On a dank day in January, a small slice of Walsall is blooming. Marie and Tony Newton’s back garden is filled with summery colour: miniature mauve cyclamens, frilly red camellias, graceful hellebores, seasonal snowdrops and the bright green sheaths of bulbs promising more flowers to come. A few winters back, their first daffodil bloomed on Boxing Day.

“It’s basically chaotic,” says Tony of the new climatic normal. “It’s non-stop flowers from now on. Winters are milder on average and there’s every opportunity to have a riot of lovely flowers from December right through till spring.”

Deadly floods in Bangladesh, devastating wildfires in California, melting glaciers in Greenland, coral bleaching in the oceans – this is climate change in action. Highlighting far more benign changes in Britain, long blessed with a moderate climate, may appear trivial or downright insensitive. Our gentle extremes – the beast from the east, or summer 2018 being England’s hottest ever – are far from drastic. But they still pose challenges, and there is more change coming.

Britain’s 27 million gardeners could be the canaries in our coalmine. How are gardeners experiencing climate change in Britain and how is it transforming our gardens? And can adapting our gardening styles mitigate the negative impacts of climate change?

Marie and Tony couldn’t see their garden when they first viewed the house in 1982 because it was covered by a snowdrift. In the years since, as their south-facing quarter-acre evolved from a children’s play-space to a “four-seasons garden” with an all-year-round rainbow of flowers, shrubs and trees, they have witnessed the Midlands climate become steadily milder. Autumn frosts are much later, if they strike at all, and September is a summer month now. Their begonias continue until October. “That would never have happened in the past; we’d barely get through September without air frosts,” says Tony. “Although it’s warming up, you’ve got to plan for the extremes. We’re still going to get very severe winters and it will wipe out many gardeners’ new species.”

They know about this only too well. Their garden features a jungle area of bamboo, palm trees, a banana tree and the stumps of several Tasmanian tree ferns. These ferns survived the winter of 2009, the coldest for 30 years, but a run of -15C nights and sub-zero days the following December killed them off. “It’s a mortgage to replace them,” grimaces Marie. Climate change is encouraging many gardeners to buy exotic plants but “we still need truly hardy varieties,” says Tony. Their banana is wrapped in black cloth over winter. He ensures that whenever they add a shrub to the 3,000 in their garden it can survive at -15C.

Marie and Tony’s garden fared better during last summer’s drought. Their clay soils retain moisture, which helps, but they didn’t lose a single plant to the weather, despite being on holiday for two weeks. This may be because they are obsessive mulchers. Mulch is material added to the surface of the soil to increase organic matter and repress weeds. The Newtons have added 108 cubic metres of tree bark to their soil over the years; each year they also compost all their garden leaves and cuttings, reapplying this to their soil. This organic matter has steadily improved soil quality and, crucially, helps it retain moisture.

When Liam Shoesmith, deputy parks manager of Truro city council, saw how dry 2018 summer’s long-term forecast looked, he suggested the city’s gardeners should plant succulents and cacti for their Britain in Bloom competition entry. “It was a bit of a joke really,” he says. But the community group that organises Truro’s displays took his advice. In what the Royal Horticultural Society (RHS) described as the “toughest year for community gardening in 54 years”, Truro’s blend of exotic, drought-tolerant plants, including palms and Mediterranean herbs, serviced by a solar-powered rainwater-harvesting system, thrived. And Truro won the Britain in Bloom competition for the first time.

Shoesmith is currently dispatching his team to mow parkland grass: milder winters mean Truro’s grass grows all year round. He began gardening as a boy in the 1980s. “It’s definitely milder and wetter,” he says. “The difficult thing we have with the climate is the more changeable weather. Last winter was probably one of the wettest on record here and then we went into one of the driest summers. The capricious nature of the weather is very hard to anticipate and work with.”

We don’t think of mild winters as extreme weather events, but December 2015 was the most anomalous month ever recorded, 5.1C above average, and the warmest in the Met Office’s central England temperature dataset, which stretches back to 1659. Shoesmith notices how pollinating insects, such as solitary bees, often emerge during these mild midwinters. If there are no flowers, and no nectar, they will perish. “Climate change is a big issue and as gardeners we can all do our bit to help by planting the garden so it’s flowering throughout the year,” he says. “We all want that anyway.”

