Slugs are the bane of gardeners’ lives, regularly topping surveys of garden pests. They munch the new growth of precious plants, demolish seedlings overnight and munch irregularly-shaped holes in leaves, stems, flowers, tubers and bulbs and potatoes, leaving their silvery slime trails behind.
Slugs are active for most of the year but are a particular problem in spring, when there’s plenty of young growth for them to eat. They are mostly active after dark, especially when it’s warm and damp. In hot, dry weather they bury themselves in the soil or hide in cool, dark places to avoid dehydrating.
There are over 40 species of slugs in the UK. Not all slugs eat live plants, however – many of the larger ones eat decaying or dead plant material and they are an important part of the composting process.
Despite your best efforts, some losses to slugs are inevitable. Accept that your garden is never going to be slug free, and find ways to work around this.
Make sure you prioritise the protection of the most vulnerable plants – all seedlings, new growth on most herbaceous plants, and all parts of especially susceptible plants such as delphiniums, hostas and dahlias. If you’re growing plants in pots, make sure there isn’t a ‘bridge’ of leaves from one plant to another, as slugs can travel from pot to pot this way.
Sow extra seeds so you have seedlings waiting in the wings to replace any that are eaten by slugs, and grow more than you need so you still have some crops left over after a slug attack. And add plenty of slug-resistant plants (see our list below) to keep damage to a minimum.
There are many options for controlling slugs. The best approach is to combine several methods, starting early in spring. Here are some ways to controlling slugs in your garden, some of them recommended in a survey of readers of BBC Gardeners’ World Magazine.
How to control slugs
Create a healthy ecosystem
Ultimately, the best thing you can do to control slugs in your garden is to create a healthy ecosystem. Create lots of habitats for slug predators – hedges, shrubs (especially those with berries) and trees will all attract birds such as blackbirds and thrushes, which eat slugs (and snails). If you have room, a wildlife pond is a great addition to your garden – the newts, frogs and toads that use it will also devour slugs. Laying a slat down will attract slow worms, which eat a lot of slugs. Encourage wildlife in to your garden by creating a small hole in a fence so frogs, toads, slow worms and other species, such as hedgehogs, can travel freely between your plot and neighbouring ones. Create a log or leaf pile, or a large open compost heap, where they can make a home.
Healthy soil produces healthy plants that are much more able to withstand slug damage – slugs tend to attack plants that are already weakened in some way. So mulch your garden with homemade compost, composted green waste or well-rotted manure to support healthy soil.
Create a slug-free zone
It’s impossible to eliminate slugs from your whole garden, but you could create a small zone that you aim to keep slug free. Young seedlings and plants are by far the most vulnerable to slug attack, so prioritise the area where they grow, such as the area in and around a cold frame or a raised bed. Place fabric or mesh at the base of your pots before filling them with compost, so that slugs can’t gain entry from underneath them. Delay planting out seedlings until they have reached a decent size – they are more likely to withstand slug damage. Don’t overfeed young plants in spring, as this can create lush, leafy growth that slugs love.
Then deploy a number of the methods outlined below to keep the area free of slugs.
Create a slug zone
In a BBC Gardeners’ World Magazine survey, the most popular approach to dealing with slugs was to go out with a torch after dark to pick them off plants, bucket of salt water at the ready. The best time to do this is two hours after dusk, so this means late nights in the height of summer.
To make the job easier, you can deliberately attract slugs to a dark, shady corner using something they’re attracted to – old veg leaves, dried cat food, bread rolls, oats or bran. As they congregate for a feed at night, swoop in and collect them.
Alternatively, check slugs’ hiding places during the day. They hide anywhere that’s cool, dark and moist – under plant pots, pot saucers, tread boards on the veg plot and garden furniture. Some BBC Gardeners’ World Magazine readers also found that the old trick of using grapefruit skins or bricks can also be effective – slugs hide under them during the day. Check under these places regularly and remove any slugs you find. Slugs can also lurk under dead plant material in borders. Clear it away and it to the compost heap – the slugs will continue the composting process there.
Also look out for clusters of slug eggs in spring and autumn – slugs can lay them in batches of 50 at a time. They look like translucent white balls, a few millimetres across. They’re often found under plant pots, stones, in moist pockets of soil and in other cool, dark, places. Leave them out for the birds, or squash them as soon as you spot them. In spring, rake over the surface of the soil to expose them, leaving them for centipedes and birds.
