2020: Year of the Iris

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Every year, the National Garden Bureau, a non-profit organization promoting the pleasures of home gardening, selects one annual, one perennial, one edible plant, one shrub and one bulb to celebrate. It’s a great way to discover a new plant or to learn a bit more about a plant you may already be growing.

Let’s look at the perennial chosen for 2020, the iris.

Year of the Iris

Irises are among the easiest of perennials to grow from bulbs, roots or rhizomes. The genus includes some 250–300 species featuring showy flowers. In fact, the iris takes its name from the Greek word for a rainbow, which is also the name for the Greek goddess of the rainbow, Iris. A perfect name for flowers that bloom in a rainbow of colors!

Irises are native throughout the Northern Hemisphere, with most of the species being of Eurasian origin. 

Bearded iris ‘Concertina’ with 3 standards (upright) and 3 falls (curving downwards).

Each iris flower has two types of flower parts, the “standard” stands upright and includes 3 petals. The “falls” curve outwards and downwards and are made up of 3 sepals.

The three main types of garden iris are Bearded and Beardless, both with rhizomes, and Bulbous. Each has distinct features to complement your garden.

Plant Iris Depending on When You Want Them to Bloom…

  • Reticulate—Late winter/very early spring
  • Dwarf Bearded—Early to midspring
  • Tall Bearded—Mid to late spring
  • Siberian—Late spring to early summer
  • Dutch—Late spring to early summer
  • Japanese—Early summer
  • Louisiana—Early to midsummer
  • Reblooming Bearded—Midspring and again in late summer to early fall

Bearded Iris

On the bearded iris ‘Air of Mystery’, you can clearly see the bushy orange beard on the falls.

Bearded irises, including the common garden iris or German bearded iris (I. × germanica), are identified by thick, bushy “beards” on each of the falls (sepals) of the blossoms. These hair-like beards are fuzzy and stand up from the sepals.

The German bearded iris (I. × germanica) is a natural hybrid, derived from a long-ago cross between the pale purple-flowered Dalmatian iris (I. pallida) and the yellow-flowered Hungarian iris (I. variegata). It now comes in a huge range of colors and some 30,000 varieties. It’s hardy in USDA hardiness zones 3 to 10.

It has been crossed with other species, notably with the pygmy iris (I. pumila), giving rise to the great variety of modern dwarf and median bearded iris cultivars.

Bearded iris rhizomes. Photo: alabamaliving.co

Bearded irises are grown from a thick fleshy mostly underground stem called a “rhizome”. The rhizome feels like a tough potato in texture. These rhizomes should be planted in the ground during the fall months to give the roots time to become established before winter. When you buy a new iris by mail order, you’ll probably receive a rhizome with clipped roots and leaves. It can remain out of the ground for a week or two without serious harm, but the sooner it is planted, the better.

Plant your bearded iris in a sunny (6–8 hours) location with well-drained soil planted with the top of the rhizomes at the soil level or up to an inch (2.5 cm) below the surface of the ground. 

Bearded irises do best with an all-purpose fertilizer, applied once in early spring and once after blooming.

In about 2 or 3 years, a decrease in blooms usually indicates that it is time to divide your plants. Be sure to divide the plant by cutting the newer parts of the rhizome free from the old section and discard the older part.

Bearded irises are commonly divided into six groups depending on the size of the flower and the height of the plant.

  1. Miniature Dwarf Bearded
  2. Standard Dwarf
  3. Intermediate Bearded
  4. Border Bearded
  5. Miniature Tall Bearded
  6. Tall Bearded

Each one of these classifications have a different flowering time, height and habitat. 

Reblooming bearded iris ‘Peach Jam’.

Some bearded irises are “rebloomers”, blooming once more in the same growing season in the summer or fall. The number of blooms you will get later in the season varies by variety and local conditions. There are now reliable and attractive rebloomers available in the marketplace which will perform in most climates, but although they can’t be counted on in colder ones (USDA hardiness zones 3 to 5). You’ll probably see the term “reblooming iris” on the label.

Beardless Irises

The Siberian iris ‘Shakers Prayer’ has no beard.

Often used for naturalizing or perennial borders, beardless irises are an easy and beautiful addition whether in bloom or not.

