How about a brief relook at gardening and climate change?

I originally published a series of four articles about gardening and climate change in 2013 and reposted them in 2015. Reports of a strong ‘El Nino’ effect forecast for the past few years coupled with man-made global warming seem to have resulted in more dramatic weather events, albeit the results in the UK might be a little gentler than typhoons and droughts..the latest horrific wild fires in Australia, flooding in several places and the continuation of polar ice melt AND the heightened profile of climate change through Extinction Rebellion, Greta Thunberg and young people’s protests around the world, suggest that a republishing of these four articles might be timely…

In this first of a series of posts about gardening and climate change, I explore just what the experts are predicting for the UK and what this might mean for our current gardens and gardening techniques.

I think it was Nietzsche who said that madness comes not from uncertainty but certainty. But for the gardeners of Britain, pulling their hair out in the face of ‘the wrong weather at the wrong time’, climate change and the unpredictable weather it is bringing us can frustrate even the most seasoned horticulturist, though perhaps stopping short of madness! It poses significant challenges to gardening customs  and practices, which have in the past been based on the predictable passage of the seasons within fairly certain timings and within, by and large, expected bounds of temperature, wetness, wind and frost (though in the maritime setting of the UK these can all vary considerably from area to area). So maybe we need to look upon these greater levels of uncertainty as a challenge and one which will actually be mentally stimulating!

The underlying changes have already begun to unfold in the UK (and elsewhere):

• A gradual, overall rise in average temperatures

• Increased frequency of extreme weather events like rain and flooding, frost and snow, wind or drought

A few years ago a seminal article on the impact of climate change on gardening in  the UK (‘Gardening in the Global Greenhouse’ by Richard Bisgrove and Paul Hadley of the University of Reading) pointed up these trends and started the debate about what they will mean for Britain’s gardens. The main conclusions were:

• reduced frosts

• an earlier spring

• higher average temperatures all year round

• increased winter rainfall, leading to increased risk of flooding 

• hotter, drier summers, leading to an increased risk of drought.

They pointed to how these trends were likely to make looking after large areas of lawn and grass increasingly difficult and costly, and how some traditional garden features may have to be replaced by new ones, more suited to changing conditions (e.g. loss of some ‘cottage garden’ favourite plants). Arguably there is even a greater challenge for heritage gardens, which have traditionally featured large lawns, herbaceous perennials and specific planting combinations and effects which were developed in climatic conditions that will gradually disappear.

It also seems that there’s something of a north – south split in the UK, with the south becoming warmer and drier and the north subject to wetter weather, in the winter especially, though recent storms and flooding in the south west and southern Britain might seem to run ounter to this trend.

On the plus side, botanic gardens have had to be intensively managed in order to grow the widest possible range of plants in ‘living collections’ and these highly managed environments may provide scope for growing an increased range of plants, as increased temperatures and the other key trends take effect. Botanic gardens are also in a key position to promote and spread knowledge on climate change and its effects.

In gardens more generally, plants are also grown in very favourable conditions:

• propagated in controlled conditions

• planted into carefully prepared ground

• protected from pests and diseases and competing plants

This should give us some optimism that the techniques and conditions for responding to climate change are already well developed and gives the garden an advantage over nature.

Though rather slow and insidious, it is already possible to detect some of these trends. The Central England Temperature Record shows that between 1750 and 1900 (150 years) the average temperature in Central England increased by 1 degree Fahrenheit (0.7 degree celsius). During the 20th century this trend advanced faster so that the average temperature rose by a further 1.5 degrees Fahrenheit with two thirds of this increase happening since the 1970’s.

This record also shows how 5 of the 6 warmest years since records began in 1659 occurred in the ten years 1989-99. The prevalence of frosts has also declined: an average of 55 frosty days in the 1880’s has reduced to about 35 days by the 1980’s. And closer to home, here in Norfolk, a local gardener has kept records of when certain plants started flowering in her garden from the 1960’s to the 2000’s. Mary Manning’s records show the advancing of Spring: Winter Aconites began flowering in mid January in the 1960’s and by 2000 this had moved to mid December. The same is true of Hazel, which first flowered around the beginning of February in the 1960’s and has likewise moved to before Christmas in forty years.

Global CO2 levels seem to be rising by about 1% per annum, though predictions of the future rate and impact of this inevitably vary according to assumptions about economic growth, reductions in carbon emissions and other factors. But although these underlying trends seem increasingly accepted, we also seem to be getting freak frosts, floods or droughts of varying length and intensity – almost at any time of the year, making the normal weather patterns of the seasons less and less ‘normal’.

Looking at the underlying trends, the impact of climate change on our gardens will most likely be determined by factors such as plant hardiness and tolerance of excessive wet, or drought conditions (see the chart for one forecast of reductions in water availability across the globe). This poses a challenge to the gardener’s ability to drain land or supply water as needed.

The British Meteorological Office points up some of the other potential impacts:

• ‘Increased carbon dioxide levels will increase rates of plant growth and perhaps development (bud burst, flowering and leaf fall)

• Changes in temperatures are expected to bring an earlier onset of growth in spring and a longer growing season

• Mild winters may reduce the yield of fruit trees, because colder temperatures are needed to break the buds

• Increased temperatures will aid the growth of more plants from warmer parts of the world

• Higher temperatures and decreased summer rainfall will cause stress, especially in plants with extensive, shallow, fibrous root systems

• Annual moisture content of soils is likely to decrease by 10-20% across the UK by the 2080s, with substantial reductions (of 20-50%) in soil moisture possible in the summer by the 2080s

• Fungal diseases will thrive with the wet winter conditions.’

So, as gardeners we have to cope with both the longer term trends (which arguably will not be very noticeable in the short term) and, perhaps more importantly, increased frequency of unpredictable, extreme weather events of uncertain length and impact. This ‘seasonal uncertainty’ is perhaps our greatest challenge as well as trying to use gardening practices which help to reduce CO2 emissions and are broadly sustainable.

Over the last four decades, extreme weather events have severely damaged many gardens and resulted in major economic losses. These events include:

• Severe winter weather in 1962/63 that killed many hardy plants

• Drought in 1976, which weakened trees and dried out lakes

• Storms in 1987 and 1990 that felled millions of trees

• Torrential and prolonged rain leading to soil erosion, flooding and drowning of plant roots in 2000, 2001, 2007, 2012 and now 2014

As Monty Don says,’The number one rule remains the same: do not fight nature’ (Gardener’s World Magazine, January 2013). He goes on to observe how ‘the past couple of years have been noticeable for the wrong weather most of the time’. We do not yet know if a new weather pattern (which is another way of saying climate or ‘average weather’) will establish itself , or whether we are in for ever more uncertainty. Or perhaps that’s just it – ‘the one certainty is that the weather will be more uncertain’ and we need to adapt our gardening techniques and habits to cope. As Monty says,

‘Expect the unexpected and be flexible’

So, lets look upon these new circumstances as a challenge to our gardening skills and respond to nature’s call. In my next post on climate change I’ll be looking at the advance measures we can take to better prepare our gardens for the unpredictable and longer term impact of climate change. If you have any direct experiences of climate change or any other comments I’d love to hear from you.

Further information:

Britain like Madeira?

My Climate Change Garden

UK Meteorological Office – impacts of climate change on horticulture

Royal Horticultural Society – gardening in a changing climate

‘Gardening in the Global Greenhouse ‘ – summary

Old School Gardener

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