IT’S not easy being a grape during a scorching Californian summer. But a renowned wine-maker in Napa Valley has come up with an unusual — and surprisingly effective — way to stop his cherished fruit from withering on the vine: he sprays it with sunscreen.

This may conjure up odd images of grapes lounging on deckchairs, reading airport novels, but the solution has worked.

The Californian grapes, like the starlets in Hollywood who use factor-35 moisturiser and spray-on tans, have remained wrinkle-free.

Farmers are now wondering whether a healthy slathering of sun-block could protect other crops from global warming, in particular tomatoes, which are notoriously sensitive to hot weather.

Aaron Pott, winemaker at the Quintessa vineyard, argues that his wrinkle-free grapes are proof that the sunscreen works. Whether the critics agree is another matter. However, Quintessa’s blend of cabernet sauvignon, merlot and cabernet franc, which is aged in French oak barrels in caves dug into the Napa hillside, is highly regarded, usually scoring more than 90 points from Wine Spectator magazine and costing up to $200 a bottle in restaurants.

“The grapes for cabernet sauvignon face the same summer sun exposure dangers that concern bikini-clad sun bathers,” Mr Pott said. “We’re all aware of the benefits of aloe vera in protecting ourselves from sun damage. We simply took that evidence into the vineyard.”

Not that grape sunscreen is exactly the same as human sunscreen. In winemaking terms, it is a compost spray that includes small amounts of aloe vera and yucca, ingredients shared with human sun treatments.

Mr Pott, a graduate of the University of Burgundy, who has previously worked on wine estates in Bordeaux and Chile, uses other techniques that should also be familiar to the pale-skinned British holidaymaker. He manages the growth of leaves on the vine so that they provide a natural canopy of shade for the grapes, and also sprays them with a mist of cool water at critical times.

All this is part of an agricultural technique known as biodynamics, which rejects the use of artificial pesticides, herbicides and fertilisers. It was pioneered in the 1920s by the Austrian philosopher Rudolf Steiner, predateding both the organic farming movement and concern over climate change.

Central to biodynamics is the theory that you make sprays, or “teas”, from plants with certain qualities, such as drought resistance, and then use these sprays on other plants to give them the same protection.

Mr Pott uses about two to three ounces of yucca per acre, and about four to five ounces of aloe vera gel per acre, each mixed in with a compost spray.

Because the spray is so diluted, there is no residue by the time the grapes are picked. As for the taste of the world’s first sunscreen grape, connoisseurs will have to wait longer than usual to satisfy their curiosity: the 120F (48C) heat of the summer (48C) has delayed the harvest for several weeks.

Mr Potts, however, is confident. “We’re really just hitting the tip of the iceberg with these kind of treatments.”

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