The £10 mineral that could make your garden as green as Wimbledon's courts

A naturally occuring crystal found far beneath the North York Moors can help make grass grow faster and stay healthy

It is the world’s oldest and most famous lawn tennis tournament, so it is no surprise that Wimbledon pulls out all the stops to keep its grass immaculate.

But achieving a garden as vivid green as the courts of the All England Club is not as impossible as one may believe, as its secret ingredient - a rare mineral salt mined beneath the Yorkshire Moors - can be bought for just £10.

Polyhalite is a naturally occurring crystal made up of four nutrients - potassium, calcium, magnesium and sulphate - which experts say can help to make grass and other crops grow faster and stay healthy when used alongside other fertilisers.

Not only does it allow Wimbledon’s groundsmen to use less chemical nutrients in line with its sustainability goals, it may also be responsible for the intense colour of the club’s courts.

Karen Hudson-Edwards, a professor in sustainable mining at the University of Exeter, says this is because of the presence of magnesium in the mineral salt.

“The green colour of grass is due to the presence of chlorophyll,” she told The Telegraph. “This absorbs the red and blue wavelengths of light and reflects green at the same time, giving grass its green colour.

“The magnesium that can be added to grass through products such as polyhalite promotes production of chlorophyll.”

Currently, the only polyhalite mined in the world comes from the Boulby Mine in the UK, from a layer of rock over 3,300ft below North Yorkshire and extending off the North Sea coast.

Dr Forest, a fertiliser company, sells bags of extra fine organic polyhalite fertiliser on eBay for £10 for 750g; £15 for 1.5kg; and £43 for a large 9kg bag.

Ed Conway, an author who has ventured to the depths of the mine as part of his research, said the significance of this “magic material” goes far beyond the grounds of the All England Club.

He said that the “word is spreading” about the mineral, and believes that although it will not replace other fertilisers - traditionally composed of nitrogen, potassium, or phosphates - it could help alongside them.

“And this is part of the answer for how they make the courts at Wimbledon so green and beautiful,” he said.

Prof Hudson Edwards agrees that polyhalite is growing in popularity among gardeners and corporations as an alternative fertiliser, possibly because of its green credentials.

“Compared to other fertilisers, it is more environmentally friendly,” she said. “After it is mined and crushed for use, it does not undergo any further processing that might require environmentally unfriendly chemicals.

“Also, the polysulphate in polyhalite is approved for organic agriculture and is Soil Association certified, meaning that its use will be associated with lower carbon emissions than other polysulfates that are not approved.”