Gardening in a changing climate
Adaptation: the key to survival
Meeting new challenges
2006 and 2007 have highlighted the unpredictable impacts of our weather on growing conditions in a way that has few if any historical precedents. As Mike Calnan, Head of Gardens and Parks for the National Trust says, ‘In 2007, Trust properties that have never been flooded before were affected: even Hidcote, on the top of a hill, was hit by localised flash floods, whereas in 2006 the biggest issue for most of the Trust’s properties was drought-related plant stress.’
The National Trust works with two basic principles regarding changing climate - adaptation and mitigation (by predicting problems and taking action to avoid them). Mike realises that the future may pose difficult challenges. ‘We’ll do what we can that is environmentally acceptable to maintain our gardens, but we recognise that in the future our hand may be forced and we will need to use plants that differ from those that are historically accurate. In extreme cases we may have to abandon our conservation principles in some gardens.’
This work is not restricted to the boundaries of the Trust’s gardens: Mike and his colleagues are working with farmers to reduce soil erosion from nearby fields into the gardens, and nitrates leaching into watercourses.
Find out more about the National Trust approach
Adapting trees and shrubs
At Sheffield Park, East Sussex, Head Gardener Andy Jesson has been leading the restoration (started in 2002, with the aid of a major fundraising campaign) of this magnificent landscape garden. With impressive collections of mature trees and shrubs, the garden suffered in the Great Storm of 1987 and subsequent gale of 1990. However, it also seems to be in general decline: a result, perhaps, of changing climate. Central to the restoration - in a garden where fertiliser, peat, irrigation and pesticides are not used - is the collection of seed from plants that have proved able to cope with the conditions there. ‘We grow these on and plant them as small plants, two or three years old,’ says Andy. ‘By combining the benefits of local provenance and how this affects genotypes [the genetic make-up of individual organisms] with the virtues of planting small, I believe that these new plantings will stand a better chance of surviving future climatic challenges.’
Controversially, as well as subscribing to this survival-of-the-fittest approach, Andy also believes that ‘plants have the ability to adapt to their environment to a degree’, and cites the natural regeneration of beech woods at Toy’s Hill in Kent (right), ravaged by the 1987 Great Storm, as an example: ‘those that have regenerated naturally from seed are 2-3m (6-10ft) taller than planted saplings’.
The benefits of planting small have also been observed at RHS Garden Hyde Hall. Plants in the successful low-input Dry Garden were little more than 9cm (3.5in)-pot-sized subjects when planted, and trees in the 35ha (86 acre) Wild Wood were just one- or two-year-old whips. Forced to adapt to Hyde Hall’s heavy clay and exposed, dry conditions, these trees are reaching 3m (10ft) or more in just three seasons, and should be developing far greater resilience as a result.
Historic bedding
At Nymans garden in West Sussex, Head Gardener Ed Ikin and his team face challenges in a garden where plantings of historical significance are a major draw for visitors, but are at the same time proving environmentally problematic.
Nymans’ twin Summer Borders (right), where annual plants are bedded out to dazzling effect, provide a good, historically sensitive example. Yet during the searing heat of 2006, irrigation to the borders was cut from twice a week to just four times during the entire season. This extraordinary achievement in such hot, dry conditions - with plants as varied as petunia, heliotrope, cleome and antirrhinum - was not achieved without research and effort.
Green-waste compost was used both as a soil improver, dug in before planting, and also as a mulch after planting. An unexpected bonus, as Ed discovered, was that ‘the lack of irrigation also meant that plants were more compact, with harder growth, making them less prone to aphid infestation, allowing us to cut out pesticides’. The borders were inoculated with mycorrhizal fungi to work symbiotically with the plants, improving vigour and reducing diseases - an avenue now open to home gardeners, thanks to off-the-shelf products available at many garden centres.
The fact that a garden reliant on ‘traditional’ plants and plantings can manage them in an environmentally-aware manner both gives hope for the preservation of historic bedding displays, and indicates that the other traditional garden features that many of us enjoy in our own gardens, such as herbaceous or mixed borders, still have a future.
New mixed borders
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| The Main Borders at RHS Garden Harlow Carr have been remade with plants that are suited to the site and need less maintenance than those they replace. The effect is similar to a traditional mixed border, but the plants are never watered, fed or sprayed with pesticides, and need no additional support | The Dry Garden at RHS Garden Hyde Hall is a fine example of planting carefully chosen to thrive in the on-site conditions. This style, however, is not the only one that will suit such situations in the future; with certain modifications, more traditional garden styles should also succeed. |
Permanent plantings offer even greater scope for toughing out the vagaries of changing climate. Hyde Hall’s Dry Garden may well include fleshy-leaved succulents such as Sedum and Agave and silvery xerophytes including Lavandula and Convolvulus cneorum, but it is also home to many more widely grown plants, such as hardy salvia, Euphorbia and Cistus (rock roses).
At RHS Garden Harlow Carr the Main Borders, dating from about 1950, were replanted in 2005. Amazingly, these borders have never been irrigated (or fed, or sprayed with pesticides) beyond a single watering-in after planting. As well as tougher, less disease- and pest-prone plants, an added benefit is that staking and tying-in of overly lush plants is not needed.
The secret to these successes lies in plant selection. Choosing plants that thrive together, because they - or their forebears - come from the same or similar growing conditions, is the simplest way to garden more sustainably, with less water, fertiliser and pesticide use.
This approach to planting was described by landscape architect James van Sweden as the ‘creation of communities of plants that will thrive with one another without any need for artificial intervention, merely good gardening practice’, but most gardeners have known it for years as simply ‘right plant, right place’.
This approach tends to be applied to perennials and grasses, but the thinking behind it is equally applicable to woody plants, so Harlow Carr’s Main Borders feature a mix of grasses, perennials and woody plants from North American prairies, Eurasian steppes, the Mediterranean basin and the South African veldt - all of which have conditions that, increasingly as changing climate begins to bite, can be applicable to parts of the UK. These plantings, performing as traditional mixed borders, but able to resist our now even more unpredictable weather, show the way forward for domestic gardeners.
Find out more about the RHS approach
Cottage garden style
In my own, small garden - 18 miles from Harlow Carr - conditions are drier and warmer, and the soil is better drained. Some plants have failed in my garden that thrive at Harlow Carr, but I have established a community of self-supporting perennials, grasses, shrubs and annuals that need almost no intervention from me, save for some tying in of climbers and an annual cut back and thorough mulching in early spring. Many of the plants are those used in expansive ‘naturalistic’ planting schemes popular on the Continent, but when assembled on a smaller, mixed scale, they become loose, billowing and relaxed, and my visitors tend to describe the planting as being ‘cottage garden’ in style.
Lawns
And need that bastion of UK gardens, the lawn, be lost? Often intensively managed, it is increasingly replaced by gravel or hard landscaping. Yet allowing a few weeds and keeping the grass longer can help it resist drought, as will improved aeration and scarification in autumn. A brown lawn will recover, but plant breeding may hold the key, by developing more drought-resistant turf grass cultivars.
Find out more about dealing with turf and lawns
The future?
Perhaps the future for successful gardening lies in better understanding the incredible qualities of plants, allied to our innate ability to adapt, question existing techniques and create innovative new practices. And just as the threats are many and various, so might be the opportunities and solutions.
Plants deploy multiple adaptations to cope with challenging conditions and in doing so have clung tenaciously to nearly every part of the planet. It is important we take heart and learn from them, and adapt our planting styles and plant selection accordingly.