The rarest colour in the garden: blue flower pictures
Fewer than one flowering plant in ten can make a blue flower — which is exactly why we collect them. FlowerBlue is a gallery of cornflowers, bluebells, forget-me-nots, delphiniums, gentians and the legendary Himalayan blue poppy. Browse the pictures, learn each flower's name and meaning, and find out when it blooms.
Sky-blue phlox-like clusters that flower for months.
Three weeks of blue
When a whole wood turns blue
Every April, ancient woodlands across Britain flood with English bluebells — around half of the world's population grows on one island. The display lasts barely three weeks, the bulbs take five years to flower from seed, and a single careless footstep can crush leaves the plant needs to survive. It is the largest blue flower spectacle on earth, and the most fragile.
Because no plant on earth has a blue pigment. Every blue flower in this gallery is an optical trick built from a red-purple molecule, and the recipe is hard enough that most species never manage it.
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Of flowering plants
Out of roughly 280,000 flowering plant species, fewer than one in ten produce a flower we would call blue.
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Naturally blue roses
Roses, tulips and chrysanthemums simply lack the gene for the right pigment. Blue roses in a shop are dyed.
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Ingredients required
Delphinidin pigment, the right cell-sap pH and bound metal ions. Miss any one of them and the flower comes out pink or purple.
It starts with delphinidin
Delphinidin is an anthocyanin — the same family of pigments that colours red cabbage and blueberries. On its own it is reddish purple. It is named after the delphinium, one of the first blue flowers it was isolated from.
Chemistry, not paint
To look blue, the petal has to raise the pH of its cell sap and lock the pigment onto metal ions such as aluminium, magnesium or iron, often stacked with colourless co-pigment molecules. Cornflowers build a ring of fifteen molecules around a single metal atom.
The gardener's blue switch
Hydrangeas are the one flower you can retune at home. In acidic soil below about pH 5.5 the roots can take up aluminium and the flowers turn blue; in alkaline soil the same plant flowers pink.
Blue is made for bees
Bees see ultraviolet, blue and green rather than red, and they are strongly drawn to blue and violet. The species that solved the chemistry were rewarded with some of the most loyal pollinators in the meadow.
Flower guide
Types of blue flowers
Names, short facts and blooming seasons for the best-loved blue flowers, from woodland carpets to alpine rarities.
Cornflower
Centaurea cyanus
Once a weed of cornfields across Europe, now a conservation priority. Its blue comes from a pigment complex so precise it is still studied by chemists.
Summer
Annual
Pollinators
English Bluebell
Hyacinthoides non-scripta
A protected woodland bulb that flowers before the tree canopy closes. The stem arches to one side — the quickest way to tell it from the upright Spanish bluebell.
Spring
Woodland
Scented
Forget-me-not
Myosotis
The classic flower of remembrance and a symbol of enduring love. Buds open pink and turn blue as the sap chemistry shifts inside the petal.
Spring
Self-seeding
Damp soil
Blue Hydrangea
Hydrangea macrophylla
The colour is a soil test in flower form: acidic ground and free aluminium give blue, limey ground gives pink. The same shrub can show both at once.
Summer
Shrub
Acid soil
Delphinium
Delphinium elatum
The backbone of the blue border, reaching two metres in a good year. Delphinidin, the pigment behind almost every blue flower, is named after it.
Summer
Perennial
Needs staking
Alpine Gentian
Gentiana acaulis
A cushion plant of limestone alps whose trumpets are so saturated that "gentian blue" became a colour name in its own right.
Spring
Alpine
Sharp drainage
Morning Glory
Ipomoea tricolor
Each trumpet lasts a single morning. The cultivar 'Heavenly Blue' opens a clear sky blue at sunrise and drifts towards pink as the sap acidifies.
Summer
Climber
Fast growing
Himalayan Blue Poppy
Meconopsis betonicifolia
Brought back from Tibet in the 1920s and an instant sensation. It wants cool damp summers and acid soil, which is why it thrives in Scotland and sulks elsewhere.
Early summer
Rare
Cool climates
Symbolism
What do blue flowers mean?
Blue is the colour of distance — of sky, sea and horizon. Because it is so hard for a plant to produce, blue flowers have always carried meanings of longing, loyalty and things just out of reach.
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Calm & tranquillity
Blue lowers the temperature of a room and a border. It is the colour gardeners reach for when they want stillness.
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Loyalty & remembrance
The forget-me-not has stood for faithful love and memory since medieval Europe, and is worn today as a memorial flower.
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Longing & the unattainable
The blaue Blume — the blue flower of German Romanticism — became the emblem of yearning for something never quite reached.
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Trust & new starts
Blue is the traditional "something blue" of a wedding: fidelity, honesty and a calm beginning.
Blooming calendar
Blue flowers for every season
Blue peaks twice a year — once in the spring woods and once in the summer border. Here is when each flower shines.
Mar – May
Spring
English bluebells
Forget-me-nots
Grape hyacinths
Siberian squill
Blue irises
Texas bluebonnets
Jun – Aug
Summer
Cornflowers
Delphiniums
Blue hydrangeas
Morning glories
Love-in-a-mist
Chicory
Sep – Nov
Autumn
Cape plumbago
Blue asters
Autumn gentian
Blue salvia
Ceratostigma
Dec – Feb
Winter
Algerian iris
Glory-of-the-snow
Blue primroses
Rosemary flowers
Early grape hyacinths
Shades of blue
The blue flower colour palette
Blue flowers range from barely-there mist to an alpine blue so deep it looks painted. These six shades are sampled from the photos in the gallery.
Misty Blue#CBDCF7
Plumbago#9FC2EC
Cornflower#6C9BF5
Azure#2D6CDF
Gentian Blue#0B52D1
Delft Indigo#12327E
Questions
Blue flower FAQ
What are the most popular blue flowers?
The best known blue flowers are cornflowers, bluebells, forget-me-nots, blue hydrangeas, delphiniums, blue irises, morning glories, grape hyacinths, gentians and the Himalayan blue poppy. Together they cover almost every shade from pale mist blue to deep gentian blue.
Why are blue flowers so rare?
Plants have no blue pigment. Blue flowers are made indirectly from delphinidin, a red-purple anthocyanin that only looks blue when the petal cell sap is the right pH and the pigment is bound to metal ions such as aluminium or iron and to other co-pigment molecules. Getting all of those conditions right is difficult, so fewer than one in ten flowering plant species produce blue flowers.
Are there any true blue roses or tulips?
No. Roses, tulips and chrysanthemums lack the genes to make delphinidin, so no naturally blue variety exists. Florists' blue roses are dyed white roses, and the genetically engineered Suntory Applause rose is closer to lavender than to true blue.
Which blue flowers bloom in spring?
Bluebells, forget-me-nots, grape hyacinths, Siberian squill, blue irises, glory-of-the-snow and Texas bluebonnets are the main blue flowers of spring. Bluebell woods and squill carpets usually peak between late March and May.
How do you make hydrangeas turn blue?
Blue hydrangea flowers need acidic soil, roughly pH 5.5 or lower, and available aluminium. Gardeners keep the colour blue by adding aluminium sulphate and an acidic mulch such as pine needles. In alkaline soil the same plant produces pink flowers instead.
Can I use the blue flower photos on FlowerBlue?
The photos come from Wikimedia Commons under Creative Commons or public domain licences. You can reuse them as long as you follow each licence, which usually means crediting the photographer and linking the licence. Full credits are listed at the bottom of this page.
Keep a little blue in view
FlowerBlue is a quiet corner of the web for the hardest colour in the garden. Scroll back through the gallery, find the blue you like best, and go and look for it outside.