Sprinkling salt does kill slugs, but it is also harmful to plants.
Use organic slug pellets
Slug pellets that contain metaldehyde kill slugs, but they also kill the animals that eat them, such as birds and hedgehogs. They have now been banned as a result. Sales of metaldehyde slug pellets ended in March 2021 and stocks must be disposed of by 31 March 2022. Pellets made from ferric phosphate are just as effective but are apparently less harmful to wildlife and are approved for use by organic growers. Scatter the pellets on the soil as soon as you can before tender young growth appears. Bear in mind, however, that if you scatter them liberally, you will ultimately get fewer predators coming to eat the slugs in your garden – leaving you reliant on pellets. Therefore use the pellets sparingly, around particularly susceptible plants, for example.
Water in a biological control
Many organic gardeners are turning to biological controls that contain microscopic nematodes. These infect slugs with bacteria and then kill them. Water onto the soil in the evenings when the soil is warm (it needs to be at least 5°C) and moist, from spring onwards. It is effective for around six weeks, so several applications are needed throughout the growing season. It is impractical to treat your whole garden this way, so prioritise key areas such as the veg patch or a raised bed.
Water in the morning
This ensures that the soil has dried out by the evening, when slugs are most active. Wet soil at night can create a slug highway between plants.
Copper rings can be effective slug deterrents – if a slug tries to cross one it receives an ‘electric shock’, forcing it back. Put rings around vulnerable plants such as hostas – bury them deep as slugs may reach the plant from underneath.
Some gardeners also swear by sticking copper tape around the rim of pots, although a recent trial by the RHS found this to be ineffective. Research is ongoing, however.
Let them eat bran
Slugs love bran and will gorge on it. They then become bloated and dehydrated, and can’t retreat to their hiding places, making them easy pickings for birds.
Repel slugs with a sharp mulch, a slimy barrier or garlic drench
Many BBC Gardeners’ World Magazine survey respondents swore by barriers in the war against slugs – slugs find sharp or prickly materials uncomfortable to travel over. Popular barriers included ash, bark, cat litter, cocoa chips, sawdust, sand and horticultural grit. You could also try wool pellets or coffee grounds. Bear in mind that these need topping up regularly and that most slugs live within the soil, not on the surface. A recent RHS trial found several of these methods ineffective, but their research is ongoing.
Some BBC Gardeners’ World Magazine readers also recommended a slimy, greasy barrier such as petroleum jelly or WD40 – smear it liberally around the rims of pots or seed trays. Another recommendation was double-sided sticky tape attached to the rim of pots, the outer side liberally doused in salt.
Slugs are also said to be repelled by the smell of garlic. Apply a garlic drench to precious plants in the evening, coating the leaves thoroughly. Apply regularly, especially after rain.
Try beer traps
Beer traps were also popular with BBC Gardeners’ World Magazine readers. Make a slug trap using cheap beer – slugs will be attracted to the smell. Sink a beer trap or container into the ground, with the rim just above soil level. Half fill with beer and the cover with a loose lid to stop other creatures falling in. Check and empty regularly. It’s best to place the trap on the edge of a border or veg patch – if you place it within it, the slugs will munch on your plants on their way to the trap. Another reader suggestion was to leave a few dead slugs in the bottom, to entice more in.
Grow slug-resistant plants
Consider replacing plants that are repeatedly decimated by slugs with options that are more resistant. Many plants have leathery, glossy, hairy or scented leaves that slugs tend to leave alone. Read our feature on 20 slug-resistant plants.
Here are the top 20 plants that BBC Gardeners’ World Magazine readers found to be slug resistant:
- Hardy geranium
- Alchemilla mollis
- Japanese anemone
- Ornamental grasses
- Ornamental grasses
- Lilium henryi
In the first instalment of this two-part video from the notoriously wet spring and summer of 2012, Carol Klein looks at some of the plants most loved by slugs and snails, such as hosta and Kirengeshoma palmata. She also recommends some plants to grow that they’re less fond of eating:
In the second part of her video, Carol Klein recommends more plants that are resistant to slugs and snails: