by Emma Murphy, Master Gardener
Columbines (Aquilegia spp) are lovely perennials. I have had them in my garden for many years, and they always offer a pop of colour in the late spring/early summer garden here in Lakefield, Ontario.
These easy care perennials come in a variety of colours, shapes and sizes – most are bi-coloured, ranging from pastel shades to vibrant hues. Columbines have distinctive five-petaled flowers with long backward-extending spurs as pouchlike extensions of the petals, containing nectar. Sepals and petals are brightly coloured. The leaflets of the compound leaves are usually rounded and notched.
In my garden I have both cultivars and straight species (native) columbines, but it was a query on our Master Gardener of Ontario’s Facebook page about someone’s columbines changing colour from year to year that caused me to go down the research rabbit hole to try and find an answer for them.
What Did I Find Out?
Well, apparently columbines really like to hybridize with other columbines. They really do. They are also sensitive to their soil conditions and a number of other factors.
There has been some fascinating research done at universities like UC Santa Barbara (here and here). In one study they used two columbine varieties – red columbines pollinated by hummingbirds, and white or yellow columbines pollinated by hawk moths. Apparently hummingbirds prefer medium length nectar spurs (the ‘tails’ on the columbines), while hawk moths prefer the relatively longer-spurred species.
The study also noted that columbines can change from blue to red, then white to yellow. According to the researchers, the colour shift from red to white or yellow in columbines has already happened at least five times in North America.
So Why Do They Change?
There are several reasons why columbines change colours:
- DNA mutation
- Natural selection
- Adaptive radiation
- Hybridization
- Changes in soil conditions
DNA Mutation
Based on the UC Santa Barbara findings, at least 34 genes produce different columbine flower colours. Because of the presence of various genes, there’s an increased likelihood that the colours will change simply due to gene mutation. It doesn’t happen because of creation of new genes, but just because of current gene mutation.
Natural Selection
In the studies and mentioned above, if most pollinators are hummingbirds, most of the columbine colours are red. However, when the population shifts and most of the pollinators become hawkmoths, there’s a potential for the colour to modify. The resulting blooms can be white or yellow.
Adaptive Mutation
Another concept explored in the study of the columbine colour changes is adaptive radiation, based on Charles Darwin’s Theory of Evolution, which assumes that living organisms change their structures to better adapt to the changes in their surroundings. For columbines, flowers develop new traits as a response to changes in their environment. In this case, the changes include the pollinators.
Research shows that columbine flowers are tailored to the tongues of their pollinators, which shows an example of how they evolve based on their environment.
Hybridization
Columbine colour change can also be due to cross-breeding, when male and female parts are pollinated. The goal? Combining the positive attributes of two species, changing the physical characteristics, resulting in a better yield and disease resistance, among others.
Hybridization can also occur non-deliberately – for example when we plant two columbine varieties near each other, this will often create colour changes from the original plants.
To prevent problem hybridization, especially with our native Eastern Red columbine (Aquilegia canadensis), the best thing you can do is plant the native species as far away from the cultivars as you – not foolproof but an important thing to consider. Or don’t have any cultivars on your property, but that doesn’t guarantee they will stay the same as pollinators move from garden to garden.
Changes in Soil Conditions
It’s common for columbine colours to shift because of slight changes in the soil’s pH, as well as the presence or absence of metal ions in the soil. A pH lower or higher than 6.0 to 6.5 can result in nutrients being unavailable, which in turn can affect colour.
Colour change in columbines is a fascinating phenomenon, as you can see from my “rabbit hole research”.
But here’s the bottom line – if you want to keep your native columbines from hybridizing with cultivars you have to keep them as far away from each other as possible. If you like the idea of them changing colours (for a variety of reasons) just sit back and enjoy!
MORE READING
Sudden evolutionary change in flowers (2022)
Biologists discover a gene critical to the development of columbines’ iconic spurs (2020)
Dramatic diversity of columbine flowers explained by a simple change in cell shape (2011)
The Peterborough & Area Master Gardeners 
This post is very timely to a situation I’m now having. We only have natives growing – and some have been collected as single self-seeded plants into a large grouping for maximum effect. I started with a deep purple variety and a very light pink. then magically, (ha) I’ve now got a lilac color – definitely lighter than the dark purple, and certainly distinctive from the light pink. I now prefer the light pink and the newer lilac version in this large grouping. So I’ve commenced to removing the deep purple. Guess this little experiment will be unfolding over the next few summers! As heavy self sowers, it will be a while until all the dark purple are gone. That’s if I can keep ahead of the dead-heading! Thanks for the post. 🙂
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I’ve been growing columbines myself for many years but mostly trying to increase the number of the wild native red ones (formosa). I also cultivated all the colors you mention but always eliminated the pale ones. The first time I ever wondered whether the colors can change was after I had dug up a very dark burgundy specimen in the ditch along a county road in western Washington and planted it in a pot. Well, the followig spring it came out dark blue. But since I had never heard of such a change I assumed there had to be a mix up and dismissed the possibilty of a color change. However, none of my plants were missing the following season and I had not had any burgundy color before. For more than thirty years now I’ve been cultivating and propagating (from seed) formosa along with a variety of other types. As I look out the window I see all the plants that last season were native red are now pale washed out colors.
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