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Slugs: 5 reasons to value them, and 5 tips to manage them

Slugs: 5 reasons to value them, and 5 tips to manage them

Small slug on a leaf

We do like a challenge.

Spring 2024 is bedding in as I write this, our delicate plants are starting to emerge from the soil. Those we have lovingly nurtured from seed in kitchens, greenhouses and sheds are now being panted out. And for many of us, we’re losing the whole lot to a rampaging army of shell-less, terrestrial, gastropod molluscs.

It’s a consistent, frustrating game. There probably couldn’t be a worse time to defend our familiar acquaintance the slug. But let’s have a go. Here are five reasons to at least give them a bit more leeway.

5 reasons to give slugs a second look

1.      Most slugs do not eat plants. 

There are thirty species indigenous to the UK and the majority of them eat decomposing material, helping to shred it down into smaller forms that microbes and other smaller soil life can break down further. That’s a very valuable process and they play an important part in it. The Leopard slug even eats other, plant-eating slugs. Kill Leopard slugs and you make your plant-munching problems worse.

2.      Slugs are an indigenous part of our wild landscape and a lot of things need them around.

Slugs have evolved alongside everything else here and they form a part of the complex web of life. A wide range of animals predate them, particularly amphibians like frogs and toads and Thrushes who love them. Ground Beetles are probably the most effective predator of slugs and a healthy population of ground beetles, in a rich Nature Garden, can have a major impact on slug numbers.

3.      Like them or not, they are definitely pretty remarkable

Image of a slug on grass

Just for looks they are quite something, with around 27,000 teeth that they lose and replace just like sharks, green blood and a body that can stretch to twenty-times its normal length. They don’t hibernate like snails do, so they’re active all-year round in temperatures over 5 degrees, smelling with their tentacles and moving around on a slime that acts as a route marker to find their way home, as well as a protective layer and lubricator. They are a marvel of evolution, if a little frustrating to us at times…

4.      They might be pollinators

Some slugs have been shown to perform a process called ‘malacophily’ – slug-based pollination. At night and in the wet, when most pollinators are in hiding, studies have found that some slugs appear to play a part in the pollination of some flowers. So far, it hasn’t been studies widely enough to know how widespread or important this process is, but who knows, maybe there is a bit of give and take going on. 

5.      Even organic pellets are a bad idea

Admirable though slugs are in many ways, it doesn’t help when they are eating through your lettuces. Synthetic chemical slug pellets are now banned but pellets labelled as permitted for organic use are still sold widely. Almost all of these contain ferric phosphate, which is insoluble and so isn't easily absorbed by animals, which is why they are considered of limited risk. They almost certainly deliver a very unpleasant death-by-poisoning to slugs, which is no good thing in itself.

But, very importantly, a substance called EDTA is often added to the pellets (and not listed on the packet) to make the ferrous phosphate more absorbable by the slugs (and so also other animals), and so more effective. EDTA has been shown to be toxic to earthworms and that is a significant area of concern, and no doubt it is a risk to other animals too. Like most easy fixes, “organic” slug pellets are not the solution.

Five tips for finding a balance

1.      Drop some of the myths

Image of a slug on a twig

Copper works sometimes, if you use a lot of it. But that costs a bit and is very fiddly at any scale.  And some studies suggest it has very little effect. An RHS study found that coffee, egg shells, wood ash and grit all have no real effect on deterring slugs. Diatomaceous earth seems to have some deterrent effect but it will wash into the soil and is likely to have a negative impact on a wider range of invertebrates than just slugs.

Raw, unbleached wool and garlic spray offer a little more hope. Both seem to have genuine deterrent effects and may help keep slugs away from precious plants for a while.

2.      Nematodes do work

A classic, contemporary organic gardening technique for managing slugs is to buy a packet of nematodes, like “Nemaslug”, that contain a collection of these tiny, worm-like soil invertebrates which predate slugs. They are genuinely effective over a smaller area but it is an expensive solution for larger areas.

3.      Celebrate nibbles

There is a difference between slugs destroying your crops and plants, and slugs taking nibbles. Nibbles are a thing to celebrate. They are signs of a garden alive, of food for Thrushes, hedgehogs and frogs and of a functioning ecosystem.

To celebrate this requires us to see things differently. It’s not about hoping for plants with displays of perfection, no sign of “damage” and perfect leaves and petals. In a Nature Garden, plants provide beauty, aroma and food to us and our wild visitors. Plants are a thing to be nibbled. Nibbles are a sign of a living, breathing Nature Garden.

Easier said than done of course. Some years are worse than others, as a result of weather, climate, predation and developments in the garden or wider area to name a few. Even a garden in balance will fluctuate. There is no need to celebrate serious damage. To avoid that, we turn to the next two tips.

4.      Apply Nature’s patterns

Here are a few approaches to apply to the Nature Garden, which align with the patterns or nature.

Image of a slug on strawberries

·       Let things reach a more mature state than you otherwise would, before planting out. More mature plants have thicker and firmer stems and more leaves, giving them a better chance of surviving slug attention. Hold them back in their pots or the greenhouse for longer, until they are more mature, before planting out.

·       Try out naturally-slug-resistant plants. When presented with alternatives, slugs will tend to avoid eating plants with thick fleshy leaves, like Sedum, plants with hairy leaves, like Geranium, plants that have toxic leaves, like Foxglove, Euphorbia and Aquilegia, plants with herb-flavoured leaves like Rosemary, Salvia, Lavender and Agastache and plants with shiny leaves like Camellia or Mahonia. The RHS has a nice list of more slug-resistant plants at 

·       Experiment with alternative varieties. Some plants are just loved by slugs. Hosta is a great example. Even then, slugs do prefer some to others. Presented with a choice, they will tend to opt for green Hostas over blue ones, so perhaps grow both, but put your hopes in the blue ones for longevity.

·       Distract with tastier options. Slugs will go towards what seems best to eat. Sacrificial plants are a key way to tempt slugs away from your precious plants. Planting out plants that slugs can’t resist, fairly near (but not next to) the plants you want to distract can help keep them away, at least while the plants are young. Chamomile, Hostas, Sunflowers, Violets, Lettuce and Cabbage are all good sacrificial plants.  You may want to grow some of these anyway, so why not grow some for sacrifice and some for you and see if you can meet in the middle. They also love citrus skins, which can be a very effective distraction. 

5.      Build a garden in balance

Image of a frog

There is no doubt that a garden with a healthy community of slug-predators is in much better shape to help hold back onslaughts. Over time, the predator-prey balance can broadly be found. (That doesn’t mean you won’t face heavier and lighter slug days. All gardens will!)

Support these predators with habitats, ideal conditions and food, and they will stick around to help out.

·       Amphibians: Frogs, Newts and Toads are all fantastic slug predators

·       Thrushes: Of all common garden birds, the Thrush is the main slug (and snail) devourer

·       Slow worms and Hedgehogs: Both a little rare and both a joy to have in the garden for their own sake, both slow worms and hedgehogs are effective slug predators. In fact, having slugs will help convince them to come back a second time.

·       Ground Beetles: They may be the smallest of all the predators here, but studies suggest they are the most effective predator for slug control.  Encouraging a healthy population of ground beetles in your garden can be the most effective way to keep control of slug numbers.

(Our unique “10 Steps to a Nature Garden” course provides more information on tips and methods for working with nature to control a wide range of more bothersome wild visitors, including more top tips for managing those pesky slugs. Have a look at the full course outline here).


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