HYDRANGEAS

Hydrangeas are invaluable garden shrubs as they possess the ability to combine structure, colour and interest within one plant, filling their growing space with bountiful beauty. The Hydrangea genus are able to thrive in a variety of situations, but prefer a position in full sun or semi-shade, in fertile, moist, but well drained soil, fully to frost hardy. All hydrangeas are deciduous, and it's a welcome sign of spring when the new green leaves begin to appear. 

Some varieties maybe grown in the confines of large pots, which gives the advantage of being able to move them to prominent positions around the garden, once the flowers begin to open. The flowers last some considerable time, they look especially spectacular out on the patio. Larger growing species, some of which may become tree-like with age, are best suited to the back of the border, or to light woodland area.

Native to China, Japan, the Himalayas and both North and South America, Hydrangeas have been naturalised in compatible climates around the world. Their luxuriant dark green foliage offers a striking background for other border plants.

The genus hydrangea is divided into about eight subsections, which are further broken down into at least a dozen species and hundreds of cultivars -- there are so many different kinds of hydrangeas that it seems the exact number cannot be agreed upon. However the most common types of Hydrangeas seen in nurseries today belong to only five species: macrophylla, paniculata, quercifolia, anomala, and arborescens.

Flower colours range from white through to pink, red and purple to blue, but the blue flowers are only obtained on acid soil. It is possible to alter the colour of some species by their growing conditions. The blue or pink flower colour in these Hydrangeas is dependent on the amount of aluminium and iron available to the plant, more will result in blue, and less will give pink flowers.

The soil acidity determines the plant's ability to take up these two minerals. Many of the blue Hydrangeas need a pH of 6.5 or lower to achieve their best blue colour and pink varieties need a soil that is neutral (pH 7.0) or higher for their best pink colour.

Hydrangea varieties differ in their ability to utilize these chemicals, hence some tend to be pink, others blue. This is only a tendency and depending on soil pH any single variety can have a range of colours. Some have flowers which change as the flowering period progresses, they may appear pink at first, then begin to change colour with some petals even taking on tinges of green, then finally changing to blue.

Plant age also seems to affect flower colour and some varieties may take 2-3 seasons after planting to settle into the final stable colour. Adding aluminium sulphate to the soil prior to budding to produce blue flowers; or by liming or adding quantities of superphospate to the soil to produce pink ones may control the flower colours.

However it requires large quantities at frequent intervals to control the colour. Therefore if your soil conditions will not naturally maintain the desired colour, I believe it to be scarcely worth the effort, particularly as they are all so attractive in their own right.

PRUNING

With the exceptions of climbing hydrangeas such as Hydrangea anomala ssp. petiolaris and the shrubby H. arborescens and H. paniculata, which bloom on the current seasons growth, all other hydrangeas bloom on the previous year's wood and are essentially pruned in the same manner. Pruning in the late summer to early autumn must be avoided as it may encourage late growth that may not harden off for the winter rendering the shrub vulnerable for cold and frost damage.

It is often said that no pruning at all is better than wrong pruning and to some extent this is true. If hydrangeas are properly fed and get sufficient water, they will bloom if never pruned at all. True the shrub may become overgrown and a bit scraggly and not nearly as attractive as a properly tended shrub, producing fewer and smaller blooms but they will still produce flowers.

Proper pruning therefore is especially important with hydrangeas, for misguided actions can spell disaster, resulting in few if any flowers during the new season. While a young hydrangea needs little pruning beyond dead-heading, the more mature shrub may require the cutting out of dead stems, the removal of brown leaves, and the occasional errant vigorous stem that spoils the appearance of the shrub.

Even older hydrangeas may need a much more severe pruning. The best time to prune is during a mild break in late winter weather in February or March when the structure of the plant is quite visible and there is no chance of injury to new shoots.

Cut any damaged stem down to the base of the shrub if it shows no sign of rejuvenation. This severe pruning often results in a proliferation of new shoots from the base of the plant. Any woody stems particularly those in the centre of the shrub which do not have signs of new bud growth should be removed to allow sunlight and air currents to reach the centre of the plant.

The idea when pruning is to create a good framework of stems, which will ensure that even when not in flower the shrub still looks attractive and is able to produce healthy foliage. While the new stems will not bloom during the current season, they should put on a healthy display next season.

