Purple Hydrangeas

The blog recently received a very nice letter from Kathy, a gardener on Quadra Island. She has become interested in the purple mop head hydrangeas she sees in her area. Her question: Is the rich purple colour with large heads a particular variety?



Two of our most knowledgeable members agree hydrangea colour is the result of soil ph. As long as you get a coloured mop head type and give it a lot of water and  the soil is acidic  you will get the purple blue colour. White varieties will not change colour.

Masja Purple, gardenweb.com

Big leaf hydrangeas (Hydrangea macrophylla) are the only type of hydrangeas that can change color depending on the acidity of the soil. Blue flowers thrive in acidic soils with a pH below 6.0; the higher the pH, the more alkaline your soil and the pinker the flowers will get. Somewhere in between at ph5.7 to ph6.2 is where, if you are lucky, you will get purple, on the other hand you may get a bush with both pink and blue heads.

unknown variety, greenvalleygrowers.com

Test your soil with ph kit available at garden centres. Then adjust with lime to raise the ph or sulphur to lower it. If you are changing the colour of an existing plant do it in small increments, it may take several months to get the colour you desire. It is much easier to prepare the soil before planting.

A few hydrangea varieties will reliably produce purple blooms in acidic soil including ‘Merritt Supreme’ ‘Mathilda Gutges‘ and Royal Purple’ which is one of the deepest purple hydrangeas.

Mathilda Gutges, hydrangeafarm.com

Hydrangea bushes are easy to grow. All hydrangea varieties are best in part-shade but will tolerate full sun if the soil is kept on the moist side.  Plant them in well drained, rich, loamy soil. Amend with rich compost for best results. Hydrangeas should be kept moist in the growing season for the best flower production. Pruning, if needed, should be done in the winter or early spring. Most hydrangea varieties bloom on old wood, so avoid extensive pruning in the winter if you want more blooms. Otherwise, cut back hard when dormant in winter or early spring. Hydrangeas can be cut back close to the ground if they get too large. 

Royal Purple, mlpaysagiste.com

Have you had success in growing purple hydrangeas? Do you have any tips on how to do it? Do you grow any of the purple varieties listed above? Is another variety a favourite for this area? Would you share some cuttings? We would appreciate your advice, please answer on the blog by clicking on the comment box and following the instructions.

More info: www.thespruce.com, http://homeguides.sfgate.com