For many ornamental gardeners, true blue — as seen in the Tibetan Blue Poppy called meconopsis — is the most prized flower color of all. And that’s probably because white flowers, and those in the yellow to red range of the spectrum, are so plentiful. Blue in general, offers a cooling, refreshing contrast, and true blue in particular, is adept at setting off the pinks and oranges.
Meconopsis would be stunning in any garden, but it is devilishly hard to grow and isn’t suited to our climate. However, if you have a very shady, humusy, moist spot where ferns grow, you might try the utterly charming Virginia Bluebells (Mertensia virginica), a perennial that blooms in spring and goes dormant by mid-summer. It’s good for a few seasons at least, before it realizes it’s not in Virginia anymore and peters out. Replant it by scattering seed in fall. You’ll be rewarded with a low-growing plant that hangs out clusters of pink buds that turn a dainty alice blue as the flowers open.
If you’re up for a challenge, various species and varieties of delphinium make a bold blue statement. Several varieties of the hybrid Delphinium x belladonna are blue, including ‘Bellamosa’ dark blue, ‘Cliveden Beauty’ pale blue, ‘Lamartine’ gentian blue, and ‘Sapphire,’ a delicate pale blue. The Chinese Delphinium (D. grandiflorum) is blue-violet, and blue pops up somewhat randomly in the Pacific Coast strains of this genus. I say “if you’re up for a challenge” because delphiniums grow flower spikes that need staking and plenty of water in the summer, so they take work. But they’re so darn beautiful, they’re worth it.
If you’re a rose lover, you are still awaiting the arrival of a true blue rose. Rose breeders have gotten close with lavender roses like ‘Angel Face’ but “close” is still a euphemism for “no cigar.”
Scientists have found that pollinators tend to avoid blue petunias, which puts them at a reproductive disadvantage. But the herb borage has blue flowers and you can’t keep honeybees and other pollinators away from it. If you want to attract pollinators to your vegetable garden, just sprinkle some borage seeds here and there.
One of the most familiar blue-flowered shrubs is the hydrangea. If your soil is sufficiently acid, say pH 5.0 to 6.0, your blooms will be blue. If your soil is neutral or alkaline, be prepared for pink hydrangeas, as that plant’s flower color is dependent on the soil’s pH. Soils in our region can be alkaline, so if you want blue hydrangeas, add gypsum or soil sulfur to lower the pH.
If you’ve lived here for more than 10 minutes, you’ll have seen the evergreen Lily of the Nile (Agapanthus africanus) carrying its big round blue heads of multiple florets in mid-summer. It works well in the back of a perennial border. And don’t forget the blue vines: the annual Morning Glory ‘Heavenly Blue’ and the perennials like Alpine Virgin’s Bower (Clematis alpina) ‘Pamela Jackman’; Large-Flowered Clematis (Clematis jackmanii), and other blue clematis varieties.
Use blue annuals to fill in around your perennials and shrubs. The beautiful Cornflower ‘Classic Fantastic’ (Centaurea cyanus) is probably the prettiest blue annual, challenged only by the Swan River Daisy (Brachyscome iberidifolia). Annual lobelias are striking as are the blue annual salvias. And for mounds of puffy blue flowers, think of Ageratum ‘Adriatic.’ Finally, the annual Love in a Mist (Nigella damascena) has light true blue flowers and will reseed itself all over the place, so you’ll only have to sow it once.