Though beardless irises are often called “water irises” and many do grow in marshy conditions in the wild, most varieties do great in regular home gardens. They enjoy a full to partial sun location and a balanced fertilizer in the spring when the plants are a few inches high. Japanese Irises are especially heavy feeders and appreciate a second feeding of fertilizer before bloom time. During dry periods, mulch the roots to help retain moisture.

Japanese Iris ‘Picotee’

If you buy your beardless iris in a pot, it can be planted at any season. Just plant it at the same depth in the garden as it was in the pot. 

If you receive a rhizome by mail order, though, it will likely be shipped in the fall wrapped in damp paper and placed in a plastic bag. Immediately remove the rhizome and soak the roots in water overnight. These roots do not like to dry out, so plant immediately, at the latest about four weeks before the first hard freeze. Beardless rhizomes like to be planted at a depth of 1″ (2.5 cm) (2″/5 cm for Japanese iris).

Beardless irises can grow for many years in the same location. Japanese irises are the exception—they like to be divided every three years.

There are six main types of Beardless Iris.

Louisiana iris ‘Rhett’

The first four types are commonly grown in gardens, and they all bloom late spring and early summer. The fifth type, the Pacific Coast Native, is native to the western regions of the United States and is not as well known. The sixth is Other and includes many of the flag irises seen in the wild.

  1. Spuria Iris (I. spuria), USDA zones 5 to 9
  2. Siberian Iris (I. sibirica), USDA zones 3 to 8
  3. Japanese Iris (I. ensata), USDA zones 4 to 9
  4. Louisiana Irises (I. fulvaI. brevicaulisI. nelsoniiI. hexagona, and I. giganticaerulea), USDA zones 5 to 9
  5. Pacific Coast Natives or Californicae (I. bracteataI. chrysophyllaI. douglasianaI. fernaldii, I. hartwegiiI. innominataI. macrosiphonI. munziiI. purdyiI. tenaxI. tenuissima and I. thompsonii), USDA zones 7 to 10
  6. Other beardless irises (includes yellow flag [I. pseudacorus], blue flag [I. versicolor], rabbitear iris [I. laevigata] and Virginia iris [I. virginica]), USDA zones 3, 4 or 5 to 9

Bulbous Irises

Dutch irises ‘Mount Everest’ and ‘Discovery’

These irises come from drier climates than the others and form a true bulb with a papery outer coating rather than a rhizome. They are generally sold as dry bulbs in the fall, along with tulips and narcissus.

They dry prefer conditions in the summer months, when they go fully dormant, losing their leaves.

There are two main types of bulbous irises.

  1. Dutch iris (I. × hollandica and related species)
  2. Reticulate irises (I. reticulata, I. danfordiae and others) 

Dutch irises are usually sold in the fall, but specially treated bulbs may be available in the spring. Plant the bulbs about 5″ (12 cm) deep with the pointed tip up.

These irises are a popular cut flowers, used by florists in seasonal flower designs. They flower in late spring to early summer and can be grown in sun or partial shade. The bulbs are hardy in USDA hardiness zones 6–9, surviving only sporadically in colder zones. However, even in the best of conditions, they tend to be short-lived, often blooming only once, and are therefore often used as annuals.

Dutch Irises look best when planted in groups. For a stunning show, plant about a dozen bulbs per square foot.

Reticulate iris ‘Katherine Hodgkin’

Reticulate irises are small plants with netted bulbs (that’s what reticulate means) that bloom in earliest spring, sometimes even late winter. They need full sun in spring and dry summer conditions. Most are hardy from zones 4 to 9 and can live for decades, often spreading. They are at their best in rock gardens and garden borders.

Even More Irises

There are many other irises to discover. Once you’ve tried a few of the more common ones described above, you’ll certainly want to get to know even more of the iris world in this, the Year of the Iris!

Unless otherwise noted, all photos are courtesy of the National Garden Bureau.

Black Flowers for a Goth Garden

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It seems particularly appropriate to write about black flowers at Halloween. Given the lugubrious nature of the fete, the most mournful of all flower colors, black, could certainly make a splash if you’re into turning your house into a haunted one. But you can actually have black flowers almost all year long if you know which ones to choose.

Most of us like our flowers bright: pinks, yellows, whites, lavenders, reds, etc. But not everyone. Some reactionary gardeners seem to prefer colors that get otherwise short shrift in the garden world … notably black. It’s not given to everyone to appreciate black flowers, but for those that do, they’re always a delight and they’re certainly original.

