Hydrangea


(Species: Hydrangea - Family: Hydrangeaceae)

Hydrangea and its origins
Also known as Hortensia, Hydrangea comprises about 75 species of flowering plants native to southern and eastern Asia as well as North and South America.

Shrubs, trees and climbers, hydrangeas can be evergreen or deciduous, but the popular cultivated varieties are all deciduous.  

Seasonality: Hydrangea in flower
Hydrangeas bloom for a long period, producing large flowerheads of many small flowers from late spring onwards, and are popular hardy garden shrubs for both border and container.

Most garden forms derive from H macrophylla.  There are two key flower types.  Mopheads are large, almost spherical blooms; they are useful for informal hedges and are known for their inclination to change colour, depending on the soil's PH level.  Lacecaps have flatter, more open and graceful flowerheads. Their height and width is about 1.50m.

 

Other groups include the distinctive oak-leaved Hydrangea quercifolia, with conical white flowers, Hydrangea arborescens, notably Annabelle, with huge white drumstick blooms and the panicle-headed Paniculata Hydrangeas, such as pale mint-cream Limelight. There is also a climbing hydrangea, H petiolaris, which has small, white lacehead flowers in summer and can reach 15m in height.

How to plant: Hydrangea
As woodland understorey shrubs, hydrangeas are happiest in cool, semi-shade with moist, well-drained soil. Plant, and then mulch regularly, with plenty of organic matter such as garden compost or leafmould.   

The Hydrangea’s colour is not just down to its variety, but is also determined by the acidity level of the soil: the more alkaline the soil, the pinker the bloom; the more acidic, the bluer the bloom. White flowers remain the same. Keep blue flowers blue by planting in acidic soil or use special blueing compounds from the garden centre or specialist nurseries.

 

Water plentifully through dry spells; rainwater is ideal to water Hydrangeas, as hard tap water can turn blue flowers mauve or pink.

To keep in shape, remove dead stems and dead blooms at any time of the year. Dead blooms can be removed after flowering, but leaving them on mopheads over winter will provide frost protection for the new buds.

 

Hydrangeas flower on the previous year's growth and thus most pruning is carried out in late winter or early spring. Cut out the older stems to encourage fresh new growth. You can also renovate a neglected plant by cutting down all the stems, but the plant will not flower until the following year. Hydrangeas paniculata and arborescens benefit from hard pruning in spring.   

Propagation of Hydrangea
In summer, take semi-ripe (semi-hardwood) Hydrangea cuttings and root in a heated propagator or on a windowsill.  Cut the leaves in half horizontally to reduce transpiration.

Did you know?
Hydrangeas were introduced to the Azores Islands of Portugal, and grow in abundance there, especially on Faial, known as the 'blue island' because of the huge amount of blue Hydrangea which is found there