Know Your Slug Before You Fight It

Most of the damage in a British garden is done overnight, and it is rarely the big grey field slug you spot sliding across the path at dusk. The worst offenders are small keeled slugs, often less than 3cm long, that live in the soil and emerge after dark to rasp neat holes in the softest leaves they can find. Seedlings of lettuce, delphinium, hosta, bean and brassica are prime targets because their tissue is thin and tender.

Slugs are also creatures of habit. They follow the same slime trails night after night, sheltering under clods, mulch, stones and low-growing weeds during the day. Understanding that routine is the key to control. Rather than declaring war on the whole population, you can simply make the journey from shelter to seedling as difficult, dry and dangerous as possible. Damp, mild evenings after rain are peak feeding time, so expect to be busiest in spring and again in early autumn.

Physical Barriers That Earn Their Keep

A barrier only works if it stays dry and intact, so place it before the slugs arrive rather than after the first nibbled leaf appears. Copper tape and copper rings give a slight electric tingle to slugs crossing them, and they work well around raised beds, pots and individual plants. Clean the copper occasionally with a vinegar-water wipe, because oxidised metal loses its punch.

• Crushed eggshell, sharp grit and horticultural wool: cheap, effective and harmless to birds. Refresh after heavy rain.
• Wood ash or lime: a thin ring around brassicas helps, but avoid it where you have acid-loving plants nearby.
• Barrier collars: a plastic bottle with the base cut off, sunk 2cm into the soil around a transplant, protects the stem completely.
• Copper mesh tape: fix around the top edge of raised beds and pots to stop slugs climbing in from outside.

Remember that barriers protect what is inside them, not what is already there. Check the soil at planting time and remove any lurking slugs before you set the barrier in place.

Night Checks: The Most Reliable Method

Nothing beats a torch and ten minutes after dark. Go out around an hour after sunset with a head torch and a bucket of soapy water, and pick slugs off by hand. This sounds tedious, but a fortnight of regular patrols in late spring can cut the population dramatically and it costs nothing.

Look under the obvious places: the rims of pots, plant labels, the underside of leaves, the joins of brick edging, damp mulch and the base of walls. Drop what you find into the bucket, or relocate them a good distance away in a hedgerow if you prefer not to kill them. Morning checks matter too — slugs retreat as light strengthens, so a quick pass at 7am catches the stragglers before they disappear into the soil.

Encourage the Wildlife That Does the Work for You

Slugs have plenty of natural enemies, and most of them are the birds you already want in your garden. Thrushes, blackbirds, robins, wrens and song thrushes will happily take slugs and their eggs, particularly in early spring when other food is scarce. A garden that is tidy to the point of sterility offers them nothing.

• Leave a wild corner: a log pile, leaf litter or a patch of long grass gives beetles and centipedes somewhere to hunt.
• Put a bird bath or shallow dish among the beds — birds work closer to cover when water is nearby.
• Encourage hedgehogs with a gap in the fence and a quiet, sheltered spot. Never use metaldehyde pellets, which can be lethal to them.
• Welcome frogs and toads: a small pond or even a damp, shaded refuge will bring them in, and they are voracious slug eaters.

If you must use pellets, choose ferric phosphate-based ones, which break down into iron and phosphate in the soil and are far kinder to wildlife. Use them sparingly and never scatter them where birds, pets or hedgehogs feed.

Clever Planting to Reduce Losses

Some of the best protection is simply planning around the problem. Raise the toughest plants first and give tender seedlings a head start indoors, then transplant them out only when they are sturdy enough to shrug off a nibble or two. A strong lettuce planted out at 8cm tall will survive damage that would finish off a direct-sown seedling.

Thin your sowings ruthlessly and early. Crowded seedlings are weak, damp and irresistible. Water in the morning rather than the evening, so the soil surface dries before the night shift emerges, and water the roots rather than the foliage where you can. Drip lines and soaker hoses are excellent for this.

Try a sacrificial row of something slugs adore — a few spare lettuce or marigolds planted well away from your precious crops. It concentrates the damage in one place and gives you a nightly gathering spot. And keep the hoe moving: removing weeds, especially chickweed and groundsel, takes away the daytime shelter that slugs rely on between meals.

Traps, Lures and the Long Game

Traps work best as a supplement, not a solution. A sunken jar of beer, a hollowed-out half orange or a upturned grapefruit skin placed cut-side down will collect slugs overnight — empty them each morning into the compost or the bin, not onto the soil. Damp rolled-up newspaper or a cabbage leaf laid on the ground makes an excellent daytime trap, since slugs will gather under it and can be removed in one go.

For persistent problems in a small area, biological control in the form of nematodes watered onto moist soil in spring is very effective against soil-dwelling slugs and completely safe for birds, pets and children. It works best when the soil is warm and damp, so apply it after rain in late April or May rather than in a dry spell. Combine it with barriers and night patrols and you will find that by midsummer your seedlings are surviving with very little intervention at all.