Wildlife-friendly gardening focuses on native flowers, but Shoesmith argues we have long had non-native plants – particularly in milder Cornwall – and many exotic species are just as attractive to pollinators. In general, Britain’s 400,000 garden plant species provide genetic diversity, enabling more selection and breeding to adapt to future extremes. But Shoesmith also has a motto – “don’t go silly buying too much frilly” – because certain varieties of exotic flowers with lots of petals lose their nectar-holding sexual organs and so become useless for pollinators. Daisies, aconites, crocus, hellebores are good for winter-waking bees.

Allotment holders are also adapting to the increasingly capricious climate. Mandy Barber has turned to growing perennial produce on her plot in Ashburton, Devon. “Annual vegetables needed a lot more watering and it was touch and go whether they would make it last summer, but perennial vegetables have a lot more resilience to temperature changes,” she says. Barber is experimenting with crops including Taunton Deane kale; poireau perpétuel, a perennial leek; and Hablitzia tamnoides, or Caucasian spinach, which is grown in Scandinavia and can survive -25C. “The Hablitzia tamnoides plants go on for decades, they are like a rampant triffid, but you get a crop between February and June every year and the leaves are a bit like baby spinach,” says Barber. She also propagates and sells these perennials.

Facebook Twitter Pinterest Part of Truro’s winning entry to the Britain in Bloom competition. Photograph: Jim Wileman/RHS

Every gardener I speak to agrees that milder winters are enabling more pests to survive and encouraging new pest species. Allan Trigg has been growing vegetables for more than 40 years and has an allotment in Chelmsford, Essex. “This is my little patch of England,” he smiles. Fewer frosts means his fellow allotment holders plant out runner beans, sweetcorn and potatoes earlier. With an extended growing season, Trigg can grow more, and second crops, although last year he grew less because he was spending so much time watering his vegetables. The dry weather produced lower yields of crops such as potatoes. After 2017, his potatoes lasted him and his wife through to February; this winter, they were eaten by November. And allium leaf miner and leek moth are a growing problem. “I used to grow loads of leeks but now I don’t bother,” he says. He pulls one up to show the damage below ground. “We never used to have this trouble years ago.”

In Walsall the Newtons are accepting of their growing losses to pests such as the lily beetle and the lace bug. “It went absolutely berserk after the hot summer,” says Tony. “I thought it was going to kill all the plants in the garden.” Barber is beset by voles (which survive the milder winters), while in Cornwall, Shoesmith has noticed the spread of fuchsia gall mite along the hedges. “It had the opportunity to come to Britain for decades, but only arrived this century because of the milder winters,” he says. “We don’t have the same amount of frosts now and so we get many more fungal problems.”

These observations precisely match the more scientific language of Gardening in a Changing Climate, a 2017 RHS report that outlines the challenges – milder winters, more unpredictable extremes and more pests – posed by climate change. But the RHS also asks how gardeners might help save the planet. The way we garden is still sometimes part of the problem – using precious water in pursuit of a perfect lawn during a drought springs to mind – but it can be part of the solution. Gardeners can reduce carbon dioxide emissions, mitigate pollution and flooding, and help increase their neighbourhood’s resilience.

“Water use in gardens is going to be a major issue in the future,” says Alistair Griffith, director of science at the RHS. London is forecast to require 100m litres a day more than it can supply in 2020, with this deficit rising to 400m litres a day by 2040. The use of energy-intensive mains water on gardens is still socially acceptable and Britain lags behind more water-stressed countries where grey-water recycling is commonplace. But hosepipe bans could become perpetual for some regions in coming decades.

Apart from using only rainwater – even a small balcony can catch and store rainwater with a mini-reservoir – Griffith recommends gardeners provide “as much greenery as possible”. He suggests planting hedges instead of fencing and planting trees. Trees not only dispel pollution but can alleviate flash flooding and provide shade for a home during heatwaves. Perhaps the most overlooked way gardening can benefit the climate is via the soil: adding organic matter (mulch from home-composting, not peat) can create a soil that stores more carbon and retains more water, also making gardens more resilient in flood and droughts.

Griffith’s final practical suggestion for climate-friendly gardening is to make everything permeable. Unfortunately, paving gardens for parking continues (in 2015, the RHS found that the number of paved, plant-free front gardens had tripled in 10 years from 1.5m to 4.6m). Even car park gardens can be permeable and planted with trees and shrubs around the edge. But, according to Griffith, people resist, citing a lack of time and a nervousness about failing at gardening. “Gardening is always trial and error,” he says. “Give it a go.”

Gardening won’t stop climate change, but it could make our local communities more resilient when faced with extreme floods, heat – and mild weather. In troubled times, it is also a fundamentally optimistic gesture.