How does the pH of the soil affect the colour of the flower?

Please state how, give examples, and also state the hypothesis (the relationship between the two).





e.g. the ...... the pH of the soil, the ...... the colour of the flower.

How does the pH of the soil affect the colour of the flower?
As you know, some flowers come in different colours. In some, but not all, cases, this is because the petals contain chemicals which are natural indicators, and change colour according to the pH of the soil. Where it gets complicated is that there's no general rule that applies to the colour changes associated with all the different species of flowering plant. In the case of hydrangeas for instance, blue flowers grow in basic soil. Add something acidic like sulphur dust or superphosphate and they'll turn pink. Add wood ash or lime and they'll turn blue again. But in other flowers the results are quite different because the indicator chemicals are different. The same happens when you pickle vegetables. The acidic pickle changes the colours of different vegetables differently.