• Question: is it true that with some plants, the colour of their petals depends on the ph of the soil? and if so why?

    Asked by iluvgok to Eoin on 16 Mar 2011.
    • Photo: Eoin Lettice

      Eoin Lettice answered on 16 Mar 2011:

      Hi,
      Yes that’s absolutely true. The best example of this is in the Hydrangea plant (which lots of people have in their gardens).
      Depending on the pH of the soil, the flowers can be dark blue (low pH) or really bright purples and pinks (high pH). The presence of aluminium in the soil is what is actually determining the colour. But by changing pH you can alter how much of the aluminium is taken up by the plant roots.

      Hope this helps.
      Eoin!

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