Of course, your love of black flowers may say something about you. Those who follow the Goth subculture and reject traditional societal values, for example, may be deep into black shades. The same can be said of some anarchists and artists. And if you’re in deep depression and want to stay there, black flowers may be just what the psychologist ordered. Also, growing counterculture black flowers could also be a way of finally interesting that rebellious grandchild in gardening!

Black Is Really Purple

Of course, it’s almost impossible to create a perfectly black flower. Most black flowers are actually a very dark shade of purple or red and will show up in those shades on bright, sunny days. However, many can look as dark as Hades on cloudy or overcast days or when contrasted with flowers in lighter shades. And some do darken as they age.

A Bouquet of Gloom

Here are a few black flowers whose gloom and doom color might suit more morbid readers:

Andean Silver-Leaf Sage
(Salvia discolor)

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Salvia discolor. Source: scott-zona, flickr

This is a large subtropical perennial with powdery gray stems and medium green leaves with a silvery underside. In late summer or early fall, it produces arching spikes of purple-black parrot’s beak flowers with silvery-green calyces that highlight the color. Only hardy to zone 9, it’s often grown as a tender perennial in colder climates: planted out in the summer and overwintered, after harsh pruning, indoors. Still, it needs a very long growing season, or the flower will be killed by frost before they open. Full sun and fairly dry conditions are best.

Black and Blue Sage
(Salvia guarantica ‘Black and Blue’)

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Salvia guarantica ‘Black and Blue’. Source: Proven Winners

This is another salvia with black flowers … except that it’s not really the flowers that are black, but rather the flower stem and calyces. It’s when the violet-blue flowers drop off that it becomes a “black flower.” The contrast between the bluish flower and the dark purple calyx is nevertheless quite attractive. It’s a lovely plant all round, starting to bloom early in the summer and continuing through the season, and a great hummingbird plant. It’s best treated as a tender perennial or annual where it isn’t hardy (zone 8 and above, zone 7 with protection). Salvia Bodacious ‘Rhythm and Blues’ is a newer, more compact variety. Full sun and well-drained soil.

Black Bat Flower
(Tacca chantrieri)

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Tacca chantrieri. Source: amazon.com

This tropical plant with leaves like a peace lily (Spathiphyllum) certainly does have impressive flowers! They’re composed of two dark “bat wings” (actually bracts) up to 1 foot (30 cm) across bearing nodding near-black flowers with long whiskers (also black in better cultivars) that hang down a good 2 feet (60 cm). Distinctly weird-looking! It’s often sold as a houseplant, but you’ll need really good humidity (i.e. greenhouse levels!) to keep it happy. Zone 11.

Black Bachelor’s Buttons
(Centaurea cyanus cultivars)

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Centaurea cyanus ‘Black Ball’. Source: mullerseeds.com

This is an heirloom variety of common bachelor’s buttons, dating back to 1942. The cultivars ‘Black Ball’ and ‘Black Magic’ are similar, if not identical. Bachelor’s buttons are fast-growing annuals that transplant poorly, so sow them where they are to grow, in full sun and any well-drained soil. It will self-sow where happy.

Black Bearded Iris
(Iris x germanica cultivars)

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Iris x germanica ‘Study in Black’. Source: bakker.com

There are more black bearded irises than I can count and they generally do look very black indeed. They’re hardy perennials and, if you can keep the iris borers off, bloom massively and stunningly just as spring is transitioning to summer. Consider ‘All Night Long’, ‘Before the Storm’, ‘Black is Black’, ‘Midnight Oil’, ‘Raven Girl’ and ‘Study in Black’ among others. Full sun or light shade in well-drained soil. Zone 3.

Black Calla
(Zantedeschia cultivars)

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Zantedsechia  ‘Odessa’. Source: easytogrowbulbs.com

There are actually several “black” callas, including  ‘Black Star’, ‘Edge of Night’ and ‘Odessa’. The extremely dark shade is all the most surprising in that callas (also called calla lilies, although they aren’t lily relatives) used to be renowned for their pure white flowers. But the big white blooms of yesteryear have largely been replaced by dwarf varieties with more narrowly tubular flowers in a wide range of colors, including pink, yellow, orange and dark purple … oops! I mean black! Grow callas as summer bulbs and bring them indoors in the fall in all but the warmest climates. Zone 8.

