Pink hydrangea in foreground, blue in background July 2021

Nature and Nurture: the Colours of Hydrangea

These are blooms of Hydrangea macrophylla normalis, otherwise known as lacecap hydrangea.

Blue lacecap hydrangea July 2021
Pink lacecap hydrangea, grown from cutting in pot July 2021

The pink one is a clone of the blue one, grown from a cutting. The difference is that the plant with blue flowers is growing in the natural soil in my garden (supplemented with compost, fertilizer, and lots of water), while the pink one lives in a pot. The soil in the pot is a blend of natural soil, compost, various supplements, and lime. It may have been left over from the mix I put together for tomato plants the year I potted up the hydrangea cutting. The key difference is lime. I add extra lime to tomato soil to avoid so-called blossom end rot in the tomatoes. It’s caused by calcium deficiency, hence the need for lime.

According to Wikipedia, “An acidic soil (pH below 7) will usually produce flower color closer to blue, whereas an alkaline soil (pH above 7) will produce flowers more pink. This is caused by a color change of the flower pigments in the presence of aluminum ions which can be taken up into hyperaccumulating plants.”

Blue lacecap hydrangea July 2021
Pink lacecap hydrangea July 2021

Either way, hydrangeas perk up the garden, which starts to look tired by July. The flowers last for weeks, and even retain “interest” into the winter (meaning they hang on in a discoloured state, which may be somewhat interesting). I admit I prefer the blue colour, which is why I go out of my way to supply water to the plant starting in June, because it would bloom poorly or not at all otherwise. But seeing the pink flowers on the potted cutting-grown plant (which bloomed for the first time this year) has been a nice demonstration of nature and nurture.

48 comments

  9. Loved your explanation of the colors. I love hydrangeas and they remind me of the old litmus paper we used to use in science class. I wonder if schools still use litmus paper.

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    1. Harsh! I make extra efforts to water mine (especially this year) to make sure it blooms. I’ve heard they won’t bloom if pruned too late. But hey–I guess it’s too late for yours. 😉 🙃

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    1. Aargh! Those deer. I know which plants they like and mostly manage to apply deer repellent in time. That works quite well here, especially now that it no longer rains in summer. My hydrangeas and are in the fenced back garden so inaccessible to the chomping herds.

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        1. I use a spray with the brand name Bobbex. The ingredients include eggs, wintergreen, and garlic. It does smell kind of gross, but that’s the point. It costs about $20 for a bottle. I go through almost two per season. Each application is effective for about 2 weeks, although that’s without any rain.

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  13. Pingback: Litmus Test – e-Quips

  14. I had no idea that the color is related to the soil. Amazing, Audrey. I should pay more attention to what my garden needs. My hydrangea croaked last year and it makes me wonder if I wasn’t feeding it appropriately. Yours are beautiful… Enjoy!

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  15. My mob cap hydrangea in the front garden was a lovely deep pink ( and a lot smaller ) when we moved in 17 years ago, now it is a mixture of lighter pink and blue. I preferred the original pink! The dried flowers make a rather good ‘gothic’ indoor dried flower arrangement.

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    1. Mine don’t hold together long enough to look good dried, probably because the shrub is growing close to a big maple, so it struggles for water. Maybe this year’s crop of flowers will do better. They can turn interesting shades of off-colours. “Gothic” describes them well.

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  16. So envious, Audrey. I did have a hydrangea once. It died. I don’t know if it was the soil, not enough water, too much water, or simply that Warrandyte is hard on plants, but I never tried again. Ditto the camellia and the azelia. I would love to have such beauties in my garden. 🙂

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      1. Yes, I think that’s what happened to mine too. The summers here can be brutal and the poor thing was trying to survive at a time when we had water restrictions too. Roses, however, seem to thrive so I have a lot of them.
        I fear we may all lose precious plants if climate change is allowed to continue. :/

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          1. Some succulents and cacti are absolutely beautiful, at least when they flower. Because we’re in a bushfire prone area, I’ve planted a lot of succulents around the house. They’re not as lovely as the cottage garden effect I originally wanted, but they are pretty. And very hardy.

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            1. That’s true–I’ve seen lovely cactus blooms in Saskatchewan, of all places–on the Canadian prairies, where winter temps can hit -40C and summer temps +40C. And there are prickly pear cacti here in BC too. I know there are a lot of succulents and desert shrubs too. Of course all those need full sun, not possible under my Norway maples. I will soldier on with the tough and decent-looking plants that do well here, even with increasingly dry summers.

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              1. Ah, shade trees do change things. Do you have a water tank? We had a really, really bad drought soon after I built this place and water for gardens was severely rationed so heaps of us, me included, put in water tanks to catch whatever rain hit the roof. They really helped keep my plants alive. One of the best investments I’ve ever made. These days it’s nice to know I have that extra water in case of bushfires too.

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              2. I wish I had a really big tank, but there’s not much extra space on a 50 x 120 foot suburban lot. And it might not even be legal. I’ve seen tanks on rural properties, though. Who knows–someday houses may be built with cisterns or water tanks as part of the structure. I think you folks are ahead of us in that aspect.

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              3. Hmm…you just reminded me that /before/ that really bad drought, water tanks were illegal in the metro area as well. Now, we’re encourage to put them in. I’ve seen water tanks that are kind of like very big ‘bladders’ and they go under the house. Or maybe you could sneak a small one in under just one downpipe. Ssshh. I won’t tell. 🙂

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