The impacts of climate change on gardening around the world are becoming clearer, though of late perhaps the emphasis has shifted away from global warming, the associated changes in the onset and duration of the seasons and the conditions for growing different plants. The recent focus has been on prolonged extreme weather events like peristent wind and rain in the UK, drought in pacific north America and ice and snow in the mid west and eastern seaboards.

In this second of a series on climate change and gardening I’ll set out a few ideas for ‘being prepared for the unpredictable’.

I originally wrote this article in March 2013, whilst looking out on a sunny but cold day – temperatures were hovering around freezing and a biting easterly wind reduced the temperature feel by a few more degrees. The ground was cold, spring flowers were struggling to make headway and some of my seedlings were battling to stay alive, let alone get to the potting up stage!

Once again, this year in my part of the UK (central Norfolk), we seem to have escaped the worst of the most recent bout of severe weather. Elsewhere in the country where there was deep snow on the ground last year (some drifts were over 4 metres deep and there was talk in the press of ‘the coldest March for fifty years’ and ‘the longest winter since 1962’), this year, as Spring knocks on the door, we’ve had a relatively mild winter, but one which has brought severe flooding, wind and other storm-related damage (such as ‘sink holes’) to many parts of the UK.

Professor Sir John Beddington

As the retiring UK Chief Scientific Advisor, Professor John Beddington warned in an interview last year:

“The [current] variation we are seeing in temperature or rainfall is double the rate of the average. That suggests that we are going to have more droughts, we are going to have more floods, we are going to have more sea surges and we are going to have more storms…These are the sort of changes that are going to affect us in quite a short timescale”

So, it looks like many (if not most) gardeners face the challenge of seasons tipping between unusual weather patterns including long periods of drought, flood and frost.

Wild flower meadows can be a more sustainable option than frequently mown lawns.

My first article in this series about climate change and gardening looked at what the forecasts said, based largely on models of climate change produced about ten years ago. Last year the Royal Horticultural Society and University of Reading linked up to publish a new research report  which is based on new forecasting models and which includes the results of a survey of gardeners on what they perceive to be happening and what measures they have already taken or are preparing to take. This survey revealed that two-thirds (62%) of British gardeners feel optimistic that they can adapt to the challenges climate change may bring, while 70% believe changes in gardening practices can help them garden successfully in a changing environment.

So, we all know that in the short term we can do certain things to avoid the worst excesses of the weather and I’ll be reviewing these in my next article. In this post I want to set out a few ideas for some more strategic measures we might take to ameliorate the impact of abnormal weather events.

So, what are we trying to achieve?

It might sound obvious, but I guess we’re trying to create the right growing conditions for the plants that stand a good chance of growing (if not flourishing) in what are the underlying climatic conditions for where we live. 

In the UK, ‘maritime climate’ is a disarmingly simple term which refers to what can, at the best of times, mean very variable weather conditions from region to region and from month to month. Overlay the effects of climate change on this and the (unexpected) variability can be that much greater. We need to look at ways of managing and manipulating the ingredients for growing success – or if you like, putting in place measures that can maintain the right ‘micro climate’.

This is nothing new. The Romans harvested winter rains for use in their parched summer gardens. The ancient Tiwanaku people of South America developed an ability to manage the growing environment for their crops. They lived between Lake Titicaca and dry highlands in present – day Bolivia. The area near the lake provided key resources of fish, wild birds, plants, and herding grounds for llamas. Further to the east in the Altiplano area is a very dry, arid land. Here, the high altitude Titicaca Basin provided less promising growing conditions and resulted in the development of a distinctive farming technique known as ‘flooded raised field’ agriculture (suka kollus).

tiwanaku raised field system

Aerial view of raised field system

This consists of artificially raised planting mounds separated by shallow canals filled with water. The canals supply moisture for growing crops, but they also absorb heat from solar radiation during the day. This heat is gradually emitted during the bitterly cold, frosty nights, providing ‘thermal insulation’.  Over time, the canals were also used to farm edible fish, and the resulting canal sludge was dredged for fertilizer. The fields grew to cover nearly the entire surface of the lake and although they were not uniform in size or shape, all had the same primary function. Though labour-intensive, suka kollus produce impressive yields. Significantly, experimental fields recreated in the 1980s by Alan Kolata and Oswaldo Rivera of the University of Chicago suffered only a 10% decrease in production following a 1988 freeze that killed 70-90% of the rest of the region’s production.

So, as we can see, the Tiwanaku engineered fields that were specialised in coping with seasonal variations and were able to ameliorate otherwise frosty local conditions. It is this sort of approach – ‘working with nature’  rather than attempting to control it – that is the key to coping with the impacts of abnormal weather events in our gardens.

What can we do to get our gardens prepared for climate change?

Home made compost – try to create as much as possible to improve soil structure and fertility

Soil

• Organise home composting and leaf mould creation, if at all possible. Organic matter added to all types of  soils will improve water absorption, aeration and fertility. Double (deeply) dug beds with plenty of organic material incorporated will be a great help. Likewise adding gravel to heavy soils can help to loosen up the structure.

• Add mulches of organic materials to beds to help conserve moisture or otherwise use ‘cover crops’ to avoid areas of bare earth which will dry out more quickly.