Black Columbine
(Aquilegia vulgaris and A. x hybrida cultivars)

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Aquilegai vulgaris ‘Black Barlow’. Source: http://www.longfield-gardens.com

There have been black (deep purple) columbines floating around forever in seed catalogues, usually with no name or just the words ‘Black’ or ‘Single Black’. ‘Black Barlow’ is a double one, but I must confess I dislike double columbines. They’re like a flower that tried to be a dahlia, but failed. Worse, they offer nothing to pollinating insects and hummingbirds, while single columbines are favorites with pollinators. Consider too the dark columbine (Aquilegia atrata), an easy-to-grow species with dark purple flowers, or A. viridiflora ‘Chocolate Soldier’, with very odd-looking, cup-shaped, purple brown flowers with a contrasting green calyx. All columbines are short-lived perennials that self-sow readily and thus keep hanging around years after you planted them. Plus they’re usually true to type unless there are other columbines in the neighorhood with which they can cross. They have their insect pests, but I suggest simply learning to ignore them. Perennial, zone 3.

Black Coral Pea
(Kennedia nigricans)

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Kennedia nigricans. Source: australianseed,com

I’ve seen this vigorous climber in tropical areas all over the world, although it’s originally from Australia. Apparently, it escapes from culture to become weed in mild, fairly arid climates where it climbs anything it can twist its greedy little wandering stems around. Often a machete is needed to hack your way through when it takes over brushy sites. Its parrot’s beak flowers with a yellow to ivory “tongue” are just about the blackest of any flower I have seen and they are borne quite abundantly spring through summer. Grow it from seed as a tender perennial or houseplant in the brightest light possible … and keep your machete handy! Zone 8 and above.

Black Dahlia
(Dahlia x pinnata cultivars)

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Dahlia x pinnata ‘Arabian Night’ . Source: jparkers.co.uk

There is a Black Dahlia novel that was turned into a Black Dahlia film, both based on a famous Hollywood murder case, but most so-called black dahlias, that is, flowers, are, to my eye at least, at best very deep red. Still, the very double ‘Arabian Night’ gets credit for being the blackest dahlia, although ‘Black Embers’, ‘Black Jack’, ‘Black Satin’ and ‘Karma Choc’, all double varieties, give it a run for the money.. I’d say ‘Black Orchid’, with single flowers bearing narrow twisted petals on, is just as dark and perhaps even darker. Plant dahlias of any color in the summer garden, then bring them indoors and store them dry in a cool, dry spot for the winter. That treatment would apply in all by the warmest climates. Zone 8.

Black Hellebore
(Helleborus nigra)

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H. x hybridus ‘Onyx Odessy’. Source: carolynsshadegardensdotcom.

This tough evergreen woodland perennial normally has deep purple flowers, but true black? Not to my eye, but some hybrid hellebores, like H. x hybridus ‘Black’, H. x h. ‘Black Diamond’, H. x h. ‘Onyx Odessy’ and H. x h. ‘Slate’, come pretty close. This is an extremely early bloomer, starting in mid-winter in many climates. For sun to shade in evenly moist soil. Zone 4.

Black Hollyhock
(Alcea rosea ‘Nigra’ and others)

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Alcea rosea ‘Nigra’. Source: etsystudio.com

The single black hollyhock (‘Nigra’) has been around for a long time: Thomas Jefferson, the third American president, even grew it on his estate, Monticello, in 1629. The flowers are very dark indeed, definitely looking black in many light situations. There are now similar cultivars, like ‘Black Beauty’, ‘Black Knight’ and ‘Black Watchman’, but they seem to vary little from good ol’ ‘Nigra’. In fact, I have a sneaking suspicion most if not all of them are just ‘Nigra’ with a new name. There are doubles, too, including  ‘Black Prince’ and ‘Double Black’. Again, that may well be the same plant with two different names. The fig-leaved or Antwerp hollyhock (A. ficifolia) likewise has black-flowered varieties including ’Jet Black’, ‘Black Cherry’ and, simply, ‘Black’. They’re reputed to be resistant to hollyhock rust, a disease that damages the foliage of the common hollyhock (A. rosea). Hollyhocks are either biennials or short-lived perennials, but they self-sow and can thus maintain themselves for decades. Great as a tall black flower for the back of the border in a fairly sunny spot. Zone 3.

