Water-wise gardening – is it still relevant?
Saving water should still be high on the gardening agenda, despite the wettest year on record.
10:11AM GMT 08 Jan 2013
CommentI fondly remember a holiday trekking in the Hunza Valley, high in the mountains of northern Pakistan. There was not much native vegetation, partly because we were travelling through high-altitude desert and partly because the oasis around which we were walking was so intensively cultivated. The Hunza Valley climate is unbelievably harsh: bitterly cold winters and viciously hot summers. Yet the few wild plants we saw were strangely familiar: two were native to Britain, sea buckthorn and the Burnet rose; and two were instantly recognisable from gardens at home, the yellow-flowered Clematis orientalis and Russian sage (Perovskia atriplicifolia). It was a powerful reminder of just how tough some of our garden plants are.
While a year of heavy rain has convinced many of us that “traditional English weather” is back, I believe that this is an aberration. There is no getting away from the fact that we have come very close to severe drought conditions over much of the country in the past few years and my hunch is that this is the long-term trend for our gardens.
Two recent dry years (2010 and 2011) also coincided with much colder winters than we have been used to; we got away very lightly in the winter of 2011 but the European mainland had massive snowfalls and record low temperatures. In the minds of many, the idea of global warming has gone hand-in-hand with a trend for drought-tolerant gardening, and the assumption that we are moving towards a drier, warmer climate. As a result, sales of olive trees have rocketed. The dream of living the Provençal lifestyle in London or Dorset has seemed seductively real.
However, there is some evidence now being discussed in scientific circles that a drier but colder climate is the long-term trend. Freezing, Continental-style winters will come as a shock to British olive growers – how should gardeners react? To me, it increasingly makes sense to grow more perennials from central and eastern Europe – these incredibly tough, hardy plants can take whatever the heavens throw at us. But in any climate, conserving resources is the key to good gardening. Water management is vital, whether we have too much of it or too little. So let’s build on the hard-won wisdom that we’ve accumulated over the last three decades.
The dry Seventies
The dry summer of 1976 was a wake-up call to many. Help was at hand though, from Beth Chatto and her book The Dry Garden (1978). Beth pointed out what seems obvious to us now, that plants should be placed in the garden according to their habitat, so if we have dry conditions we should look to dry environments for suitable plants. She followed up her “habitat planting” with a very successful gravel garden on the site of a former visitor car park. It was by no means the first gravel garden, but its attractive design and Beth’s ability to write enthusiastically about it inBeth Chatto’s Gravel Garden (2000) promoted the concept.
Designers loved the gravel garden; it enabled them to create spaces that looked both contemporary and instantly established. The gravel keeps the soil cool and moist, and acts as a wonderful foreground to the sophisticated silvers and greys of much drought-tolerant planting, and to many flower colours too.
It did not catch on as widely as one might think, however. Once made, it is difficult to change. Every time you put in a new plant, it is almost impossible to avoid mixing soil and gravel, which provides a habitat for weeds. Gravel gardens also often look out of place with older houses, while many people simply do not like the look.
An Eighties mulch
In the Eighties, gardeners began to discover mulching as a way of suppressing weeds and keeping soil moist. Mulching grew from the organic movement, but its use of waste plant material and straw only really made sense for vegetable growers. When the forestry industry found that its waste materials could be sold off to gardeners, the use of mulch for ornamental plants took off. Chipped bark or wood became almost universally available by the Nineties.
But it can be expensive to mulch a whole garden. Unlike gravel, woodchip mulches eventually rot down and have to be replaced. Mulching also only works with permanent planting of shrubs or long-lived perennials. It offers little to annual or mixed borders where gardeners like to shoehorn in summer bedding or bulbs, or make other changes.
Selecting appropriate plants and keeping moisture in the soil by mulching are passive strategies for dealing with drought. But lots of gardeners still want to to grow “thirsty” plants, such as summer bedding and container plants. Along with the rise in home vegetable growing, this means there is still a huge need for more proactive water management.
Captive water
From the drought of 1976 onwards, the use of waste water or captured rainwater has been increasingly promoted, and gardeners now have a wide range of water butts to choose from. Devices to direct water from downpipes into butts are a boon, and for those who are determined to save every last drop, it is now possible to buy kits which link butts together.
Grey water from washing can be safely used on plants – just be careful with the bleach. Gathering grey water is problematic, however, and can be made worse by the design of modern homes, which puts pipework on the inside, so making use of this source of water tends to involve much Heath Robinson technology.
The rain garden is the most recent development in water-wise gardening and attempts to address the issues of both flooding and drought. It is a holistic system that captures water from rainfall, steady or torrential, and keeps it in the garden, rather than channelling it into the overloaded sewage system.
Climate change does seem to involve an increasing number of extreme weather events – droughts alternating with sudden downpours. The rain garden concept offers a storage solution to capture as much of the downpours as possible and to minimise water loss. A key concept is the swale – a depression designed to temporarily hold water after a heavy downpour, allowing it to slowly seep into the surrounding soil and replenish the water table.
Swale planting uses the many perennials which grow in averagely moist soils but which can survive an occasional flood: good examples are Iris sibirica, most cranesbill geraniums and the long-flowering Persicaria amplexicaulis.
Future tactics
Research by institutions such as the Royal Horticultural Society will be a vital tool in improving our ability to combine attractive gardens with sensible water use. An example is a recent study conducted by the RHS which showed that container plants do not need the high levels of water they are often given, and even flower better with less than what was conventionally regarded as “optimum” water.
Another study showed that some commonly grown silver-leaved Mediterranean plants such as Lavandula angustifolia and Stachys byzantina are more tolerant of occasional waterlogging than was previously thought, which makes them much more attractive to gardeners who may experience alternating drought and flood.
Gardeners wanting to be water-wise but also hardy enough to withstand cold winters need to forget the Provençal or Tuscan lifestyle. Instead, they should look east: the steppes of central Asia may not be as romantic but they may have more plants to offer. Dry steppe-type habitats start to appear around the longitude of Berlin and Vienna; they are fantastically rich in flowers, often with striking ornamental grasses and rich bulb floras.
A recent garden which illustrates the cold and dry look (on very poor soil) is Piet Oudolf’s Scampston Hall – a romantic haze of perennials and grasses at a height of about a metre. An advantage is that among them there are many evergreens and plants with good winter seed heads; nothing needs staking, weeds do not flourish in dry soils, and there is not too much dead material to cut back at the end of the year.
Goodbye Tuscany, hello Kyrgyzstan.
