Hydrangea ~ Christmas Flowers

Hydrangeas have been popular garden plants for ages.  They are adaptable, highly decorative and long-flowering, and  they also have remarkable power of recovery, making them outstanding garden subjects.

‘Hydrangea’ is derived from Greek ‘hydro’ (water) and ‘angeion’ (vessel) referring to the shape of the seed capsule of the first species discovered.

H. lacecap Photo: Esther
Hydrangea ‘Lacecap’
Photo: Esther

Hydrangeas were first discovered in Japan where they are growing on the seashores.  This species comprised of a flat disc composed of tiny florets with stamens and pistils in the centre.  The smaller florets produced seed and pollen, the outer flowers are sterile. This species later became known as the ‘Lacecaps’.  A sport evolved from this species – it had a globose head composed of large sterile flowers.  Japanese growers soon realised that it had great commercial value and set out to cultivate this new variety, which was at that time unknown to the rest of the world.

The German plant collector, Engelbert Kaempfer (1651 – 1715) described the plants that he had seen or collected on his travels.  However it was Carl Peter Thunberg (1775-1828) who was responsible for the introduction of the hydrangeas  into Europe.

Hydrangea serrata & Hydrangea macrophylla Photo: Esther
Hydrangea serrata & Hydrangea macrophylla at Kew Wakehurst
Photo: Esther

Today there are many different species and varieties on the market, each very beautiful and different,  and they will all make a great contribution to any garden. The colours range from white, cream, palest blue through every exquisite shading to deepest purple, pale pink, glowing coral and deepest crimson. The fading colour of bronze, brown and pale green is equally exquisite.

Hydrange arborescens & Hydrangea 'Lacecap' at Kew Wakehurst. Photo: Esther
Hydrangea arborescens & Hydrangea ‘Lacecap’ at Kew Wakehurst.
Photo: Esther

In South Africa they flower around Christmas time, hence the name Christmas Flower or Christmas Roses. They are easily grown in most kinds of soil, they like a dappled shady position and need plenty of  water to thrive.

The most common species which are grown in South African gardens are Hydrangea macrophylla, Hydrangea arborescens, Hydrangea paniculata, Hydrangea quercifolia and Hydrangea serrata.

Hydrangea Walk at Kew Wakehurst Photo: Esther
Hydrangea Walk at Kew Wakehurst
Photo: Esther

The colour of hydrangea flowers is determined by the pH level of the soil. Acidic soil (pH of less than 5.5) will produce blue flowers, while alkaline soil (pH of higher than 5.5) produces pink blooms. You cannot change the colour of white hydrangeas.

Hydrangea arborescens at Hever Castlel Photo: Esther
Hydrangea arborescens at Hever Castle
Photo: Esther
  • For blue hydrangeas : Make soil more acidic by adding acidic peat to the soil. Feed plants with 25g of aluminium sulphate dissolved in 5 litres of water at two-weekly intervals from early spring onwards. Feed with Shake n Grow Blue Hydrangea Plant Food.
  • For pink hydrangeas : Make soil more alkaline by adding agricultural lime to the soil. Dust lime at the roots of the plant and water in well at two-weekly intervals from early spring onwards. Feed with Shake n Grow Pink Hydrangea Plant Food.

Hydrangeas should be pruned twice a year – in winter and in summer,
The winter pruning (ideally in June or July) is the harder pruning session. Remove all the dead, old or weak stems. Prune all the remaining stems back to just above a cluster of buds. The idea is to channel all the plant’s energy into producing new flowers. After pruning, feed with hydrangea food and mulch the soil well (an acidic mulch like pine needles works well if you are aiming for blue flowers).
Summer pruning (ideally at the end of January) entails cutting off any dead flowers and removing dead or old stems. Add plenty of compost to the soil to encourage the next season’s growth and mulch well to conserve water in the soil.