Black Hoya
(Hoya ciliata)

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Hoya ciliata. Source: burbnursery.blogspot.ca

This is a fuzzy-leaved climber bearing star-shaped deep maroon to black flowers with a yellow crown in the center. They are said to smell like peanut butter! I mention “said to”, as I have killed this plant twice and have yet to see it bloom. This is definitely not your grandmother’s tough-as-nails wax plant (Hoya carnosa), but rather much more delicate, needing high humidity and careful watering at all times. Given its zone 10 rating, this is going to be a houseplant for anyone living outside the tropics.

Black Hyacinth
(Hyacinthus orientalis ‘Midnight Mystic’)

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Hyacinthus orientalis ‘Midnight Mystic’. Source: vanmeuwen.com

This is a fairly recent introduction (2007), but still, can be found if you look around a bit. And it’s now sold at regular prices: the first three bulbs sold for nearly $300,000 US, a record for a hyacinth! It’s by far the darkest hyacinth, yet perhaps its somber color is offset by its heady and delicious perfume. ‘Dark Dimension’, an even more recent hybrid, is very similar. Full sun to partial shade with good drainage. Zone 4.


Interested in black flowers? Read the second part: More Black Flowers for a Goth Garden!

When an Iris Blooms in Fall

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Iris x germanica ‘Best Bet’ blooming in October. Source:Moonik, Wikimedia Commons

This seems to have been a special fall for bearded irises in Northeastern North America. Several readers have written over the last few days (early October) to tell me that their irises are blooming for a second time. And these are irises that normally only bloom in late spring/early summer. My correspondants seemed especially concerned as to whether this off-season bloom would harm the plant.

Well, let’s answer that right off the bat: probably not. Plus it’s not as rare a phenomenon as you might think.

Plenty of Plants Rebloom Occasionally

There are quite a number of spring-flowering plants that occasionally rebloom in fall, including oriental poppies, primroses, perennial geraniums, lilacs, rhododendrons, azaleas, magnolias and iris. Usually this happens when the plant has undergone some kind of stress, such as a long period of drought or an exceptionally hot summer. However, sometimes there is no clear explanation. The plant simply starts to bloom outside of its normal season and no one knows why. And this out-of-season flowering is not really detrimental to the plant: it usually resumes its normal cycle the following year.

(Sometimes it’s best not to ask questions, but just to enjoy the result!)

Blooms in the fall usually do mean lighter bloom the following spring. That’s because the branches, stems or rhizomes that bloomed off-season won’t have time, at least in cold climates, to produce new flower buds for the upcoming spring. On the other hand, fall flowering is generally rather sparse and therefore it doesn’t necessarily have that much of a negative impact on the spring bloom to come.

Reblooming Iris

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Iris x germanica ‘Immortality’: probably the most popular reblooming iris. Photo: Iris Wiki

So much for regular bearded irises blooming in the fall, but there are also iris cultivars that naturally rebloom, that is to say, irises that bloom as usual in the spring, then a second time at the end of the season (August, September or October, depending on the local climate). They’re even offered in plant catalogs under the name reblooming irises.

In order to flower a second time, however, reblooming iris need the very best in growing conditions: full sun, good drainage, rich soil, regular fertilization (they prefer fertilizer not overly rich in nitrogen), little competition, etc. And they must be well established: rarely will they bloom a second time the first year.

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Reblooming Iris x germanica ‘Presby’s Crown Jewel’. Source: Iris Wiki

Also, although these irises are generally just as hardy as the other bearded irises, that is, to zone 3, they only tend to rebloom in regions with long summers. So it’s unlikely they’ll rebloom in zones 3 and 4, where summers are short, and rebloom is rare even in zone 5. It’s in zone 6 and warmer that this trait is the most reliable. But even in Zone 7, and despite the best care in the world, reblooming irises don’t reflower every year.

Reblooming is also unreliable in areas that with hot, humid summers, such as the US Gulf Coast, in spite of its mild climate. Hot, humid weather seems to stress reblooming irises … and not in the right way. In California, on the other hand, where the climate is both mild and on the arid side, some reblooming irises will bloom a third or even fourth time! They can even flower on and off throughout the year!

