Dig trenches to save thirsty plants and prevent flooding, gardeners advised

The Royal Horticultural Society has advised gardeners to dig trenches around their plants to capture rainwater during this week's thunderstorms to avoid flooding.

The RHS said that “digging out a hollow, dip, or even just a dish-like shallow ring” would help trap water around thirsty plants and give the dry soil time to absorb it.

“With the ground baked hard after two months of near-drought, heavy downpours could result in significant runoff which may not reach plants and could result in localised flooding,” the society said.

The advice came as the Met Office placed much of the UK under yellow thunderstorm warnings. Scotland and Northern Ireland were put on alert from noon on Sunday with much of England and Wales joining them from Monday morning.

“The warnings highlight the chance of some places seeing around 50mm of rain falling in a three-hour period in the north, with some areas further south possibly seeing around 30mm of rain in a three-hour period. Hail and frequent lightning are also possible as part of these downpours and represent an additional hazard,” said Jason Kelly, the Met Office’s deputy chief meteorologist

Despite the storms, experts warned that the heavy rain was not the type needed to bring much relief from the drought.

Soils hardened by weeks without rain and baking hot temperatures will struggle to absorb the intense and sudden downpours brought by the thunderstorms. Instead, torrents of water are likely to simply run off the parched soil, potentially contributing to flash floods.

The ‘wrong’ kind of rain

Simon King, a BBC weather presenter and meteorologist, said it was the “wrong” kind of rain.

“The ‘right’ kind of rain we need is from the more persistent and steady type. This gives the parched ground more time to soak up the rainfall before it disappears into the nearest drain or river,” he said.

“The ground has effectively become like urban concrete,” Robert Thompson, a professor of Meteorology at the University of Reading, told the BBC.

The professor had earlier posted a popular video to social media showing how slowly dried-out ground absorbs water compared to normal soil. While a wet lawn absorbed an inverted cup of water in seconds and the grass after a normal summer took less than a minute to do so, the cup placed on heatwave-baked soil barely drained at all.

Despite the sudden shift in the weather, the Environment Agency added its voice to warnings that the drought is likely to last into next year.

John Curtin, executive director for local operations for the agency said drought “will probably be an issue for months ahead depending how the winter goes”.

“We’ve lost a week’s worth of rain and it’ll take weeks of rain, we’ll need probably average or slightly above average rainfall this autumn into this winter for us to not be in a drought next year.”

Parts of the country have experienced the driest July since records began in 1836, while last month multiple parts of the country breached the 40 degree celsius mark for the first time ever.

As well as advising gardeners to dig trenches around plants in need, the RHS also said they should spike lawns to allow them to better absorb water, pushing 10cm deep every 10-15cm with a pitchfork, and install water butts to future-proof against Britain’s changing weather.

A two-by-three-metre shed could fill up to 18,  210-litre water butts in an average year of rain in southern England, the society claimed.

It also called for the public to ditch hard surfaces in their gardens and plant shrubs, trees and hedges to help reduce flooding.

“This summer has undoubtedly proved an endurance test for plants and the 30 million gardeners who tend to them. It will no doubt influence what we will see planted in our gardens and communities and the ways in which plots are managed in the future” said Leigh Hunt, principal advisor at the RHS.