Top of the mops

Hydrangea the king of colour

WHEN it comes to summer colour, not much can beat the sight of a mass planting of mophead hydrangeas.

These spectacular shrubs are flowering now and will continue right through to the frosts with their giant, pom-pom-like flower heads.

Hydrangea macrophylla, commonly known as Hortensia, are chameleons of the plant world – they change colour according to soil type.

Those with blue or pink flowers tend to be dusky shabby chic shades of mauve if there is a hint of lime, or a clear pink or red in alkaline earth.

In neutral soils, blooms may be a mixture of colours on the same plant.

Only the white flowers of varieties such as Annabelle are colour-fast. To get the best blue flower colour you must grow a variety such as Blue Danube in acid or ericaceous soil.

It is not acidity itself that affects colour, it is the aluminium in the soil and that can be absorbed by the plant only under acid conditions.

This fact has given rise to the claim that if you bury rusty nails, a saw or razors around the roots, the flowers will turn blue.

You can avoid this dangerous practice if you give your plants annual doses of hydrangea colourant.

Hydrangeas like cool, moist, welldrained soil to prevent the big leaves wilting, so find them a sheltered spot that is ideally in dappled shade.

Buy plants in bloom for instant colour and when planting, dig a hole to the same depth as the container. Add Rootgrow, a friendly fungus that encourages root development.

For impact put several plants two to three metres apart as a backdrop for flowerbeds or to make a hedge. They can also be grown in big pots. Mopheads also make great cut flowers. If you pick them in late summer when petals have begun to age and turn interesting vintage shades of burgundy and pink they can be preserved for winter arrangements.

Hydrangeas do not require much pruning but if you need to reduce the size, prune stems down to the base when the weather is mild in late winter to encourage a bushy plant.

Subsequent new stems may not produce flowers for a couple of years.