In My Own Garden

I’ve planted several reblooming irises over the years, but none have ever rebloomed. I do realize I live in USDA Zone 3 (AgCan zone 4), where experts claim the chances of reblooming are slim, but I’m an eternal optimist. Each fall I therefore eagerly scour my gardens for any sign of off-season bloom and probably will until my dying day. I figure I might as well grow reblooming irises as one-offs, as I still get abundant spring bloom and have a slight chance of flowers in the fall. After all, nothing lost, nothing gained!

Some Varieties to Try

Here are some reblooming iris that are available, at least from perennial growers … but you’ll find many more if you dig through specialist iris catalogs.

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Reblooming Iris x germanica ‘Champagne Elegance’. Source: David J. Stang, Wikimedia Commons

  1. I. x germanica ‘Again and Again’
  2. I. x germanica ‘Autumn Circus’
  3. I. x germanica ‘Autumn Echo’
  4. I. x germanica ‘Best Bet’
  5. I. x germanica ‘Café Blue’
  6. I. x germanica ‘Champagne Elegance’
  7. I. x germanica ‘Cordoba’
  8. I. x germanica ‘Double Click’
  9. I. x germanica ‘Double Your Fun’
  10. I. x germanica ‘Earl of Essex’
  11. I. x germanica ‘Eternal Bliss’
  12. I. x germanica ‘Feed Back’
  13. I. x germanica ‘Forever Blue’
  14. I. x germanica ‘Hemstitched’
  15. I. x germanica ‘Immortality’
  16. I. x germanica ‘Jennifer Rebecca’

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    Iris x germanica ‘Mariposa Skies’. Source: Iris Wiki

  17. I. x germanica ‘Mariposa Skies’
  18. I. x germanica ‘Misty Twilight’
  19. I. x germanica ‘Pink Attraction’
  20. I. x germanica ‘Presby’s Crown Jewel’
  21. I. x germanica ‘Pure as Gold’
  22. I. x germanica ‘Recurring Delight’
  23. I. x germanica ‘Speeding Again’
  24. I. x germanica ‘Stellar Lights’
  25. I. x germanica ‘Summer Olympics’
  26. I. x germanica ‘Thrice Blessed’
  27. I. x germanica ‘Witch of Endor’
  28. I. x germanica ‘Ziggy’

Other Reblooming Iris

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Reblooming Siberian iris ‘Ever Again’. Source: woottensplants.com

There are also reblooming irises in other categories, notably Siberian irises (I. sibirica) like ‘Ever Again’ and ‘Slightly Envious’, and Japanese irises (I. ensata) like ‘Purple Plus’ and ‘Triple Treat’, although they tend to bloom immediately after the first bloom or shortly thereafter, not in late summer or autumn.

Are you interested in reblooming irises? If so, you might want to join the Reblooming Iris Society.

Catalogs Offering Reblooming Irises

Here’s just a sample of many catalogs offering reblooming irises.

Canada

Breck’s Canada
Veseys

US

Breck’s
Hummingbird Gardens Iris Nursery
Schreiner’s Iris Gardens
White Flower Farm

Europe

Iris Cayeux
Kelways
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Seeking the True Blue Flower

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Blue is one of the rarest of floral colors; only black is more elusive. And that’s probably because of the complex chemistry involved in producing a blue pigment, because bees, butterflies and other pollinators actually find blue quite attractive and easily visit blue flowers. That means that, evolutionarily speaking, blue flowers should be a good choice for blooms and flowers ought to have evolved as readily in that direction as they did towards the pink, white and yellow flowers that are so common.

But it turns out blue is hard to produce. The blue in flowers comes from a pigment that normally gives red or purple hues: anthocyanin (from Greek meaning dark blue). Various forms of it as well as related chemicals give flowers their blue coloration. But most plants with reasonable quantities of this compound produce purple to red flowers instead. Why?

Well, that’s complicated. Suffice it to say that various molecules and metal ions have to be present and also the environment near the pigment cells has to be alkaline. Many plants with true-blue flowers (notably in the families Boraginaceae and Convolvulaceae) have pink buds that turn blue as their environment becomes more alkaline, but most anthocyanin-rich flowers have acid sap and therefore their flowers turn out purple or red. In flowers, blue is a co-pigementation: it needs the right conditions to express itself.

