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Are slugs eating their way through your prize hostas and devastating your dahlias? Try not to worry. There are ways you can live with slugs and create a more slug-resilient garden.
So says lifelong gardener and ecologist, Jo Kirby, who has written The Good Slug Guide, a companion for the modern gardener which aims to help you change the way you think about slugs and snails, and build biodiversity to control the damage they inflict on your plants.
“It’s about keeping damage down to an acceptable level,” he explains, saying it’s important to find out about their natural enemies and work to “achieve some kind of balance where slugs and snails are reduced in numbers and don’t ever become a serious problem”.
He offers the following tips to help gardeners build a more slug-resilient outdoor space.
1. Don’t keep the garden too tidy
“Every gardener needs to know there isn’t a single slug that is fully herbivorous or vegetarian. All slugs eat other things. If you can provide those other things in the garden, suddenly the slugs have something else to feed on and they don’t have to eat your plants.
“A lot of slugs are dedicated to eating detritus. A leaf that’s being decomposed can often be as good a source of protein to a slug or snail as green leaves, and they tend to be easier to eat as well because they have fewer noxious chemicals in them.
“I would leave fallen leaves where they fall, unless you really need to move them, like on a lawn. In herbaceous borders the autumn tidy-up is a disaster as far as natural enemies are concerned, and also strips away food, so the slug has no other option than to eat your plants.”
King Charles III, he points out, has a national hosta collection. “He gets very little slug damage, but he keeps his [collection] away from the house in a woodland area where there is lots of detritus on the woodland floor.”
Won’t leaving garden detritus around just provide shelter for slugs?
“It does, but it also provides nooks and crannies for all the natural enemies of slugs and snails, and my research indicates there are around 75 of them which can be found in the garden.”
2. Be aware of plants which slugs love
We all know slugs love hostas, dahlias, cosmos and legumes, and Kirby confesses there are some that he can’t grow because the slugs will destroy them.
“I love Gypsophila paniculata (baby’s breath), which goes so well in a border especially if you’ve got dry stone walls. It’s a herbaceous perennial which grows to about 3ft and produces lots of small flowers – but I can’t grow it because it’s too popular with slugs and snails.
“Summer bedding is notoriously susceptible to slug damage, so it’s a case of really using slug-resistant plants such as fuchsias, plectranthus, which is a nice foliage plant with open heads of purple flowers in summer that’s completely slug-resistant, and pelargoniums, especially the ones with scented leaves.”
However, he warns against replacing them all with plants which aren’t attractive to slugs, saying if you do that you’ll end up with a “very strange-looking garden”.
3. Encourage natural enemies
Kirby has researched the three common predators to slugs – hedgehogs, frogs and toads.
“Unfortunately, hedgehogs and toads in particular eat an awful lot of ground beetles, and ground beetles are probably the main predator of slugs and snails in the garden. So by encouraging toads and hedgehogs, you might well be giving yourself more of a slug problem,” he warns.
“But if you include lots of detritus in your garden, you increase the diversity in that litter layer hugely by thousands of species. Then, the desirable larger animals in the garden don’t eat so many beetles.”
Centipedes, shrews, voles and mice all eat a lot of slugs and snails, he observes. A wood mouse study found that they eat more snails than thrushes, he adds.
“It’s a case of cultivating your wildlife as much as your flowers and veg. Many natural enemies are called generalist feeders. They don’t just feed off snails. Having a litter layer is important because it gives natural enemies something to feed on when there aren’t so many slugs around.”
4. Limit digging
Try not to disturb the ground too much because you may kill beneficial creatures, Kirby advises. “There’s always going to be some digging and hoeing. It’s just a case of reining it back a bit.”
5. Keep an eye on veg
The blue-black soil slug (Arion hortensis) can be a nuisance to gardeners in autumn as it will attack crops of carrots and beetroot.
“You can keep an eye on numbers by putting a board or a small sheet of plywood on the soil surface and pressing it down a bit. Then, if you look under it in the morning you’ll get and idea of what slugs you have and how many. It also helps if you do use collection as a way of limiting your slug numbers.”
6. Increase ground cover
“Most natural enemies, especially beetles, hate open ground because they are very prone to dehydration and are prone to being predated (preyed upon) if they are visible, so just fill those gaps with plants.”
