Britain’s increasingly frequent deluges are rocking the environment and starting to change the way we see gardening. Horticulturists are having to think of ways to carry on growing plants that can cope with regular heavy rainfall; but the good news is, our plots could provide the solutions to mitigate flooding.
Storm Ciaran blew through just 10 days after Storm Babet, with both causing extensive water damage. After many people lost plants to the cold and wet during winter 2022/23, it looks like we’ll have to deal with the same thing in winter 2023/24, unless we start water- and weather-proofing our gardens.
What’s more, temperatures are heating up, with 2023 expected to be the hottest year on global record. Dr Freya Garry of the Met Office gave a list of scary statistics at a recent event organised by the Royal Horticultural Society on how both flooding and heat have hit the UK in recent years.
In July 2022 the first 40C UK temperatures were recorded. Since 1999, several months (February, April, June, November and December) have been the wettest on record. Six out of the 10 wettest years have occurred since 1998. Garry forecasts more severe and long-term droughts in the UK, too. She calls this weather rollercoaster a “boom and bust” cycle for gardens.
So, with global warming affecting the UK climate and hot and wet weather more prevalent, plants’ growing seasons are longer, which means that gardens are a strain on the water system. Hosepipe bans are becoming more frequent – a ban in Cornwall and Devon ended on September 25 after more than a year of restrictions – yet damp and warm winters lead to more plant diseases such as phytophthoras and mildews developing in British plants.
RHS environmental horticulture head Dr Mark Gush (he acknowledges the nominative determinism) says the annual growing season has increased by nearly a month in recent years, leading to more demand for more water over the summer, and says that water-saving ideas have four key themes: collecting rain, slowing flow, nurturing soil and planting the right plant in the right place. He particularly recommends mulching (using woodchip or bark) to protect soil from heavy rain.
RHS Wisley garden manager Sheila Das says water is often in the wrong place at the wrong time, so collecting this precious resource is important. She’s obsessed with water butts and has 5,000 litres’ worth in her garden. Hiding ugly butts with trees is her top tip – others include digging a pond to capture run-off and accepting that it will be full or empty, depending on the season. Retaining undulations in your garden, rather than flattening them out, is another idea, which provides places for water to pool instead of eroding your soil when there are downpours.
More plants in the garden will create healthy soil, which is “ultimately the best water butt we have”, adds Das. Soakaways (lined drainage ditches) in gardens are also useful for flood prevention.
Related to all this, the recent launch of next year’s Chelsea Flower Show revealed that weeds and rewilding are out and “resilient” plants for all weathers are in. Rising star Tom Massey is one of the Chelsea 2024 designers using water as a theme for their garden. He says his WaterAid garden addresses the climate crisis, which is, he says, “a water crisis”, as 90 per cent of all natural disasters are water-related.
“As our climate changes, water scarcity and insecurity will become more commonplace – here in the UK and around the world,” he says. “We can all do things to help mitigate climate change, such as improving soil health, planting greenery to provide shade, and, most importantly, managing water sustainably.”
His garden will capture all the rain that falls on it and will feature a rainwater-harvesting pavilion, which will filter and store water for drinking and irrigation, while also slowing rain flow. The planting will include water violet, which can indicate whether a water source is clean or polluted, and alder trees, which have nodules on their roots that can absorb nitrogen and toxic heavy metals from the ground, improving soil health and fertility.
How to make your garden weather-resilient
Ditch the fake grass
Tom Massey refuses to install fake grass for clients and loses work as a result. He thinks artificial lawns should be banned for new-builds because their microplastics leak into the soil, while rainwater may not if the sub-base is incorrect. The Society of Garden Designers is campaigning against “garden carpet”, which one in 10 UK gardens have.
Look for plants that can tolerate extremes
Grower Mark Straver of Hampshire nursery Hortus Loci, which is supplying several Chelsea 2024 gardens with trees and plants, says resilient plants – not those that are only resistant to flood, drought or heat – are essential for the future. Plants need to tolerate -20C and +40C, as well as storms; he says warmer climate plants such as phormiums were “killed stone dead” in the UK by frosts in December 2022.
Garden designer Ann-Marie Powell, who will also design a show garden at Chelsea next year, says Celtis sinensis (Chinese hackberry) and Maackia amurensis will be key trees in her garden, which will include bright and exuberant planting with colourful woodland edges, and shade and marginal bog plants which can survive rising and falling water levels.
She believes the hackberry and Maackia are “trees for the future” because they tolerate extremes.
If your garden is prone to flooding, plan ahead
RHS chief horticulturist Guy Barter says raised beds drain better than conventional flower beds in terms of stopping your plants from drowning in the mud this winter; although he adds that there’s “nothing much you can do” to combat heavy rain other than plant resiliently: you can water in drought, but it isn’t possible to take water off a sodden garden.
Somerset grower Dave Root of Kelways is supplying several Chelsea gardens, and his tips for wet-loving plants include Iris sibirica, which forms substantial clumps, and the moisture-loving primulas, japonica and bulleyana, which have contractile roots that are particularly suited to areas that flood.
Closer to the coalface of the ordinary gardener, Matt Peck of Leicestershire-based Gates Garden Centre says cornus and cotoneaster are best for boggy areas.
The more naturalistic your garden, the better
A UN water summit in September showed that rebuilding vegetation is the best way to slow the flow of water. Dr Mike Maunder, executive director of the Cambridge Conservation Initiative, said that “de-paving” your garden will help to create more permeable surfaces for water to drain away. He also pointed out that the greener the lawn, the more chemicals you have put in it (and the less chance other vegetation has to grow), so the yellower the better in the summer.
One long-term plan to stop the deluge from hitting too hard is to plant trees, which mitigate flooding through their root networks, while their canopies slow the rain’s path onto the ground.
Plant trees before Christmas is former Kew arboretum head Tony Kirkham’s tip, so they establish before spring. He says resilient trees include Indian horse chestnut, Sorbus Olympic Flame, acers, malus and betula.
RHS Bridgewater curator Marcus Chilton-Jones recommends the liquidambar for long and wet winters.
Protect your soil
Planting green manure cover crops such as winter field bean or tares can help to stop soil washing away, and practising no-dig gardening is a good way to retain soil structure so that your plot doesn’t look like Glastonbury in a wet year. Whatever happens, extreme weather is going to become more common, so we need to look differently at how we garden.