The greening of gardening

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Sep 22nd 2008
From Economist.com

Horticulture will change as the climate does


GARDENS are more than just yard decorations for the green-thumbed: they also express a worldview. As concern over climate change grows, environmentally sensitive gardens are becoming more popular. Many gardeners try to conserve water and avoid the use of pesticides, preferring instead biological controls, manual removal and companion planting, in which certain plants are grown next to each other to protect both from pests or diseases. Commendable as these measures are, they are only a beginning.

Gardens need not change in the way that a natural ecosystem must in response to climate change. With humans around to pluck out unwanted weeds and provide nutrition, garden plants are cosseted, and thrive in non-optimum conditions, because they are not subject to the struggle for existence that plants in the wild are.

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Still, gardens of the future are likely to change for two reasons. First, warmer weather will transform the gardener’s palette (the olive tree and the potted citrus, for instance, will continue their northward invasion via the middle-class gardens of Europe). And secondly, gardeners may realise that they can be greener by changing what they grow.

Horticultural fashions change constantly. The 1950s British cottage garden features delphiniums, rhododendrons, foxgloves, lupins and azaleas. The modern gardener—concerned as she is with “structure”, “texture” and “form”—might sneer at such gauche displays of showy flowers. Out go the daffodils and ox-eye daisies, and in come tree ferns, cycads, bamboo, ornamental grasses and Japanese maple. But what else will change?

Broadly, gardens in the northern hemisphere will be uprooted and moved southwards, horticulturally speaking. In places that are currently hotter and drier, such as Spain and parts of the Mediterranean, gardeners will come to appreciate the charms of cacti and succulents.

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In drier but more temperate places, it might be time to rethink the lawn. Grass is thirsty. On the Royal Horticultural Society’s website, Richard Bisgrove, a senior lecturer in landscape management at the University of Reading, suggests planting little thickets of drought-resistant plants in gravel. Chamomile likes hot, dry soil and smells great—it could make a lovely lawn in low-traffic areas.

Gardeners will also have to ask themselves whether the plants, fruits and vegetables they are growing remain appropriate—growing, say, tomatoes in water-stressed areas of the world is not exactly green. Figs might be better.

Similarly, one might also consider how environmentally friendly it is to buy new annual-bedding plants each year from the garden centre, rather than growing them from seed. More radical still might be to wave a permanent goodbye to the tiresomely-thirsty pansy, and say hello to the more resilient geranium.

In America’s hurricane corridor, offering gardening advice seems somewhat beside the point. But elsewhere, more extremes of rainfall (a lot all of a sudden, then none for a long time) are to be expected.

Earlier this year, The Tyndall Centre for Climate Change Research and the University of East Anglia’s Climatic Research Unit, looked at what a British garden might look at in 2050. Intense rainfall, it warned, leads to nutrients being more easily washed out. Gardeners will need to respond by digging in organic matter and mulching.

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Tyndall’s entry in this year’s the Chelsea Flower Show shunned the use of concrete, which is impermeable to rainwater and contributes to flooding (because water runs off so quickly). The Tyndall garden has a path made from an innovative porous material made from recycled Cornish china-clay waste.

Gardens in a warmer climate will also find they have longer growing seasons and fewer frosts. That may be good for the geraniums, but some plants and trees—apples, pears, plums, rhubarb and raspberries—need cold spells to stimulate flowering and fruiting. Pine and beech trees need cold to start forming leaves.

Milder winters and warmer summers also mean more pests; aphids, spider mites and thrips will all increase. Insects from elsewhere are also likely to present new problems for gardeners. On the other hand, new pests will also bring their predators. In the garden as elsewhere, a changing climate present threats and opportunities, particularly for the green-minded and green-thumbed.