Slug-free lettuce leaves a bitter taste

THE RHS may have found the secret to getting slugs and snails to leave your lettuce alone – but it comes with a catch.

A study by the gardening charity testing popular calcium deterrents found that unfertilised lettuce was much less palatable to the gastropods, but also less delicious for humans.

Emma Thornton, a summer student, examined two brands of calcium deterrent, designed to make crops less attractive to slugs and snails, in the first independent study to test whether the products work.

Calcium products, which often come in liquid or spray form, are a treatment added to the plants every two weeks to deter garden visitors from having them for dinner.

Lettuce treated with these products and a fertiliser was tested alongside crops fed just with fertiliser, and lettuce left alone without fertiliser or treatment at all.

Leaves were left with grey field slugs, brown soil slugs, threeband slugs and the common garden snail, to see which type they preferred.

Calcium sprays are designed to be a humane, eco-friendly alternative to lethal methods that kill the slugs and can also harm birds and other wildlife.

But the study found no difference between plants doused with the calcium feed or a normal fertiliser.

The leaves that fared the best were fed with no fertiliser at all, though the RHS does not recommend this method. The unfertilised lettuce was small, tough and bitter, making it less attractive to both people and slugs – negating the point of growing the lettuce.

Hayley Jones, who leads the RHS’s research on slugs and snails, said: “Slugs didn’t like it, but people wouldn’t like it either, so it’s unfortunately not a solution.”

Further test are planned using different plants and applying the calcium products more frequently to see if that makes it more effective.