Every garden needs a hydrangea or two. Most of the hydrangeas found in British gardens today originate from China and Japan. In the Far East hydrangeas have been cultivated for well over a thousand years, and it’s easy to see why they have been popular down through the centuries – and why they were such a big hit when they were first introduced to Europe. Tolerant and simple to grow, hydrangeas put on a stunning display right through into late autumn, bringing voluminous amounts of colour and cheer at a time when most gardens are starting to look a little thin. What’s more, they make splendid cut flowers, and you can dry the flower heads for even longer-lasting decorative appeal.

Novice gardeners often assume spring is the best time to introduce new plants into the garden, but old-timers are well aware that this isn’t always the case. Most shrubs – and hydrangeas in particular – fare better when planted out in autumn than when planted earlier in the year. To understand why, look at it from the hydrangea’s point of view. Plant it in spring and you’re disturbing its roots at precisely the time its biological clock is demanding that it put on a spurt of new top growth – all very stressful! Plant out the same shrub in autumn and it has already done the majority of its growing for the year; this means it has nothing much else to do except spend a month or two consolidating its root system before winter comes. Result: less stress, and a happier plant the following year.

flower heads come in two different forms, known as ‘mopheads’ and ‘lacecaps’

HEADS UP

The two species of hydrangea most commonly cultivated in Europe are Hydrangea macrophylla and Hydrangea paniculata. Hydrangea paniculata is hardier and more adaptable, but it is the showier, more colourful Hydrangea macrophylla that is by far the most popular with gardeners. Hydrangea macrophylla flower heads come in two different forms, known as ‘mopheads’ and ‘lacecaps’. Mopheads, as the name suggests, produce groups of flowers in large, globular clusters. Thanks to their dramatic impact these are highly prized by flower arrangers. Mophead hydrangeas make impressive specimen plants and work particularly well in formal garden settings, placed either side of a gate, doorway, bench, path or other structural feature. Hydrangea macrophylla ‘Miss Saori’ is a particularly stunning mophead that was awarded the title ‘Plant of the Year’ at last year’s Chelsea Flower Show.

Lacecaps are less widely grown, but to my eye make a more attractive and subtle display. Lacecaps have flat flower heads composed of a tight group of small, fertile flowers surrounded by a ring of much larger, showier infertile ones (the same arrangement that is found in Viburnum opulus, the guelder rose). Lacecaps look better than mopheads in relaxed, informal gardens, creating a loose, woodland atmosphere and slotting in nicely under trees or larger shrubs. Hydrangea macrophylla
‘Taube’ is an especially elegant example of a lacecap, and one of my personal favourites.

A SHELTERED LIFE

In general hydrangeas are easygoing plants that will thrive in most soils other than seriously waterlogged ones. That said, there are two extremes that must be avoided when choosing a site for your hydrangeas: too much midday sun, and too much wind. Give them a sheltered spot in partial shade, though, and they should be happy enough. Hydrangeas are hardy enough to cope with a normal British winter, but in the event of a blast of Arctic cold it would be wise to wrap a layer or two of horticultural fleece around them to keep them safe and sound. Mulch your hydrangeas with well-rotted compost every year to improve the soil, and feed them annually in spring. Be careful not to over-feed, though, or you’ll end up with a plant that’s all leaves and no flowers. Hydrangea macrophylla and Hydrangea serrata can both be pruned in the same way, namely by cutting up to a third of existing stems back to the base in winter. This will encourage new growth and heavier flowering on the stems that remain. If you’ve inherited a neglected, straggly or otherwise misshapen hydrangea, be prepared to be radical. Chop all the stems right back to a centimetre or two above ground level and you’ll find it will soon grow back. You won’t get any flowers the first year after pruning (these two species flower on old stems) but the end result will be a healthier, better-looking plant.

ALL CHANGE

Several species of hydrangea, and in particular Hydrangea macrophylla, have long fascinated gardeners due to the fact that the colour of their flowers changes according to the acidity (pH) of the soil. On an alkaline soil the flowers will be pink, whereas on an acid soil they will tend to become blue – often quite startlingly so, as with the heavenly Hydrangea serrata ‘Bluebird’. If your garden soil is alkaline or neutral, growing your hydrangeas in containers in ericaceous compost will give you maximum control over the pH of the soil. If you plant them directly in the ground then you will need to make a little more effort to achieve that gorgeous hydrangea blue. A quick fix to acidify your soil is to mix aluminium sulphate or iron sulphate into it; proprietary mixtures containing these substances are widely available from garden centres. If you prefer a more natural – albeit rather more long-term – approach, work well-rotted leaf mould, finely shredded pine bark, coffee grounds, crushed up egg shells or chopped citrus peel into the soil at regular intervals. Whichever method you use, don’t under any circumstances water your hydrangeas with tap water if you live in a hard water area, otherwise you will be introducing lime back into the soil and losing that precious edge of acidity. Wherever possible, save rain water and use that.