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RHS tree trial to help gardeners better weather climate change
by RHS
June 1, 2021

A new five year study led by the Royal Horticultural Society (RHS) in partnership with Frank P. Matthews nursery, is to advise gardeners on the best varieties of tree to weather climate change.

With the UK expected to see wetter winters and warmer summers the RHS’ tree scientist will analyse the extent to which ten varieties of garden tree can help counter flooding and aid cooling in urban areas while also capturing carbon.

A total of 60 trees have been planted at RHS Garden Wisley’s John McLeod Field Research Facility and connected to sap flow sensors and soil moisture probes. Leaf area, stem growth and photosynthetic rate will be among the traits measured on a regular basis. Combined with local weather data, these readings will provide an analysis of each tree’s water storage and use and air cooling capacity.

The RHS will be putting to the test existing research which suggests that trees with a larger leaf area retain more water in their canopy and ‘thirstier’ plants are more productive at cooling and in preventing runoff and flooding. The study will also identify other tree characteristics that are desirable in providing ecosystem services.

The ten species of tree being analysed are: Blue Spruce ‘Erich Frahm’, Callery pear ‘Chanticleer’, Flowering cherry ‘Shirofugen’, Ornamental hawthorn ‘Prunifolia Splendens’, Crab apple ‘Scarlett’, Dawn Redwood ‘Goldrush’, Holly ‘J C val Tol’, Magnolia ‘Rich Pink’, Rowan ‘Olympic Flame’ and Cypress ‘Garda’.

Early findings will be made available next year, including as a talk and interactive display at RHS Hilltop, a new state of the art science facility at RHS Garden Wisley that opens to the public on 24th June. For more information visit www.rhs.org.uk/hilltop.

Elisabeth Larsen, tree scientist at the RHS, says: “Gardeners have the power to improve their local environment by making informed planting choices. Aesthetics often play a role in decision making but even more so people are looking for guidance on what plants can help them overcome issues such as pollution, noise and temperature. More than half of all UK gardens are thought to have at least one tree – that’s 11 million trees - and so understanding which can help alleviate two of the most pressing seasonal problems could stand to make a huge difference over the coming years”.

The RHS advisory team has reported a growing number of enquiries related to the ecosystem services of plants and recent research on hedges advises gardeners which to grow for noise attenuation, pollution capture and wildlife.

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