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Cultural Notes – 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 is 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. Shelter from winds is recommended.
Most 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. Flower colours range from white through to pink, red and purple to blue, but the blue / purple flowers are only obtained on acid soil. It is possible to alter the colour of some species by their growing conditions. The blue or purple flower colour in these Hydrangeas is dependent on the amount of aluminium, sulphur 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 will help 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.

Hydrangea colour tips:

Always best to do a soil pH test in several areas first and then you know what your working with.

For Blues into Purples you need a low pH below 6.0 (Acidic soil or potting mix) lower the better for Purples.

For Pinks into Reds you need a mid-high pH  6.5 and above (Neutral to Alkaline), the higher the better for Reds.

Good tips for changing pH:

Use Sulphur for lowering, Lime for increasing.

Blues/purples require aluminium sulphate to be available as a nutrient (This is only available when pH is low).

Reds require good amounts of potassium to enhance the deep pink colours into red.

If you need, we supply the test kits here and also the Aluminium suplhate, sulphurs and potassiums.

White Hydrangeas. Colour variance notes: “Hydrangeas are highly variable, responding to a matrix of soil chemistry, fertilisers, light, meteorological conditions and localised variants. They are living things and respond to a number of factors, like humans do to nurture as well as nature. We use these books as references, especially the ones by Mallet and by Van Gelderen, the latter photographically demonstrates the variance between plants exactly the same cultivar but in different locations, as well as variances of the same plant over different seasons. In short, describing a Hydrangea as white for example is the best fit, most likely result, commonly accepted way to do so in the nursery industry, but there will be variances, and there are no guarantees. Most white Hydrangeas are only purely so for a while, getting washed / faint colourings as they age.” We recommend regular deadheading to promote fresh new white flowers.

CULTIVATION: All Hydrangeas like deep, fertile, well-drained soil in sun or semi-shade, they will require plenty of water in warm, dry weather.
PRUNUNG: 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 hydrangeasbloom 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 atall 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 andnot 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 weatherin July or August when the structure of the plant is quite visible andthere 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 healthyfoliage. While the new stems will not bloom duringthe 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 thecurrent 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.
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!
For specific information or advice please contact us at Brenlissa Nursery for expert help. WE WISH YOU MANY YEARS OF ENJOYMENT FROM YOUR NEW HYDRANGEAS!