RHS Journals
The Garden
September 2007
Time for a new approach in gardens
Many gardening techniques have altered little in generations but, as Matthew Wilson suggests in his new book, concerns over climate, interest in sustainability and new understandings of natural processes may make change inevitable.
Images: Lee Beel
When I left horticultural college 15 years ago, I was still a rank novice, yet equipped with a basic grounding in the technical and practical aspects of gardening. In many respects my formal training was already out of date at the time I was eagerly absorbing it. Plant hardiness, the use of pesticides, the role of beneficial predators and overarching environmental concerns were just some of the subjects that were being challenged or embraced - but I would have to discover more about these myself, from without the hallowed halls of education.
I feel that the biggest lesson I have learned since leaving college is that whatever we do in our gardens, nature will always win out, so far better to be in tune with it than deploy prescriptive, outmoded practices. The weather in Britain has always been changeable but is becoming more extreme: spring 2006 was cold and wet, followed by a blazing summer - this year was the reverse. So what good is it to simply stick to traditional advice, reciting, parrot-fashion, ‘plant in April’, when April may actually be hot and dry like July, or frosty and damp, more reminiscent of February? And does it really matter if our lawns have a few daisies and our roses a few aphids? Rather than going straight into battle, is it not better to retune our aesthetic antennae and garden more sympathetically both with nature and our changing climate? I certainly think so.
Wise ways to water
Water use was never really discussed during those distant college days; all I can recall is the standard advice of ‘water well in dry weather’ for particular plants, much as can be found on plant labels to this day. But water is a resource that we have no right to take for granted; as this summer has tragically demonstrated, we can swing from having too little to far too much in a matter of weeks. Unfortunately, unlike in many continental European countries, there has been little encouragement for householders and property developers to install water-harvesting systems as a matter of course. Instead we rely on low-capacity water butts that quickly run dry when we need them most.
Applying water responsibly is something we should all embrace. Garden sprinklers use profligate amounts of water, with up to 85 percent being lost through evaporation - great if you enjoy handing your money over to the water company, not so good for the environment or your bank balance. Watering cans, on the other hand, make you really think about what you are watering because of the effort required to fill and empty them. Recycling grey-water (such as used bath water) is something we can consider too, especially for non-food crops.
Choosing your plants
If gardeners start with the basic premise of good soil management and correct plant choice, the need to water excessively diminishes. The Main Borders at RHS Garden Harlow Carr were redesigned and replanted in 2005, and have had no artificial irrigation beyond initial watering-in. Since planting they have withstood two extreme Julys: the record-breaking hot one of 2006 and the dismally wet one of 2007. We deployed really thorough soil cultivation at the start, using the correct improvers (Harlow Carr’s primarily clay loam is fertile enough, so grit, spent mushroom compost and composted bark were used to improve drainage and structure rather than boost nutrients), and selected plants with near-identical requirements. We top this off with a thorough mulch each spring, and the borders now thrive without excessive intervention of any type. This is key to sustainable, and successful, gardening.
The prescriptive overuse of fertilisers and inappropriate soil improvers leads to sappy, limp plants that are prone to wilting in hot weather, require staking and tying in, and are more likely to attract sap-sucking insects that just love that overfed, plump foliage. Creating a community of plants that enjoy the prevailing conditions in your garden without too much extra input gives aesthetically pleasing results without a high environmental cost, mainly because such plants simply look right together. It is the old adage of ‘right plant, right place’ that is understood by most gardeners but sometimes forgotten when faced with a nursery or garden centre full of desirable flora.
Controlling pests
Perhaps the biggest shift in thinking in the last few years for me has been in the use of pesticides and inorganic fertilisers. At college I was taught to be a killer, and encouraged to obtain the relevant sprayer certificates. Chemical intervention was promulgated as the first line of defence in gardening, as if somehow we could hold back the waves of plant pests with Canute-like arrogance. I do not like using synthetic chemicals in the garden, not because I am an organic convert (actually, I believe that the overbearing, preachy tone of some exponents has set back the cause of low-input gardening, rather than advancing it) but because it is demonstrably possible to garden without them or to use them only as the last resort.
Simply encouraging a balance of natural predators and their prey, and maintaining those levels by installing habitat boxes and/or leaving perennials standing through winter, will provide the all-important food sources and overwintering habitats. This also means avoiding the kind of monocultural plantings that encourage pests and diseases, such as the traditional rose gardens that are a feature of many parks and gardens - including the Society’s own gardens. When visitors to Harlow Carr comment that the roses in our mixed borders have aphids I give a little cheer; no aphids means no ladybirds, lacewings, hoverflies and blue tits. If a few aphids really bother you that much it is worth taking a moment to remember, before reaching for the pesticide spray, that the manufacturing and waste management involved in the production of such chemicals has led to some serious environmental and human consequences.
Clever cultivation
Correct methods of planting also help create a healthy garden more able to withstand our changing climate. Often people plant too deeply, the ‘neck’ of the plant below, rather than at, soil level, leading to neck rots. Simply digging a hole, filling with compost, and inserting the plant will not help much; especially on heavy soil this can create a water-filled ‘sump’ for the plant to drown in.
Tree planting is an interesting area of new thinking; trees are now planted in a shallow, square pit (rather than deep and round) with modest soil improvement for better root growth. Planting on a mound in heavy soil prevents waterlogging, and staking with a short, angled stake allows the trunk to flex and strengthen (above).
Revised thinking has also changed how we manage established plants. Practicing the ‘Chelsea chop’ on herbaceous perennials (cutting them back in early summer; see The Garden, Aug 2005, pp576–579) prolongs flowering and results in more compact plants.
Managing the soil
One aspect of my college training that had remained largely unchanged for decades was soil improvement. The science behind understanding the composition and characteristics of soil is still valid, but what we do to improve our soil is a different matter. Healthy soil relies on the presence of soil flora and fauna, as well as the ‘correct’ balance of air, water, minerals and organic matter.
One of the key methods of improvement promoted for soils of almost all types, double digging, may have a place in some situations - new borders on fast-draining soil, for example, or where a deep root run is needed for vegetable crops - but as a catch-all, it fails. Heavy soils with shallow topsoil become an impenetrable, gooey mess when double dug with binding manure, and the continual disturbance of the animals and micro-organisms that help to improve structure and fertility by processing organic matter can hardly be considered a good thing either. Soil moisture can also be seriously depleted by excessive digging. Switching to a low- or no-dig regime, where soil is improved by surface application of organic matter (which also acts as mulch) allows soil dwellers to thrive, maintains moisture and reduces the need for osteopathic treatment. This works just as well for vegetables as for ornamentals, as I found on my allotment during the dry weeks of April.
RHS New Gardening: How to garden in a changing climate, by Matthew Wilson, published by Mitchell Beazley in association with the RHS, 224pp, ISBN 9781845333058. RRP £18.99 RHS price: £15.99 RHS mail order: 0845 260 4505 or buy online from the Wisley Shop.
Matthew Wilson is Head of Site and Curator at RHS Garden Harlow Carr, North Yorkshire
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