Slugs have a PR crisis in the gardening world. But do they really deserve the bad rep? RHS entomologist Hayley Jones sheds light on the little-known benefits slugs bring to ecosystems
It’s probably safe to say that most gardeners, wearied by the memories of munched courgettes or vanished seedlings, don’t view slugs with the same fondness as some other garden wildlife.
However, slugs play valuable roles in our gardens and ecosystems, and the number of slugs that are ‘pest species’ on our garden plants is actually low in proportion to the wide array of fascinating slugs found in the UK. RHS entomologist Dr Hayley Jones is here to introduce us to who’s who and what they do.
How can I tell which slugs I have in my garden?
Slugs are actually really hard to identify without close-up examination from all angles alongside a reliable ID guide. Sometimes, two species can only be distinguished through dissection.
However, you can get an indication of which family a slug belongs to from the position of the breathing pore, whether or not it has a mucus pore, and the pattern of wrinkles on the mantle (section between head and tail). Watch our videos further down the page to get started with some helpful slug ID tips.
The plant munchers
These are slugs that do really like the taste of your prized hostas, young lettuces and other leafy treats around your garden. However, it’s important to remember that there is no effective or sustainable way to get rid of slugs and the best approach is to encourage a healthy and balanced ecosystem in your garden that promotes natural predators, tolerate some level of damage, and reduce risk to vulnerable plants where possible, such as by raising
A seedling is a young plant grown from seed.
seedlings indoors and then planting out when they are larger.
Mantle (smooth, saddle-shaped area between head and tail) usually has a pale centre
Deroceras invadens
Arion ater
Large black slug
Key features:
Medium to very large slug
Variable colour from yellow to black
Contracts into a hump and squirms from side to side when disturbed
The good guys
Gardeners may have traditionally viewed slugs as the enemy, but we are now beginning to understand just how important they are in the garden ecosystem.
Most slugs are great garden recyclers, grazing on algae, fungi and detritus. Many species feed on decomposing organic matter, such as dead leaves, dung, and even dead animals. They are beneficial animals to have in a garden as they are a valuable part of the
Composting is the process by which plant material is heaped together to rot (decompose) to produce compost. Garden or kitchen waste can be broken down over time in a compost bin or heap to produce crumbly organic matter that can be used as a mulch, soil conditioner and a constituent of potting compost.
composting process – you may have seen them feasting in your
Can refer to either home-made garden compost or seed/potting compost: • Garden compost is a soil improver made from decomposed plant waste, usually in a compost bin or heap. It is added to soil to improve its fertility, structure and water-holding capacity. Seed or potting composts are used for growing seedlings or plants in containers - a wide range of commercially produced peat-free composts are available, made from a mix of various ingredients, such as loam, composted bark, coir and sand, although you can mix your own.
compost bin, helping to turn plant waste into compost for gardeners to use.
The leopard slug, which in itself doesn’t pose a threat to your plants, is highly territorial and actually scares off other slugs – a guard slug! So, slugs can in fact be a gardener’s friend.
Green cellar slug
Key features:
Medium to large slug
Mottled with greenish blotches
Plump body and tail
Limacus maculatus
Testacella scutulum
Orange or golden shelled slug
Key features:
Golden-yellow speckled body with bright golden yellow underside
Small flattened shell near the tail
Slow-moving and dry to the touch
Slugs are one of the many things that stops everything lying around dead all the time
Even if you are struggling to warm to the slugs themselves, remember that they are important food for other garden wildlife, such as birds, frogs, toads, hedgehogs, slow-worms and ground beetles.
The cool ones
Slugs are far from boring, and some bring really interesting features to the table. The ash black slug, a woodland specialist, can grow up to 30cm long and can be an indicator of ancient woodland. The
A native plant is one that originated or arrived naturally in a particular place without human involvement. In the British Isles, native plants are those that were here during the last ice age or have arrived unaided since.
native shelled slug does indeed have a shell (yet is not a snail), lives almost entirely underground, and is carnivorous, feeding on worms.
The tree slug feeds on algae and lichen at the tops of trees – it can be seen gliding up the tree in the evening looking well hydrated, and coming back down again in the morning looking distinctively shrivelled after a hard night’s cleaning.
Some slugs offer a free greenhouse cleaning service, leaving distinctive patterns as they move over the glass grazing on algae
You will never be able to get rid of slugs. The UK has the ideal conditions for slugs. But then again, why would you want to?
Maybe, next time you spot a slug in your garden, you’ll see it differently. Curious to find out who’s visiting? Check out our handy videos below to brush up on your slug ID skills, grab a torch and get slug spotting!
Getting started with slug identification
Identifying slugs to family level
About the author – Olivia Drake
With a background in biology, Olivia is passionate about sustainable horticulture and the role gardening can play in conservation. She is professionally trained as a botanical horticulturist and has worked in public gardens around the UK and abroad.
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.
