These true blue flowers bring a welcome cool and calm to gardens (and gardeners)

AT FIRST GLANCE, blue is everywhere in our Pacific Northwest corner of the natural world — bluebird skies, rivers, lakes and saltwater surround us. However, in the world of flowering plants, fewer than 10% produce truly blue blooms. And even then, most “blue” flowers are simply a variation on lavender. Please, don’t get me started on (dyed) blue carnations tarted up for a national holiday.

Visually receding in a landscape, blue flowers cultivate spaciousness and calm, as well as a sense of cooling relief when temperatures climb. The following blooms are true blue and promise to refresh the garden and hot, cranky gardeners alike. Most of these plants are annuals, but I’ve included related perennials, should you desire a more lasting relationship.

Bachelor button (Centaurea cyanus) is an easy-to-grow annual with cornflower-blue blooms and an upright growth habit that makes it easy to tuck into tight spaces among other plantings. Also known as cornflower, both the bloom and the color, the plant is considered a noxious weed by farmers when it shows up in grain fields — “corn” traditionally referred to all grains — contaminating the harvest.
• Mountain cornflower or knapweed (Centaurea montana) is a clumping perennial with showy blue blooms from late spring through summer. As far as I know, farmers are fine with knapweed.

Borage (Borago officinalis) blooms, which look like baby-blue shooting stars among a tangle of bristly stems and foliage, are nectar-rich and beloved by pollinators. Seedlings grow quickly in spring, bloom in early summer and readily reseed for future growing seasons. All parts of the plant have a pleasant cucumber flavor.

• Bugloss (Anchusa azurea) is a perennial plant in the same plant family, with delicate branching stems of azure blooms throughout summer. ‘Dropmore’ is a particularly tall variety with intense blue blooms.

Delphinium (Delphinium sp.) are undisputed garden glories with often-towering bloom spires in a variety of blues — “delphinium blue” is a color — as well as in shades of pink and pure white. Garden forms, including dwarf varieties, are categorized into several groups, and all require attentive garden care.
• Larkspur (Consolida regalis syn. Delphinium consolida) is a garden-worthy fuss-free annual with floriferous stalks clothed in single or double blooms and attractive lacy foliage.

Heavenly blue morning glory (Ipomoea tricolor ‘Heavenly Blue’) is my favorite summer blue. Although most gardeners have a complicated relationship with morning glory, this singular annual is a treasure and will not colonize the garden like nasty bindweed. Given warm conditions, twining vines with heart-shaped leaves quickly clamber up a string or wire trellis, unfurling a daily crop of sky-blue blooms — heavenly, indeed.

Perennial flax (Linum perenne) produces masses of sapphire blooms atop slender waving stems, providing a floral scrim for other plantings. The semi-evergreen plants thrive in hot, dry conditions and bloom all summer. I can’t think of a better planting for hellstrips and alleyways.
• Annual flax (Linum usitatissimum) has a similar upright growth habit and is often included in wildflower seed mixes and cultivated for its nutritious seed.

Mealycup sage (Salvia farinacea) is technically a perennial but is typically grown as an annual in our region. The popular and readily available variety ‘Victoria Blue’ is a compact grower that blooms prolifically up until frost with lavenderlike wands of deep ultramarine blooms.

• Anise sage (Salvia guaranitica) is considered a tender perennial but reliably overwinters in a protected location and well-drained soil. Emerging from a clump of aromatic foliage, tall, sturdy stems grow 3 to 4 feet tall, producing showy wands of dark, nearly navy, blooms in late summer. On the cultivar ‘Black and Blue’, the blooms emerge from striking black calyxes.