In a Sydney summer hydrangeas are as blue as a clear day and as fat as a Christmas pudding. They were stalwarts of Edwardian planting schemes, so nestle against the easterly and southerly foundations of many an old Sydney home. But they also do well in pots so are summer treats for small-scale, low-sun gardeners. In fact many varieties do better in pots than in the garden as the root constraint triggers increased flowering. Container-growing also allows gardeners to position them for morning sun, but afternoon shade; to accede to the hydrangea’s desire for free-draining soil but plenty of water; and to hide them when they are bare sticks in winter.
It’s also easier to control the colour of hydrangeas in pots. White hydrangeas are always white, but coloured hydrangeas range from blue to pink depending on the amount of aluminium in the soil. Aluminium is linked to pH. Blue hydrangeas need a pH of 5 and under; pink ones want something above 6.5. (Yates has made this simple for the unchemically-minded and released ready-mixed Hydrangea Blueing or Pinking Liquid. Just follow the instructions.)
The fat mopheads, and the flatter lacecap types are both Hydrangea macrophylla. Most flower just once (the ‘Endless Summer’ range has been bred to repeat flower) but the flowers last a long time. That’s because what we think of as the flowers are actually the bracts supporting the tiny short-lived flowers in their centre. As the bracts age, they turn lovely colours from green to dusky pink and burgundy, often freckled. To enjoy this late show don’t be too eager to prune. Just snip off any scorched blooms in January.
Prune the plants in July by first cutting out a few of the oldest stems. The bark on the old stems starts to peel as they reach the end of their productive life so are easy to identify. Next cut the spotty pale green stems that flowered this year back to a pair of fat buds. The buds lower down the stem that are narrow and black are leaf buds. If you prune back to these you’ll miss some flowers. Leave the unflowered stems to flower next year.
There are others in the family to discover: The fluffy white flowers here are H. arborescens ‘Annabelle’.
This hydrangea flowers on slender stems with emerald green foliage, and because it flowers on new growth it can be brutally cut back in winter – no bare sticks. H. paniculata and H. quercifolia are both more tolerant of dry spells than the others. Paniculata, as the name suggests has panicles of flower. Some varieties have bracts that turn from white to a rich pink as they age. Look for ‘Pink Diamond’ (available from Flemings) and ‘Sundae Fraise’ (available from Lambley). Quercifolia, the oak-leaf hydrangea, turns a lovely burgundy in the cold. It’s a subtle garden presence. For something louder choose the ‘Mai-ko’ hydrangeas, which were bred in Japan from re-imported ‘European’ versions of Japanese natives. They are compact plants designed for pots in vibrant colours with a white margin on the petals.
To decorate the Christmas table with bowls of hydrangeas, get out early in the morning with secateurs and a bucket of water. Plunge the stems in the water immediately to wash away the sticky white sap that can prevent water being taken up the stem and cause them to sag unhappily. As long as they aren’t placed in direct sun they’ll cheerfully welcome in the New Year.