Anyone who has struggled during this year's seemingly endless torrential rain to grow lettuces or cabbages without their crops being obliterated by slugs and snails will have tried every method they can think of to protect their plants. But experts have warned that gardeners who use coffee grounds – one of the more popular organic alternatives to slug pellets – as a deterrent are doing so in contravention of EU regulations. The Royal Horticultural Society has published the warning in the latest edition of its magazine, The Garden, to the surprise of readers.
The caffeine in coffee has been found to keep slugs and snails at bay. Many coffee shops offer customers grounds from their machines free of charge, and spent coffee can be used as a mulch or to improve compost. The RHS says this is within the law, but a gardener who uses coffee to kill or deter a slug could fall foul of the regulations and, in theory, face heavy fines. In practice, the RHS said there is little possibility of police arresting someone sprinkling coffee around their brassicas, but the rules are there to stop people using "home-made remedies in a dangerous manner".
EU rules state that any active ingredient or chemical must be explicitly approved for use and placed on an EU list of pesticides. As neither coffee nor caffeine has been through a UK or EU test, its impact on the environment, on gardeners themselves, and other garden creatures is not known, and its use as a slug deterrent is thus unauthorised.
Andrew Halstead, principal scientist for plant health at the RHS, which is the leading source of advice for UK gardeners, told The Independent on Sunday that it was easier for the EU to include chemicals that have been tested and approved as pesticides on a list, and impose a blanket ban on everything else, rather than produce a longer list of ingredients that are potentially dangerous.
Dr Halstead said: "All chemicals being used to control or deter animals are classed as pesticides in the UK and EU, and must be registered and approved for this purpose by our own government and the EU. Legislation requires potential pesticides to be extensively tested for effectiveness, environmental safety, operator safety and safety of breakdown products before they can be sold and used. Anything that has not been through the system is illegal to use as a pesticide, however safe that chemical is perceived to be. Heavy fines can be imposed for breaches of the laws relating to pesticide use; however, the chances of being prosecuted for scattering coffee grounds in a garden are, I suspect, remote.
"If you were to use coffee grounds around plants with the intention of providing some organic matter in the form of a mulch, rather than as a slug control/deterrent, then the regulations relating to pesticides would not apply. This may all sound rather daft, but the intention of the pesticides legislation is to prevent people from applying untested dangerous chemicals."
Bob Flowerdew, a regular on Radio 4's Gardeners' Question Time and the author of books on organic gardening, said: "Regulations are an ass, but they haven't led to prosecutions. I cannot recommend that anyone breaks the law, but I can point out that, in other countries, people do use coffee grounds."
Mr Flowerdew pointed out that gardeners used soft soap on plants to kill aphids, although this would also be technically illegal under EU rules. "As long as you say, 'I'm not killing the aphids, I'm giving them a wash, but oh dear they seem to have died accidentally', it's OK. It's the British way: we work our way around the regulations."
Can we eat slugs?
The problem of slugs is a perennial one for gardeners, and some may consider them to be neither use nor ornament. However, in a 2009 episode of River Cottage, the TV chef Hugh Fearnley-Whittingstall came up with one rather unappetising use for the pesky creatures – eating them. However, Dr Stuart Bailey, a malacologist (an expert in molluscs), said he would not recommend this.
He warned: "There is a slight risk of parasite infection from eating slugs, and there have been a few recorded cases in Japan of people contracting very nasty illnesses after eating them. The problem is that slugs like to feast on animal faeces, which is why you can get parasites from them. Even when cooked, a slight risk remains." He added that the danger of parasites could be removed if slugs were farmed in the way snails are, to control their diet.
"If you kept them in captivity for a couple of years or so and bred them for that purpose, there is no reason why you couldn't eat them. However, I still wouldn't recommend it, as they're not tasty."
Dr Bailey is a keen gardener himself, and says he uses slug pellets around his more precious plants, as well as putting some of the slugs he finds in the freezer to kill them.
He said: "Slugs do get a bad press, and they probably deserve it, although I'm speaking as a gardener rather than a scientist here."