Blue Flowers Are Highly Desirable

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These orchids have been dyed blue. Photo: Tangopaso, Wikimedia Commons

Blue flowers are much appreciated in the florist industry, so much so that dyeing or spraying white flowers blue to make them more saleable is a common practice. Dyes are even injected into living plants to give a blue tint to their flowers. That’s the case of the blue orchids that are so often seen on the market these days. They are actually blue-tinted Phalaenopsis and the next time they bloom, the flowers will be white.

There are scientists all over the world working to introduce genes for blue coloration into popular cut flowers—roses, carnations, chrysanthemums, etc.—with, so far, only mitigated success.

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The Applause rose has “blue genes”, but looks dark lavender to me! Photo: Blue Rose Man, Wikimedia Commons

The efforts to create a blue rose (Rosa) by transferring genes from blue-flowering plants into hybrid tea roses have resulted in a so-called blue rose, Applause, launched by Suntory in 2009 … but in my opinion, it’s not really blue. It’s closer to lavender. Of course, that is an exciting new color for roses, but the true blue rose has yet to be created.

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To me, these “blue carnations” from the Mooncarnation series are violet. Photo: Pagemoral, Wikimedia Commons

The same played out for carnations (Dianthus caryophyllus). Scientists transferred genetic material from blue-flowered plants, plus deleted carnation genes that were hindering the coloration. The resulting “blue” carnations (all those that I know of belong to the series Mooncarnation) are actually different shades of purple and violet. Now, these are new colors for carnations, of course, but they certainly aren’t blue.

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Newly introduced, this “blue chrysanthemum” is not yet commercially available. It’s closer to blue than blue roses and blue carnations, but still, it doesn’t look quite blue to me.  Photo: Naonobu Noda/NARO

Very recently (July 26, 2017), scientists announced the creation of the first blue chrysanthemum (Chrysanthemum x morifolium). It was obtained by inserting genes from a bellflower (Campanula medium) and a blue pea (Clitoria ternatea) into a chrysanthemum. Again, these new mums are being touted as true blue, but I still see a lot of lavender in the flowers and would definitely not call them blue.

Note that these manipulations are all examples of genetic engineering. In other words, these plants are GMOs, a term that scares the s___ out of many people. That said, blue roses and blue carnations have been on the cut flower market for a decade now and I have yet to hear any outcry.

True Blue Blossoms

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Ipomoea tricolor ‘Heavenly Blue’: now that’s a blue flower! Photo: Russel E, Wikimedia Commons

Obviously, there are true blue flowers, and in fact they evolved all on their own and have been around for millions of years. I don’t think anyone will deny that a ‘Heavenly Blue’ morning glory (Ipomoea tricolor ‘Heavenly Blue’) is blue. Moreover, this cultivar was not developed in a laboratory nor is it even a hybrid. Instead, it’s a selection of the wild I. tricolor, a species with naturally blue flowers.

And that’s just one example among many … well, among “quite a few.” There are probably no more than a few hundred true-blue flowers among the some 400,000 plants on this planet.

How to define “blue”?

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Bluebells (here, Campanula cochleariifolia), are not really blue, but violet. Photo: Jerzy Opiola, Wikimedia Commons

In horticulture, there is a long tradition of claiming any flower even the slightest bit close to blue as being a blue flower. Above all, violet-blue flowers—definitely more violet than blue!—are universally called “blue” and violet is an abundant color in the floral world. I’ve always felt this was a case of wishful thinking: we’d like to have blue blooms, so we accept anything close to blue as being true blue.

This seems to be a worldwide phenomenon, by the way: in all the languages I know (4), purple flowers are regularly called blue. Linnaeus himself, the father of botany, named many violet-colored flowers coerulea, which means blue.

Also, I suspect the definition of blue varies from one individual to another. As I researched this article, I realized that I take a rather narrow view to “true blue”. I tend to apply that term to lighter blues (cyan, azure, sky blue, etc.), while to my eye, shades that could be considered blue (indigo, cobalt, etc.) are violet. I’m not sure everyone would agree!

Obviously, we could take the scientific definition of blue as a benchmark. Blue is caused by light rays ranging from 450 to 500 nanometers … but who has a device capable of measuring that?

True Blue Flowers

Here are some flowers that, in my eyes, are true blue. I’ll admit it’s a subjective choice, but—hey! —I am the one writing this article!

