A Hydrangea Renaissance
by Sally Gregson

For too long hydrangeas have been ignored; passed over on the garden-centre shelves; dismissed as being problematic. Blue-flowered plants morphed into a liverish pink. They got too big too quickly. And to add to the confusion, hundreds of cultivars of Hydrangea macrophylla were sold under assumed names. It’s hardly surprising that gardeners lost interest.

But, at last, hydrangeas are enjoying a renaissance. Gardeners are looking again at their charms. And charms they have. In abundance. They are undoubtedly one of the best flowering shrubs for midsummer onwards. They are long-lived and easy to grow in soil that holds the moisture. And, if H. macrophylla is unsuitable for your garden, there are other species that bring a hit of colour when most other shrubs have long since faded from glory.

Hydrangeas come from opposite ends of the world. Some, H. quercifolia and H. arborescens are native to the Americas, while most of the remainder come from the Far East. In the wild the natural formation is that of the lacecap. The infertile florets around the edge are there to attract pollinating insects and butterflies to the discreet fertile flowers in the middle.

When European breeders selected out the entirely sterile mophead forms of H. macrophylla they started a craze that ran and ran, and finally ran out of steam in the sixties. However those varieties that remain popular are a fine legacy. Cultivars such as the pure white mophead H. macrophylla ‘Mme Emile Moullière’, or the rich red or purple lacecap, H. macrophylla ‘Rotschwanz’ would grace any modern garden.

However, for centuries Japanese gardeners have been selecting forms of H. serrata, a native of the wooded mountains of Honshu. These dainty little lacecaps possess a subtle charm and many continue flowering from July until their foliage reddens in the autumn. Some are traditional varieties. H. serrata ‘Beni Yama’, for instance, is identifiable from an ancient painted screen depicting an ‘ikebana’ flower arrangement. Many have charming, double flowerheads, such as H. serrata ‘Shishidanka’. And some are dwarf to put in a pot. Hydrangea serrata ‘Mount Aso’ with its ‘rainbow’ flowers makes a 60cm (2ft) mound.

Hydrangea paniculata also grows wild in the woods of Honshu among H. serrata. This more familiar species typically produces cream, pointed panicles of flower. Some of these comprise fertile flowers speckled with infertile florets, such as H. paniculata ‘Chantilly Lace’. While others are entirely sterile: H. paniculata ‘Phantom’ has huge heads that quickly fade raspberry pink.

The giants of the hydrangea world, H. aspera, come from the foothills of the Himalayas. Well grown, they have felted grey-green leaves the size of dinner-plates. And their lacecap flowers are similarly huge. The largest of this tribe are truly Himalayan in proportion, but the most popular, H. aspera ‘Villosa’ is more easily accommodated at around 2m (6 to 7ft) in a shady spot, sheltered from the wind.

The oak-leaved hydrangea (H. quercifolia) is equally spectacular. It too produces panicles of cream flowers in July. If the flowers are removed when they fade, they won’t detract from the grand finale: in autumn the leaves turn vivid scarlet. It prefers a warmer, sunnier place than most hydrangeas: a west-facing aspect is ideal.

Whether it’s a little H. serrata in a pot on the shady end of the terrace, a border of elegant H. paniculata or a magnificent H. aspera commanding everyone’s attention, hydrangeas bring colour, form and drama to the late summer garden.

Pink or Blue?

One of the main sources of confusion is the plant’s chameleon-like changes of flower colour.
In order for the flowers to be blue the plant needs to be able to absorb aluminium. This is chemically ‘locked up’ in alkaline soil, in much the same way as iron, so coloured flowers will be shades of red or pink.
On acid soils the aluminium can be absorbed and the flowers become blue.
White or cream flowers, however, age pink or red, never blue.