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Hydrangeas are an excellent choice for any south coast garden and can fit with most garden styles or garden themes. Whether you prefer a cottage garden, a tropical style or a woodland garden the hydrangea is the plant for you. Their versatility isn’t limited to just garden styles and themes, they vary in height and colour and can be found native across Asia, North America and South America. The most common hydrangea is the Hydrangea Macrophylla which can come in shades of blue, red, pink, light purple, or dark purple.

Many people are aware that you can manipulate the colour of your hydrangea through soil pH. Soil with a pH of 5.5 or lower will exhibit blue hydrangeas, a ph of 6.5 or more will show pink, and soil in between 5.5 and 6.5 will have purple hydrangeas.

When I decided to plant a low growing hedge of hydrangea in my own garden, I envisaged a beautiful sea of blue flowers leading up to the entrance of the house. I had taken cuttings from a blue parent plant and knew that my soil was slightly acidic. I owned a stunning azalea which was constantly flowering and very healthy, I knew that it thrived on acidic soil. I did not feel the need to conduct soil tests as I was confident they would remain blue. Unfortunately, late spring proved me wrong. They were all pink. What did I do wrong?

The one thing I forgot to take into consideration was their proximity to concrete along the walkway. Cement is incredibly alkaline, with a pH of 12 to 13. To put that in perspective water has a pH of 7, soapy water has a pH of 12 and bleach has a pH of 13. Remember that blue hydrangeas need to have a pH of 5.5 or lower (similar to that of tomato juice).

Over time I added grass clippings and coffee grinds to drop the soil pH. It is best to take a gradual approach when changing soil pH instead of rushing out and buying a bottle of quick fix solution to change your hydrangeas.

From now on I remember to check the proximity of plants to cement structures especially fresh concrete on new houses and decks.

Tradewinds South Coast is here to help with all your gardening needs in the Shoalhaven, Kiama, Shellharbour and Illawarra regions.

Have fun in the garden!

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