The big blooms of mophead varieties are guaranteed to turn heads, says Adrienne Wild
For summer colour nothing will beat the sight of a mass planting of mophead hydrangeas. These spectacular shrubby plants, which flower from June right through to the frosts, have large, pompom-like flower heads, often as big as your hat!
Even bedding plants can’t compete with the neon blue and pink flowers, which are also well known for their ability to change colour due to the soil pH or acidity, which affects the availability of aluminium.
Those with blue or pink flowers tend to be blue in acid soil conditions, turn through dusky shades of mauve where there’s a hint of lime to a clear pink or red in alkaline conditions.
In neutral soils (pH 6-7), blooms may be a mix of colours on the same plant!
To get the best flower colour, you must therefore choose varieties that will perform as you want in your particular soil type. Alternatively, you might prefer to experiment with a hydrangea colourant. Start applications well before the flowers appear, and continue every two to three weeks until autumn to boost and stabilise the blue shades.
Only the white flowers are colour-fast, regardless of soil type.
In general, hydrangeas like cool, moist, well-drained soil to prevent the big leaves and huge flowers from wilting. You may find it necessary to give your plants a dose of a sequestered iron tonic to prevent chlorosis, a yellowing of the leaves, which happens if lime in the soil locks up the available iron.
When planting, dig a hole to the same depth as the container. Add Rootgrow, a beneficial fungus that prevents ‘soil sickness’, to encourage root development and help the plant to become established quickly.
Due to the size of the bloom, a sheltered location is best to avoid wind damage. As for aspect, they enjoy shade, but too much will prevent them from flowering. So aim to find them a spot that is bathed with sunshine in the early morning or late afternoon, or in the dappled shade beneath trees.
Hydrangeas are also a good choice for milder coastal regions, as they have good tolerance of salt-laden sea wind.
Plant them in large pots or half-barrels to decorate a sheltered patio. Or consider planting several to make an informal hedge.
Mopheads also make great cut flowers, and if you wait until late summer when the petals have begun to age and turn interesting shades of burgundy and pink, you can preserve them for winter displays. To do this, just arrange them in a vase, with or without water, and leave them to dry.
Hydrangea macrophylla produce flowers from the topmost bud of each stem, and if that is damaged in winter or if pruned at the wrong time, they will not flower. The golden rule of ‘if in doubt – don’t’ should therefore be applied when it comes to pruning.
You can cut out deadwood at any time of the year and trim off spent blooms. If, however, you want to reduce the size of the shrub, wait until the weather is mild in late winter or early spring, before cutting them back.
Be aware, though, that subsequent new stems will not necessarily bear flowers for a couple of years.