Your soil type will dictate the colour of Hydrangeas

Hydrangeas and their changing colours

Hydrangeas have long been used inn ornamental gardens providing much needed colour during the late summer months, especially the blousy mophead types with their huge pompom heads.

Many are sold initially as house plants and are then planted out into the garden where they more often than not seem to morph miraculously into a plant with different coloured flowers.

I am frequently asked the names of many of the Hydrangeas I have growing here at Green Island as visitors look with envy at their unusual deep rich colours in shades of crimson, royal blues and regal purples.

The look of disbelief is amazing when I explain that the one growing in Isobel’s garden is called ‘Red Baron’ despite its flowers being purple and blue.

Similarly H.’Merveille Sanguine’ (which means “Bloody Marvellous” in French) with its deep crimson flowers appears here in Meg’s garden with deep purple flowers!

One of my other favourites is H.’Purple Prince’, which is sold as a deep rich mauve colour, but will quickly revert to pink if grown in alkaline conditions.

I religiously take cuttings from my most prized specimens each year and label accordingly, however growing them on in multi-purpose compost means that cuttings from what should have been a bright blue variety are flowering this year in all sorts of shades of pink through to lilac!

The reason for this transformation is due to the acidity of the soil. In alkaline soil Hydrangeas will flower pink and in acid soil they will be blue. (White blooms are not affected).

It is possible to increase the acidity of your soil by adding aluminium sulphate, or alternatively crushed egg shells, orange peel or coffee grounds.

If growing them in pots use a compost for acid loving plants if you want blue flowers.

It is often a good way to assess the ph of your soil without a scientific test kit.

Plant a blue hydrangea and see what colour the flowers are the following year.

It may also be that it was growing in acidic compost when you bought it, so it may not turn completely pink in one season, but just purple initially, then lilac and finally pink as the roots extend out more into your garden soil.

All the above can be seen growing and flowering at Green Island Gardens. For further information visit www.greenislandgardens.co.uk