower (C. glomerata) with its rich purple clusters; and tall milky bellflower (C. lactiflora) with airy, lavender-blue flowerheads. Rush-like foliage discloses the pretty purple flowers of the hybrid spiderwort Tradescantia x andersoniana. And no blue summer garden would be complete without at least one spiked veronica, perhaps one of the excellent, compact cultivars of Veronica spicata such as ‘Darwin Blue’ or ‘Goodness Grows’; exciting new Veronica. ‘Royal Candles’’ or old-fashioned Veronica longifolia. Then there’s balloonflower (Platycodon grandiflorum) with its namesake buds opening to lovely light purple flowers.

Two unusual-looking blue perennials for the summer garden are prickly sea holly (Eryngium amesthystinum) with steely-blue flower bracts and the tall globe thistle ‘Taplow Blue’ (Echinops humilus) with spiky, silver-blue flowerheads that are excellent for winter drying. And there’s blue pincushion flower (Scabiosa columbaria), either the old standard ‘Blue Butterfly’ or intense blue ‘Fama’.

Summer annuals with blue or purple flowers are plentiful: lavender and purple violas and pansies; lobelia; blue salvia (S. farinacea ‘Victoria’); purple browallia; sky-blue love-in-a-mist (Nigella damascena); intense Chinese forget-me-not (Cynoglossum amabile); borage (Borago officinalis); cupflower (Nierembergia); baby blue-eyes (Nemophila menziesii); ageratum ‘Blue Horizon’; and the graceful blue spikes of rocket larkspur (Delphinium ajacis).

The Blues of Late Summer and Autumn

Late summer sees the easily-grown shrub, bluebeard or blue mist bush (Caryopteris x clandonensis), with its steel-blue flower spikes so loved by bees. Another good late summer shrub is rose-of-Sharon (Hibiscus syriacus) which offers the pretty lavender-blue cultivar ‘Blue Bird’. And then there are the old-fashioned mophead blossoms of Hydrangea macrophylla, including ‘Nikko Blue’, ‘Seafoam’ and – for colder regions where mopheads have failed to thrive – ‘Endless Summer’. (Mophead hydrangeas need acidic soil to produce blue flowers; flowers grown in limey soil will be pink. To ensure blue flowers, amend your soil with a few handfuls of aluminum sulphate around the root area when you plant the shrub.)

Autumn features its own bounty of blue, especially the hauntingly lovely fall monkshood (Aconitum carmichaelii) with its intense azure-blue flower spikes that open slowly into November. And early fall is when Michaelmas daisies (Aster novi-belgii, A. novae-angliae and A. dumosus) strut their stuff, with masses of tiny daisies in blue, purple and lavender. Good asters include blue ‘Professor Kippenburg’, ‘Purple Dome’, ‘Royal Opal’, ‘Wood’s Purple’, ‘Wood’s Light Blue’ and, of course, the excellent native species New England aster, Aster novae-angliae with its small yellow-centered purple daisies so loved by bees and butterflies..

Blue-gray foliage plays an important role in the blue flower garden. Gertrude Jekyll certainly thought so when she wrote in 1908: “One never knew before how vividly bright ageratum could be, or lavender, or nepeta; even the grey-purple of echinops appears to have more color than one’s expectation. The purple of the clematis of the jackmanii class becomes piercingly brilliant, while the grey and glaucous foliage looks strangely cool and clear.”

Excellent foliage props include blue spruce, juniper, Russian olive, juniper, arctic willow (Salix purpurea), weeping pear (Pyrus salicifolia), blue oat grass (Helictrotrichon sempervirens), blue fescue (Festuca glauca) and the diverse selection of blue-toned hostas. The use of silver foliage nearby also intensifies blue flowers, as chartreuse foliage enhances rich purple flowers. For more on silver and blue-gray foliage, read Garden Silverware.

Adapted from a story that appeared originally in Canadian Gardening magazine

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