Given the perfect position and the right feeding, hydrangeas are easy to grow.
Photo APN
Hydrangeas are loved and loathed in equal measure. They are one of the plants most likely to be mentioned in a design consultation – second only to a request for a lemon tree – and they’re as much a litmus test of a client’s taste as they are the condition of the soil. They may seem like a classic plant, but they only became popular in Europe after botanist Sir Joseph Banks brought them back from China in the late 18th century. But as they appear centuries earlier in art and literature, especially in Holland, it’s a mystery why they were less popular elsewhere in Europe, particularly in England.
These beautiful flowering shrubs remind me of my grandmother painting watercolours in her garden, surrounded by old cracked saucers, each covered in swirls of paint, with the colours spreading across the thick paper and drying quickly in the Hawke’s Bay heat. Yet my garden is such a hodgepodge of trial and error, it came as a surprise to me recently to realise I didn’t have a single hydrangea among my commoners and collectibles. After a quick assessment, it was clear I’d have to remedy the situation by taking the spade to a less-favoured plant.
Given the perfect position and the right feeding, hydrangeas are easy to grow. They deliver flowers from spring to autumn, with colours that shift to suit the light of the seasons. Although hardy, they are fussy about aspect, so are ideal in positions with morning sun and good shade in the afternoon, as long as water is consistent. Avoid planting them in heavy clay soil. Use ample compost and continue to reapply every year to keep the plants looking good. Liquid-feed monthly through the growing season or apply sheep pellets in spring and summer.
For a position with full sun, try Hydrangea paniculata, a variety that grows well in those parts of New Zealand where it freezes in winter. They can be pruned at any time without affecting the flowering, except when coming to bud. They can even be trained into a tree form. The more common variety is the moptop, Hydrangea macrophylla, which offers the widest colour range.
Maintaining the colour you want isn’t always easy, so don’t be surprised if after planting your pinks turn blue or vice versa. This is an indication of the soil’s natural condition. The colour of white blooms can’t be manipulated, but you can play with the pinks and blues, although the results may not be permanent.
Aluminium is the key ingredient for colour. My great-aunt used to bury old cans beneath a hedge of hydrangeas in the belief it would keep them blue, but the cautious addition of aluminium sulphate to well-watered soil in the growing season is probably more reliable. For blue hydrangeas, soil also needs to be slightly acidic. The simplest way to ensure this is to apply compost or lawn clippings as mulch. Avoid having a thick layer, though, as lawn clippings can become smelly and the high temperatures during decomposition make them an ideal breeding ground for flies.
For pink hydrangeas, you need to restrict aluminium uptake by adding dolomite lime to make the soil more alkaline, and a fertiliser with a high phosphorus content. Planting near a concrete path can also affect the colour because the lime leaches from the cement and raises the pH level. The intensity of the colour, however, depends more on the plant’s health and age.
When I first started gardening, I worked for an elderly man who wouldn’t let me touch his hydrangeas. Instead, he took to them every autumn with electric hedge trimmers. His was one of best hydrangea hedges I’ve ever seen, so clearly little fuss is required. As plants mature, they respond well to being shaped, so pruning is the only other requirement – although it needn’t be every year. As a rule of thumb, trim no more than a third off at the end of autumn. Start by removing dead wood.
Most hydrangeas are deciduous, so beginners need to distinguish between dead and dormant wood. Dead wood is a silvery colour whereas dormant wood remains brown. If you are unsure, scratch the surface of the bark. If the wood is still alive, a thin layer of green will be revealed. Cut down to 5mm above two healthy leaf tips or nodes (these are the growing tips). If you trim off too much, you will get fewer blooms the following year, as they flower from dormant buds, not on the new wood.
As well as being easy to grow when well-positioned, hydrangeas will also grow easily from cuttings. Ideally, a cutting should be taken from a growing tip that hasn’t flowered in the previous season. When you cut it from the plant, count down five sets of leaves or nodes and cut beneath cleanly. Remove all the leaves except the top set. Start the cutting off in a jar of water or a sandy mix. To increase your chances of a good strike, dip the cut end in rooting hormone, which is available from garden centres. If the cutting is growing in a sandy mix, keep it watered, and if it hasn’t developed roots within a month, start again.
If you want to dry hydrangea flowers, late autumn is the best time – it’s also the time of year they will be flushed with beautiful antique tones. The secret is timing rather than method, and they will last for years if properly dried. Ideally, the blooms should be dry on the plant before being picked, then hung upside down in a dry place. If you want strong colour, dip the dried blooms into a boiling hot vegetable dye, as you might dye cloth. Be warned: they will make a mess of the floor, so choose your location carefully.
Of course, freshly picked blooms are the best, and anyone can throw a bunch together to make an elegant display. A plant in the garden is worth a small fortune in cut flowers, which are also perfect for weddings. In China, the tossing of these “embroidered balls” by an unmarried woman into a crowd of eligible men is believed to find her a husband. Although I’m sorted on the husband front, I’m sharpening the spade to make room on the hill for just one or two hydrangeas.