As the dog days of August approach and other flowering shrubs give up the ghost those stalwarts of the late summer border, the hydrangeas, come into their own. The common hydrangea, H. macrophylla, has spawned a huge range of varieties that divide neatly into two main types, the lacecaps and the Hortensias, or more descriptively the mopheads. The latter, also known as florists hydangeas, were originally bred as pot plants and were the classic floral decoration for tarting up the podium at significant municipal events where their brassy flowers were only outdone by the chains and gongs of the mayor and other civic dignitaries. These were unsuitable for outdoor cultivation but numerous garden varieties are now available.
Whilst not being the most subtle of blooms they nonetheless have a bouncy, Barbara Windsor like vitality about them as they sprawl and bulge under the weight of their fleshy, deep green leaves and outrageously over the top “afro” flower heads. This “Carry on up the Border” quality combined with a colour range that tends to the day-glo makes them ideal for a bit of “in yer face” seaside jollity but not so suitable for low key, subtly nuanced schemes! Where subtlety and sophistication are required the lacecaps are a better bet as the impact of their flowerheads is softened by the combination of a central plate of fertile flowers surrounded by a ruff of the larger, infertile ray flowers, similar to the Viburnums. Finally, continuing their slightly fairground quality remember that both types have the chameleon like capacity to produce blue flowers on acid soils and pink ones on alkaline soils such as at West Dean Gardens. Don’t be fooled by names like “Blue Wave” if you live in the Downs because she’ll be pinker than a stick of Brighton rock!
Whilst enjoying the “full on” feel of the common hydrangea it has to be said that the more refined pleasures of the other species and their varieties are generally more companionable and easier to place in the garden. With similar flower power to a mophead but of a more understated nature H. arborescens “Annabelle” has a graceful, open habit that errs on the pendent as its stems are bent over by the weight of its large, spherical creamy-white flowers. This characteristic that lends it to spilling down a bank or casting its cloak over front of border plants that are past their best. Larger and stiffer, H. paniculata is vigorous, spreading to upright, and bears large conical panicles of creamy white flowers that become tinged with pink as they age. “Praecox” flowers early in June, and is very informal and pretty but the most popular variety is “Grandiflora” which has massive flowerheads of mainly sterile flowers in September, a real late season blast! Slightly earlier and a little less over the top by dint of its mix of sterile and ray florets H. paniculata “Floribunda” is a more understated choice. Even more subdued is the N. American H. quercifolia, the oak-leaved hydrangea. Here it is the foliage that is the major attraction, like oak leaves on testosterone they are a cool soft green, colouring rich tones in the autumn, the pyramidal cream turning purplish flowers are pretty good to! H. aspera subsp. sargentiana is another strikingly foliaged beast. Here the leaves are very bristly and very large, up to 25cm, and evenly but fairly sparsely distributed over the stiffly upright framework of stems creating a dramatically sculptural effect when well grown. Like most of the hydrangeas the flattened terminal flower heads of blue-purple fertile flowers surrounded by white sterile ones also age well remaining on the plant in ghostly, sere form till next spring.
Closely related but with a different feel is what some consider to be the Queen of the tribe, H. aspera Villosa Group, previously known as H. villosa, aah the wonders of nomenclature! In August there is no lovelier shrub as its well shaped dome of downy foliage is smothered with lilac-blue flowers, combined with Pennisetum alopecurioides, Sedum spectabile and Rosa glauca its one of the highlights of the late summer garden. Finally we shouldn’t forget that there is also an extremely useful climbing member of the family, H. petiolaris. With the same self-clinging capacity as ivy and with similar vigour it is a wonderful, more unusual subject for cladding shaded walls. Its handsome dark green leaves which colour rich yellow in autumn plus its domed white flowers in June- July make it an invaluable climber, its pretty good at cladding old tree stumps or trunks as well.
Cultivation of Hydrangeas is pretty straightforward but a few basic points are worth noting. Firstly, the name Hydrangea comes from the Greek for water vessel a reference to the shape of the seed capsule, but it might better refer to the genus’s fearsome capacity to suck up water faster than a thirsty elephant! Be warned, a large specimen can hoover up more than 100 litres a day so a moist but well-drained, moderately fertile soil is essential. In areas of low rainfall and sharp drainage partial shade is preferred but in wetter, cloudier climes full sun can be tolerated, either way shelter from cold or drying winds is required. Pruning of H.quercifolia, H.aspera subsp. sargentiana and Villosa group and H. petiolaris is minimal consisting of the removal of spent flower heads in the spring as growth recommences. H. macrophylla and H. arborescens “Annabelle” are dealt with by removing all weak, spindly growth plus a proportion of the older less productive wood to the ground each spring and then tipping back any damaged branches by up to 30cm to a fat bud. H. paniculata can be pruned as H. quercifolia etc but to obtain really huge flower spikes it is best to establish a permanent framework 25 to 60cm high depending on its position in the border and cutting all growth back to the lowest pair of buds above this framework each spring.