• Raised beds will provide well – drained growing conditions  and an annual layer of organic material may be all that’s needed to keep the structure and fertility up to scratch (and can be extended further with alternating layers of different materials such as newspaper to keep weeds down and improve structure and moisture retention when needed – so called ‘Lasagne gardening’).

• Make sure you adopt ‘healthy practices’ when preparing growing media and containers so that you minimise the risk of harmful diseases – wash out pots and seed trays. And remove all those little potatoes from a plot where you grew these to avoid encouraging blight.

Rain gardens can provide a solution to gardens with excess water

Water

• Don’t pave over large areas of open ground for parking, patios or other reasons, unless the materials used are permeable to allow run off. Likewise use permeable materials for paths such as gravel, bark chippings or in combination with pavers and/or ensure runoff into surrounding beds and borders if the ground can take the surge of heavy rainfall.

• Could your garden (or perhaps an area of lawn) benefit from improved drainage? Apart from installing a system underground, you can improve aeration and absorption in lawns by annual spiking with a fork (or if the area is large a mechanised version of this) plus scarifying the surface with a spring rake. Better still, reduce the area of lawn or remove it altogether – in  some areas people have replaced even front garden lawns with food growing beds.

• For temporary flood protection, try ditching the boundaries of your plot to hold and possibly divert excess water to places where it can be better coped with – for instance you could create a pond or pool to capture excess water and possibly also provide a ready source in times of drought and help to attract beneficial wildlife to help control pests. And think of the Tiwanaku and their frost preventing raised field planting – creating bodies of water near frost pockets can help to reduce the impact of cold weather.

• Look for opportunities to use excess water to add new planting areas to your garden – bog or rain gardens where planting can be adjusted to make use of the wetter ground conditions. See this link for further ideas on storm water management.

• And alongside this have water harvesting measures in place to capture rainwater so that it can be stored and used when needed – barrels, butts or tanks fed from downpipes – even underground storage tanks are now available.

• Consider using weeping hoses, automatic irrigation systems or simple measures like short lengths of pipe/open ended plastic bottles inserted in the ground alongside plants to ensure watering is efficient, reaching the roots rather than evaporating on the surface.

Efficient watering can be simple

Make your own greenhouse from recycled plastic bottles

Temperature

• Think about the mix of planting you have and if hot weather is likely to be an issue, ensure that shorter, smaller, more sensitive plants are sheltered at the hottest time of the day by some shade from other overhanging trees, shrubs or other planting.

• Likewise, more permanent structures such as pergolas, arbours and the like can provide not only an interesting growing feature but can provide shade for plants underneath or along their edges.

• Greenhouses, polytunnels, conservatories and even light rooms in the house (where temperature and humidity can be controlled) can provide a protected environment for over – wintering plants that would otherwise perish in cold spells. Heating your greenhouse adds greater flexibility, and can be ‘green’ if you harness the earth’s thermal energy through some sort of simple heat exchanger that taps warmth below ground.

• Use cloches, larger plant covers or cold frames to provide mini controlled environments which can enable germination of seeds, development of seedlings and possibly protection of less than hardy plants during times of frost or prolonged cold. The growing season (especially for food crops) can effectively be extended through such methods. See this video for information.

Wind breaks can reduce the impact of strong winds

Planting

• Use wind breaks of trees, hedges, other planting or permeable barriers of suitable man-made material fixed to posts to reduce the speed and force of winds which can cause dessication (drying out) of plants  as well as structural damage. These measures can be used on the boundaries of the garden as well as inside it to create pockets of  still air which can also raise temperatures.

• Choose plants which can cope better with weather extremes; look out for indicators of resilience on plant labels and especially accreditations such as the RHS ‘Award of Garden Merit’ (AGM- I’ll be covering this in more detail in my final article of the series).

• Plant for the future, using trees, shrubs and hedges that are drought tolerant or damp-loving – whatever is suited to the conditions in your garden or parts of it.

• Avoid long-term planting in flood areas, unless you are trying to create different growing conditions like bog or rain gardens.

• Avoid clearing slopes of vegetation as this may cause erosion problems.

• Encourage biodiversity and beneficial wildlife through your choice of plants (as well as the other measures that you can take to create different habitats) so as to help control unwanted pests. Planting a native species hedge for example can encourage wildlife and provide shelter from drying winds or storms.

• Think about increasing the proportion of perennials you grow, including fruit and vegetables, as these are less demanding of fertility and CO2 emission in their propagation etc.

A garden pond can help with capturing excess water and improve biodiversity

And finally, think sustainably when considering the overall impact your garden and gardening practices will have on the world. Gardens are enormously valuable in the fight to reduce CO2 emissions and by reducing or removing the use of powered tools (especially those used in lawn maintenance) we can further increase the beneficial impact we have.

In my next article in this series I’ll turn my attention to gardening techniques and short term measures we can take to manage the impact of abnormal weather patterns. In the meantime, if you have any direct experiences of climate change or any other comments I’d love to hear from you.

Other articles in this series:

Four Seasons in One Day (1): Climate change and the garden

Further information:

Wikipedia- Tiwanaku

Sir John Beddington’s warnings on climate change

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

RSPB- guide to sustainable drainage systems (download)

RHS guide to front gardens and parking

Old School Gardener

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