In the pink

by Adam Pasco

Hydrangeas exhibit a chameleon-like characteristic, changing flower colour according to the type of soil they're growing in.

HydrangeasMy usually 'true blue' hydrangeas have been a disappointment this summer. Yes they have flowered superbly, but not in the colour I wanted! The colour coordinated borders have always enjoyed a wonderful blue contribution from these well established hydrangeas, but this year they are undoubtedly pink. 'Blue Wave' has always been so reliable, but now it's not living up to its name.

Hydrangeas exhibit a chameleon-like characteristic, changing flower colour according to the type of soil they're growing in. The same variety can grow with a deep pink flower when grown in a chalky or alkaline soil but be deep blue in an acid soil.

There used to be a wonderful demonstration of this in the grounds of Nottingham University, at Sutton Bonington, where I studied horticulture. The soil in about eight beds was chemically manipulated by adding lime to make it more alkaline or sulphur to make it more acid, and a hydrangea grown in each. As they came into bloom during July you could see the colour transition down the row changing from pink to blue...a clear illustration of the affect of pH on plants.

My garden soil must have got more alkaline, possibly through watering with 'hard' tap water during hot weather last summer, hence the pink flowers this year. I'll need to change the balance and make the surrounding soil slightly more acid to prevent my hydrangeas staying in the pink. Watering with a solution containing aluminium salts will also help, so I'm buying some Hydrangea Colourant to apply to the soil round each bush. (A thought: could this summer's heavy rain make a difference to next year's flower colour?).

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Gardeners' World Web User 12/12/2007 at 14:03

Your climbing hydrangea is probably Hydrangea anomala subsp. petiolaris, which only comes in white! No matter how you feed it you will not be able to change its colour. Do take a look at a relative called the Japanese Hydrangea Vine, Schizophragma hydrangeoides 'Roseum', as this has pink flowers. An image search on Google will show you.

Hydrangeas are hardy shrubs, but new shoots can be damaged by frost in early spring. Delay pruning until spring as the old stems provide some frost protection. Then keep a sheet of fleece handy to throw over it on cold nights if frost is forecast.

Gardeners' World Web User 06/08/2008 at 19:39

Why have my hydrangea failed to flower this year i have got two in tubs and three in my borders

Gardeners' World Web User 06/06/2009 at 08:37

I was watching the Chelsea Flower show and Alan Titchmarsh gave instructions on how you should prune hydrangea petiolaris. You apparently prune after flowering and in the spring, but there was some detail that he went into about how you do it that I missed. Can someone remember what he said?

Gardeners' World Web User 20/07/2009 at 15:11

I have recently bought a white hydrangea which was really white when I bought it - now the blooms are turning a strange green colour. I like the white colour and don't want it to change to pink or blue - what do I need to do

Gardeners' World Web User 06/09/2009 at 20:24

your hydrangea sounds like one that I have that is white turns to green and then to pink, it will return to white next year as it is the nature of the lovely beastie,hope you continue to enjoy!!!you have three for the price of one.

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