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Allium caeruleum. Photo: col&tasha, Flickr

  1. Allium caeruleum (blue globe onion) – bulb, zone 3
  2. Amsonia spp. (bluestar) – perennial, zone 4 to 6, according to species
  3. Anagallis arvensis (poor man’s weather-glass) – annual

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    Borago officinalis. Photo: Sten Porse, Wikimedia Commons

  4. Borago officinalis (borage) – annual herb
  5. Brunnera macrophylla (Siberian bugloss) – perennial, zone 3
  6. Centaurea cyanea (cornflower, bachelor’s button) – annual
  7. Ceratostigma plumbaginoides (leadwort) – perennial, zone 6
  8. Clitoria ternatea (blue pea) – tropical climber, annual
  9. Commelina communis (dayflower) – annual weed

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    Corydalis flexuosa. Photo: jardinierparesseux.com

  10. Corydalis flexuosa (blue corydalis) – perennial, zone 6
  11. Cynoglossum amabile (Chinese forget-me-not) – annual
  12. Eryngium spp. (sea holly) – perennial, zone 4
  13. Evolvulus x ‘Blue Daze’ (compact morning glory) – annual
  14. Hydrangea macrocarpa (blue hydrangea), blue in acid soils – shrub, zone 6
  15. Ipomoea tricolor ‘Heavenly Blue’ (morning glory)—annual climber
  16. Linum perenne (perennial flax)—perennial, zone 3
  17. Linum usitatissimum (common flax) – annual

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    Meconopsis betonicifolia. Photo: Andrew Curtis, Wikimedia Commons

  18. Meconopsis betonicifolia (blue poppy) – biennial or short-lived perennial, zone 3
  19. Mertensia spp. (Virginia bluebells and others) – perennial, zone 4
  20. Myosotis spp. (forget-me-not) – biennial, zone 3
  21. Oxypetalum caeruleum (tweedia) – annual
  22. Plumbago auriculata (blue plumbago) – tropical climber or houseplant

Flowers That Are Often Blue

The following plants come in a wider range of colors, including many violets and purples, but also some true blues. With these variable plants, if you want blue flowers, make sure you pick the right cultivar.

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Delphinium ‘Blue Fountains’: this mix from seed contains blue flowers, but also purple and white blooms. Photo: J.W. Jung Seed Co.

  1. Delphinium spp. (delphinium, larkspur) – perennial or annual, zone 2
  2. Gentiana spp. (gentian) – perennial, zone 2 to 6, according to species
  3. Eustoma grandiflorum (lisianthus) – annual
  4. Hyacinthus orientalis (hyacinth) – bulb, zone 4
  5. Iris x germanica (bearded iris, garden iris) – perennial, zone 3
  6. Lobelia erinus (edging lobelia) – annual
  7. Lupinus spp. (lupine) – annual or perennial, zone 3
  8. Muscari spp. (grape hyacinth) – bulb, zone 3
  9. Salvia guaranitica (blue anise sage) – annual in cold climates
  10. Salvia patens (gentian sage) – annual in cold climates
  11. Viola x wittrockiana (pensée) – biennial or short-lived perennial, zone 4

So-Called Blue Flowers

What follows is just a short list of plants many gardeners consider to have blue flowers, but that, personally, I find too close to violet to belong in that group. So if you’re planning a blue border, you might want to skip these.

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Ageratum houstonianum ‘Blue Hawaii’: a pretty shade of violet, but not blue. Photo: Swallowtail Garden Seeds

  1. Aconitum spp. (aconite, monkshood) – perennial, zone 3
  2. Agapanthus spp. (lily of the Nile) – summer bulb or perennial, zone 7
  3. Ageratum houstonianum (flossflower) – annual
  4. Anchusa spp. (bugloss) – biennial or perennial, zone 3
  5. Aquilegia coerulea (blue columbine) – perennial, zone 3
  6. Browallia spp. (browallia, amethyst flower) – annual
  7. Campanula spp. (bellflower) – biennial or perennial, zone 3
  8. Echinops spp. (globe thistle) – perennial, zone 3
  9. Geranium spp. (hardy geranium) – perennial, zones 2 to 9, by species
  10. Hyacinthoides non-scripta (bluebells) – bulb, zone 4
  11. Iris sibirica (Siberian iris) – perennial, zone 3
  12. Iris versicolor (larger blue flag iris) – perennial, zone 3
  13. Lobelia siphilitica (great blue lobelia) – perennial, zone 3
  14. Scilla siberica (Siberian squill) – bulb, zone 320170829A