Slugs: The good, the bad, and the stomach-churningly disgusting

Many years ago, I was sitting next to a handsome, ambitious sort at a Boxing Day lunch. He turned to me with a charming smile and asked what my best Christmas present had been. A collection of large-scale OS maps, I said, beaming. His face fell; we didn’t hit it off. Goodness knows what he would have made of my best present this past year, a book called Slugs: Friend or Foe? by Hayley Jones.

I have often been plagued by guilt about these most monstrous of garden pests. Dr Jones advocates a zen-like, therapeutic approach: we have nothing to fear but fear itself, she insists. She encourages us to get to know, understand and sympathise with what is possibly the greatest garden demon.

Demons are disgusting looking and, there is no denying it, so are slugs. They developed from their less reviled relatives, snails, of the phylum Mollusca and the family gastropod, those who walk on their stomachs and operate at night to keep ‘moist’. Slugs, having shed their shells to squeeze themselves into damper reaches, took on something of the dark.

Their slime has phenomenal lubricant qualities, deterring predators with its foul taste and gumming up their mouth parts. Slugs are made up of strangely named elements; tubercles, mantles, saddles, breathing pore and tail. Not only do they walk on their stomachs, but their anus is by the mouth, where lies the ravenous radula, or tongue.

Dr Jones’s most convincing argument in favour of the slug is that only seven of the 45 species found in farms and gardens do any damage at all and 17 are our friends. Indeed, half the species we see are cleaner-uppers, scientifically known as ‘detritovores’ — they recycle dead matter, even consuming carrion waste and faeces by means of that cheese-grater radula. Many live on fungus. There are others whose diet still remains a mystery. On the upside, slugs are the favourite meal of birds, insects and mammals, holding a vital place in the garden ecosystem.

In an effort to cultivate affection, I dreamt up a bougie paint-colour chart based on their attributes: Breathing-pore Pink; Foot-fringe Orange; Dusky Subfusc; Pale Sole; Mucus Yellow. It’s not enough, however, to counter the rage on finding the tender dahlia shoots have been shredded.

To every slug there is a season and spring and autumn are their moments. Once it gets hot, gardens are safer. Now is the time to set up our barricades; beer traps and coffee grounds, copper tape and garlic in solution — all help to make you feel good. Like me, Dr Jones is unsure of the efficacy of any of the multifarious disruptors regularly suggested in gardening columns. She is certain of one thing, however: ‘always water in the morning’, because they are night creatures.

It also helps to direct sow as late as you can: the key egg-laying periods are March–April and September–October, which is when we need to employ all the humane methods available to lure the neonates away from our treasures. Grow sacrificial plants; encourage predators; let chickens in the garden; border the garden with wilder patches, a pond, untidy hedges and long grass. Wet places bring in the mega predators — toads, frogs and hedgehogs. Brown rats, badgers, shrews and moles do a good job, too. Humans are good at collecting slugs in buckets. Best of all are slow worms. Who guessed they hoovered up slugs with relish?

Probably the most abiding predators, however, are members of the beetle family, including those elusive, almost vanished, popstars of the night, glow-worms. Their larvae feed on slugs and snails, injecting a paralysing digestive juice through their bite. Ground beetles, especially the violet ground beetle, can put a stop to any slug’s revolting mucus production with a rapid nip to the back of the head.

Equally helpful are millipedes and earwigs, so it is important to keep all these garden workers happy. Birds, too, owls, fieldfares, rooks and blackbirds — we have a fine feathered militia here, which is crucial. It is all about food chains.

Devastation of a newly planted row of cabbage seedlings is hard to take, however, and, if you can be faffed with nematodes (at considerable cost), that is the way to go for serious growers. A few ‘irregular holes’ in your hostas? I would pour garlic-flavoured cream on your enemies.

Isabel Bannerman is, with her husband Julian, a leading garden designer — see their website to find out more about their projects.

This feature originally appeared in the issue of Country Life. Click here for more information on how to subscribe.