I learned my colors in kindergarten. The sky is blue. Water is blue. My eyes are blue. They are not purple.

‘Blue Daze’ dwarf morning glory

‘Blue Daze’ dwarf morning glory won’t have you in a purple haze – it’s really a blue bloomer!

Photo Credit: Holly Chichester

‘Black and Blue’ salvia

Want butterflies? Try ‘Black and Blue’ salvia in your true-blue garden.

Photo Credit: Amy Dee Stephens

‘Aurora Blue’ delphinium

The blooms of ‘Aurora Blue’ delphinium resemble tiny, blue trumpets.

Photo Credit: Amy Dee Stephens

Bachelor buttons

Bachelor buttons are one of the few flowers found more commonly in blue than any other color.

Photo Credit: Amy Dee Stephens

‘Heavenly Blue’ morning glory

‘Heavenly Blue’ morning glory is a climbing vine – heavenly, don’t you think?

Photo Credit: Amy Dee Stephens

Azure allium

Azure alliums look like round, blue popsicles growing out of the flower bed.

Photo Credit: Amy Dee Stephens

Lobelia

If you’re not caught up in creating a true-blue flower garden, Lobelia offers a number of species that bloom in various shades of blue and purple.

Photo Credit: Amy Dee Stephens

So why in the gardening world are purple plants called blue?

After much pondering and research, here’s the best layman’s answer I can offer: It comes down to the three primary colors. The varying shades of plant colors are all rooted in red, yellow or blue. Since red and blue combine to create purple, plants with almost any blue (cool tones) are considered to be “in the blue range.” You get it now, right? (Of course, it’s rare to find pink flowers that are named red something-or-other, but that’s just how it works.) You can’t trust plants’ names to be accurate. But it certainly explains why a flower like Carpet Blue petunia looks suspiciously like the color of a certain purple dinosaur.

Putting the pesky color wheel aside, blue is my favorite flower color. Perhaps the most appealing thing about bright blue is that it’s not common in nature. Plants and animals in shades of blue are real standouts. Hence, our attraction to bluebirds, blueberries and blue blooms.

Someday, I’m going to have an entire garden bed dedicated to truly blue flowers – without a purple wannabe in sight. I’ve been gathering my plant wish list based on my own visual verification so that the color is just right. Based on my judgment of what’s blue and what’s purple, here’s my Top 10 list of strikingly true-blue flowers:

The Bluest of the Blues

  1. ‘Blue Daze’ dwarf morning glory (Evolvulus ‘Blue Daze’) eats up the heat! Unlike most morning glories, this plant doesn’t act as a vine and climb – it’s a low-spreading mound. The sky blue flowers only last a day, but the next morning, the silvery leaves are again host to dozens of new blooms. (USDA hardiness zones 13-15)
  2. ‘Black and Blue’ salvia (Salvia guaranitica ‘Black and Blue’) and gentian sage (Salvia patens) have tall stalks of cobalt blue flowers complemented by bright green leaves. The sepal, or base, of ‘Black and Blue’ flowers really looks black – although it’s actually a deep, dark purple if you look closely. (USDA hardiness zones 7-10)
  3. ‘Aurora Blue’ delphinium (Delphinium ‘Aurora Blue’) has lovely tall spires of flowers. Sometimes called larkspur, the plant’s blooms are so dense they occasionally require staking, but they’re worth it! This beauty adds a nice “cottage garden” feel to a garden, and it reseeds itself. (USDA hardiness zones 3-7)
  4. 4. ‘Blue Mirror’ delphinium (Delphinium ‘Blue Mirror’) and ‘Blue Elf’ delphinium (Delphinium ‘Blue Elf’) produce bright blue, single, airy blossoms with a spur – quite unlike the spikes of ‘Aurora Blue’. They stay low to the ground and can bloom for months. (USDA hardiness zones 3-8)
  5. ‘Blue Enchantment’ ground morning glory (Convolvulus tricolor ‘Blue Enchantment’) is a creeping ground vine with lovely flute-shaped flowers. The inside of the bloom is yellow, the middle is white, and the rim is a royal blue. So striking! (USDA hardiness zones 8-11)
  6. Bachelor buttons (Centaurea cyanus) are considered one of the truest blue flowers because their color is natural, not cultivated. It was once fashionable for men to wear this small annual in a jacket buttonhole as a boutonnière. The thistle-type blooms are called cornflowers in Europe, and it’s such a unique blue that Crayola® named a crayon “cornflower blue” after this hue! (AHS heat zones 1-7)
  7. False vervain (Stachytarpheta jamaicensis) is a tropical beauty that sends up tall spikes of satiny, blue flowers – and hummingbirds and butterflies love it! Vervain is also legendary for treating various medical conditions. (USDA hardiness zones 8-12)
  8. ‘Heavenly Blue’ morning glory (Ipomoea tricolor ‘Heavenly Blue’) puts out the most beautiful heavenly blue-fluted blooms. As the vine’s name suggests, it flowers in the morning. The bloom color can range from light blue to quite dark. These tropical vines are most often used as self-seeding annuals. (USDA hardiness zones 12-15)
  9. Laguna™ trailing dark blue edging lobelia (Lobelia erinus ‘Lobeto’) is a midnight blue that seems impossibly dark and rich. Although lobelia comes in many shades of blues and purples, Laguna’s color is almost volatile. In fact, certain lighting and flash photography can alter its appearance to deep purple, so it’s hard to distinguish in pictures. (USDA hardiness zones 8-11)
  10. Himalayan blue poppy (Meconopsis betonicifolia) produces lovely flowers with blues that range from an aquamarine to turquoise, depending on soil content. Originally from the Himalayas and Tibet, this unusual and expensive plant demands cool, moist summers. (USDA hardiness zones 6-8)

Are there other blue flowers? Certainly! If you like light blues, you’ll also enjoy woodland forget-me-nots (Myosotis sylvatica), blue flax (Linum perenne), bigleaf hydrangeas (Hydrangea macrophylla), azure allium (Allium caeruleum) and more. Many plants that normally flower in purple, white or pink will have a named cultivar with true-blue blossoms.

If you aren’t hung up on the blue/purple thing, plant every blue-named plant you can find, and enjoy your purpley-blue garden. (After all, purple is the new blue!) And if you’re still having trouble making the distinction, go find the nearest kindergartener. Trust me: Any small child can set you straight on which flower is really blue and which one is actually purple.