DEAD HEADING

The first form of pruning, especially for the H. macrophylla, or Lacecap hydrangea cultivars, is deadheading, or removal of spent blooms. There is some disagreement regarding the appropriate time to carry out this action for some believe that allowing the spent blooms to remain on the plant protects the buds of next year's flowers that are present along the existing stem during the winter. Some consider this a myth and take off the heads in late autumn.

Personally I prefer to retain the dried flower heads allowing them to remain until spring when they are removed. Deadheading is necessary as the spent blooms distract from the appearance of the current seasons flowers. Simply cut the spent blooms along with the flowering stalk, back to the uppermost pair of new buds, taking care not to damage any of the new green shoots.

CULTIVATION

All Hydrangeas like deep, fertile, well-drained soil in sun or semi-shade, they will require plenty of water in warm, dry weather. They prefer slightly acidic soil.  The pH of the soil will influence the color of the flowers. 

PROPAGATION

Generally speaking cuttings taken in the period from June to August easily root. The best cuttings are from the ends of non-flowering shoots with two or three pairs of leaves. Root them in light sandy compost in a shaded area. Another successful way to root the cuttings is to put them into a jar containing water, after several weeks the roots will have grown. Great care must be taken when placing them into compost so that the roots are not damaged.

DRYING HYDRANGEA BLOOMS

Hydrangea flowers make wonderful cut flowers for the home; they can also be dried so that their beauty is retained for a long period and they make wonderful floral arrangements. Flowers that are to be dried must be cut late in the season otherwise they fade and die before they have had the change to dry out.

The best species to dry are the "Mopheads" others are less successful. Choose the stems you wish to dry and simply stand them in a tall vase out of direct sunlight. Gradually they will begin to dry out, becoming papery but retaining most of their colours.

MOPHEADS/LACECAPS

There are two distinct Hydrangea forms, which are referred too as Mopheads and Lacecaps. Thy are both cultivars of the common hydrangea, H. macrophylla, rounded shrubs with oval, mid-to dark green, deciduous leaves. Their large, showy flowerheads are borne from mid-to late summer.

MOPHEADS

Hortensias (H.  macrophylla ) known as "Mop-heads," were named in honour of Hortense, the daughter of 18th century botanist Prince de Nassau. Mopheads feature large domed, dense heads resembling pom-poms, of mainly sterile flowers. Mopheads bloom in solid masses, their clusters often so heavy that they cause their stems to droop and bend especially when wet after rain.

LACECAP

Lacecap hydrangeas bear flat, open and rounded flowerheads with centres of fertile flowers surrounded by outer rings of sterile flowers.

Their centre flowers are small and inconspicuous, however thee outer rings of their sterile flowers are larger and quite striking. The name Lacecap is apt because the structure of these flowers are reminiscent of the cap edged with an outer frill worn by ladies during the Georgian period!

CONICAL HEADS

There is another flower head type similar to the Mophead but unlike those domed heads the blooms are somewhat longer with narrow, conical panicles. The flowers may be either white or cream, often taking on tinges of pink or green.

Many of my own favourite hydrangeas come from the paniculata group, and bear the conical type heads. 'Brussels Lace', 'Floribunda' and 'Unique'. Cultivars from paniculata are fast growing, upright with flowers appearing during late summer and early autumn. Flowers are mostly creamy-white, though some like 'Floribunda' become pink-tinged as they age.

Another beautiful white flowing Hydrangea that makes a spectacular show and one I would not be without is the gorgeous 'Grandiflora' belonging to the group Arborescens, This is an upright shrub with large, dense, rounded heads of creamy-white flowers.

H.anomola ssp.petiolaris, the most familiar of the climbing hydrangeas, requires little pruning at all. Once it is established it is self-supporting and quite independent. The only pruning necessary is that to confine the plant within its designated space.

Mature plants of H. anomola spp. petiolaris can climb to 75 ft. Removing dead flower heads close to the main stems promotes future blooms.

Evergreen Climbing Hydranges

The two evergreen climbing hydrangeas, H. seemanii and H. serratifolia require a sheltered position. After a slow start, the growth of these plants increases in vigour, but normally require little is any pruning. Prune only to confine them to their designated area. Cut them back a bit if they are growing on a wall, to encourage them to fully clothe the wall without projecting too far out from the wall.