This week’s post is inspired by a question from a reader (who also happens to be a blues musician) wanting more of that elusive color in his garden. Blue is a short wave-length in the visible spectrum, and a relatively rare color in flowers. The various wave-lengths of light have profound impacts on human mood, alertness and sleep patterns. I suppose that helps to explain why color can be such an emotionally-laden subject. I am permanently disturbed by descriptions of lilacs, asters, violets, etc. as “blue,” when it is quite clear to me that they are violet, lavender, purple and sometimes mauve, for goodness sake!

(*BB King didn’t call the song "How Mauve Can You Get?")

Anyway, here’s a list of some garden flowers which I consider to be truly blue, arranged more or less in order of bloom from spring until fall. They are herbaceous perennials unless noted otherwise. All of them grow or have grown here at the Cleveland Botanical Garden.

Siberian squill (Scilla sibirica)

Valerie Finnis grape hyacinth (Muscari ‘Valerie Finnis’)

Siberian bugloss (Brunnera macrophylla)

Virginia bluebells (Mertensia virginica)

Georgia Blue Speedwell (Veronica peduncularis ‘Georgia Blue’)

Common bluestar (Amsonia tabernaemontana)

Bluestar (Amsonia hubrichtii)

Bluets (Houstonia caerulea)

Blue Flax (Linum perenne, sometimes shortlived)

Delphinium (Delphinium, also sometimes shortlived)

Forget-me-not (Myosotis sylvestris)

Borage (Borago officinalis, annual)

Larkspur (Consolida orientalis, annual)

Heavenly Blue Morning Glory (Ipomoea ‘Heavenly Blue’, annual)

Love-in-a-mist (Nigella sativa, annual)

Cupid’s dart (Catananche caerulea)

Cornflower (Centaurea cyanus, annual)

True plumbago (Plumbago auriculata, tender perennial)

Houndstongue (Cyanoglossum amabile, annual)

Trailing lobelia (Lobelia erinus, annual)

Mophead hydrangea (Hydrangea macrophylla ‘Nikko Blue’ and other cultivars, like ‘Compacta, Goliath, ‘Endless Summer’ will produce blue flowers if the soil pH is acidic enough (between 5 and 5.5) to make aluminum available to the plant. Adding aluminum sulfate to the soil will result in bluer flowers for these Hydrangea cultivars, but may lead to toxic buildup after awhile)

Plumbago (Ceratostigma plumbaginoides)

Blue sage (Salvia azurea var. grandiflora)

Black and blue sage (Salvia guaranitica, annual)

Monkshood (Aconitum napellum)

Closed gentian (Gentiana andrewsii)

Posted by Ann McCulloh