‘We can’t rely on April showers any more’

How to future-proof British gardens in the face of a looming water crisis – Garden Water Scientist, Janet Manning and Head of Environmental Horticulture, Mark Gush explain

Nature Target 4 of the RHS Sustainability Strategy: Water Neutral by 2030

To use less, capture, reuse and recycle water in RHS operations including gardens and shows and to encourage water neutral gardening practices

What does this target mean?

‘Our climate is changing, and fast. That’s throwing up all sorts of challenges for gardeners, especially in the way we think about water. An increase in both droughts and flooding means that water will matter much more to us all in future.

‘We’re all accustomed to the concept of food miles, but what about water miles? Every drop that enters or leaves gardens in a mains pipe (tap water and waste water) must travel, and carries with it an environmental cost. And climate change is making that cost ever more prohibitive.

‘Going water neutral is all about minimising inputs and outputs. That means using less mains water, watering efficiently, and also creating less waste water.’

What is the RHS already doing to meet this target?

‘All the RHS gardens already have water-saving measures in place. For example, at Hyde Hall in Essex, they created a several million litre reservoir to catch and store excess rainfall – it’s big enough to ensure the garden doesn’t need to use mains water on its plants, ever!

‘At RHS Garden Bridgewater they’re making use of SUDS [Sustainable Urban Drainage Systems] to store stormwater, which helps prevent flooding locally and provides irrigation in dry periods. Rainwater harvesting from the Plant Centre roof also contributes to the garden’s ‘water budget’. At Rosemoor in Devon, the garden’s lake is truly multipurpose, providing irrigation water, stormwater storage and an ornamental feature in its own right. 

‘At the new Wisley Hilltop building there is an underground rainwater storage system (called Permavoid) which captures and stores rainfall from the roof of the building and then gradually supplies that water to the soil and plants growing above it. It uses a wicking system that draws the water up into the soil by capillary action – these are just a few examples of our organisation-wide commitment to saving water.’

What will the RHS do next to meet this target?

‘Our focus will be to raise the profile of water as a critical and “at risk” horticultural commodity, within and beyond the RHS.

‘The first part of our approach will be to further refine our baseline water use, by enhancing metering, monitoring & analysis of water data. Then we’ll work out our site water balances (inflows / supply, outflows / demand).

‘The next step will be to reduce our water use, by eliminating leaks and wastage, switching from mains to rains supply and implement water use efficiency measures, along with reusing and recycling water.

‘We’ll also aim to replenish supplies by harvesting and storing as much water as possible. “Do no harm” is an important principle too - this means thinking about the bigger picture of where water comes from and where it goes. In practice this is everything from applying lawn fertiliser correctly so it doesn’t get washed off in heavy rain to pollute nearby rivers to installing permeable paving or planting wherever possible to help prevent flooding.

‘We are planning to make water an integral factor in every piece of infrastructure we create, at every stage of planning, design and implementation. For example, the latest plans for RHS Wisley include a reservoir big enough to hold 10% of the site’s water demand, all from natural sources.'

[Janet] ‘I’m creating a “water roadmap” for RHS Garden Wisley, which will be a potential blueprint for other RHS sites. It assesses current water usage, projected usage, sources available, whether there’s any gap between supply and demand, and what we can do to plug the gaps.

‘The RHS will increasingly implement rainwater harvesting, storage and recycling across all RHS sites and Flower Shows.’

The way we garden will change dramatically over the next decade. We'll need to be more flexible and adaptable in the face of a fast-changing climate

Janet Manning, RHS Water Scientist

Why should gardeners care about this?

‘If you want to get a picture of the challenges that gardeners are facing, just look at the Met Office’s report, State of the Climate 2021. Records just keep getting broken. For example, the year 2020 alone broke three weather records, and even though overall it was wetter than average we still had a prolonged spring drought! 

‘We really can't rely on April showers any more – we will need to be more flexible and adaptable in the face of a fast-changing climate. The way we garden will have to change dramatically over the next decade.

‘Climate scientists have been predicting an increase in extreme weather events for a while, and now they’re unfolding before our eyes. Gardens and gardeners across the land are facing new challenges, including droughts and flooding in areas that were previously unaffected. Parts of the country are facing an ongoing, sustained water shortage that is only going to get worse.’

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