Blue is all around us. It’s what our eyes distinguish when we see the sky and sea. It’s in every smoothie-lover’s favourite superfood, the blueberry. It’s even found in our eyes themselves (or, at least, some of us). The fact that it’s Pantone’s Colour of the Year 2020 is no surprise, as this calming, serene hue is the favourite shade of many countries, including the UK, the US, Germany, Malaysia and more.
But did you know that blue, as a pigment, is actually very rare in the natural world? Yes, I’ve mentioned blue fruits, and we know that certain birds and insects appear blue to our eyes. But that’s just it – blue is usually an ‘appearance’. A facade.
Blue in butterflies
Butterflies have microscopic, scale-like structures on the membranes of their wings which cause them to appear iridescent. According to asknature.org, ‘Rather than absorb and reflect certain light wavelengths as pigments and dyes do, these multi scale structures cause light that hits the surface of the wing to diffract and interfere.’ The shape and formation of these structures actually determines the colour that appears to the human eye.
So the blue in butterflies has nothing to do with pigment at all. The exception is the obrina olivewing butterfly – this is actually the only animal in the world that produces blue pigment.
Blue in birds
The bluebird isn’t the only bird exhibiting blue colourings. There are, in fact, dozens, including the blue jay, barn swallow, belted kingfisher and more. However, just like 99.9% of butterflies, these birds trick the eye into believing that they’re blue.
Birds’ feathers also use different structures to produce their blue appearance. If you look a the feather of a stellar jay, for example, under a microscope, you’ll see that the barbs (the little hair-like structures which stem from the central shaft) are sectioned by tiny beads, which are spaced in a way that filters out everything but blue light.
Blue in plants
You guessed it. Most blue plants and fruits aren’t really blue. And I’m not talking about those vivid supermarket flowers that have obviously been dyed. I’m talking about some of our favourite plants, like bluebells, hydrangeas and irises.
Blue plants and fruits often utilise a red pigment called anthocyanin, which causes the plants to appear red, purple, blue or black, depending on their pH. That’s why certain blue flowers appear to vary in shade.
Why are certain plants and fruits blue? In plants, the colour attracts a wide variety of pollinators, while in fruits, the colour attracts herbivors, aiding in seed dispersal. Research also suggests that anthocyanins protect plants and fruits against extreme temperatures, as well as combining with chlorophyll in leaves to deter herbivores that might be attracted to the green colouring.
Mr Plant Geek’s favourite blue flowers
Muscari – this little spring delight is perfect for creating a carpet of blue beneath trees and shrubs. It’s incredibly easy to grow, and will multiply over the years, perhaps a little bit more than you’d like it too!
Delphiniums – these are tall and elegant, and come in many different shades of blue. Cut them down after flowering to initiate a second flush, that’s one of gardenings best kept secrets!
Pansy Frizzle Sizzle – pansies are amazing, but have you ever seen one with ruffled petals? Part of the innovative “frizzle sizzle series, this is a deep ocean blue, perfect for cool season containers.
Echinops – The globe thistle, it’s an amazing Hardy perennial, which fits well into cottage garden borders. It will grow on most types of soil, and makes a handsome bushy plant, with these blue spheres all through the summer.
Cornflowers- Easy to grow blue and your colour, look no further than cornflowers. You simply throw and sow, scattering the seed where you want it to flower. Look out for “Blue Diadem”, that’s the very best shade of blue you can find.
Petunia Night Sky – this amazing Petunia has been flying off the garden centre shelves for a few seasons now. It was a chance finding in a crop of blue purple petunias, and is prized for the speckles in the centre! A summer must!
Plumbago – A Vining plant that enjoys a warm summer, I often find this looks a bit like a blue flowered climbing geranium, so until the breeders can make that I’ll settle for this next best thing.
Clitoria ternatea – perhaps one of the best blues in the natural world, this plant is often used as a natural dye. It’s actually easier to grow than you imagine, creating a vining plant that will give you these little blue flowers during the summer, often quite late, but worth the wait.
Hydrangea – The classic plant the Madonna is documented as hating! Hydrangeas have been grown for many years across Europe, and I one of the easiest and most adaptable shrubs. Having said that, they do like to be kept moist at all times. On an acid so, you can also experience the very best blue!
What’s your favourite blue flower or plant? Or fruit! Let me know in the comments section below.
Michael has been involved with gardening and plants since he was just five years old. He is a self-professed Plant Geek, and was listed in the Sunday Times top 20 most influential people in the gardening world, thanks to his plant hunter role at Thompson & Morgan.
Michael was responsible for new plant introductions such as the Egg and Chips plant and the FuchsiaBerry and keeps busy travelling the world in search of new plants as well as lecturing worldwide, including stints in Japan. He is very active on social media – so why not give him a follow at @mr_plantgeek or Facebook.