Snails

Snails are gastropods; single-shelled, soft-bodied animals in the molluscs group of animals. Snails, along with slugs, use their rasping tongues to eat holes in leaves, stems and flowers of many plants. There are many control options available for slugs and snails but despite this they remain a persistent pest. The RHS is carrying out a scheme of research on gastropod control methods to improve the advice we can give to home gardeners.

The snail most commonly encountered in gardens is the common garden snail, Cornu aspersum. Banded snails, Cepaea species, which are a little smaller and often brightly banded yellow, white and brown, may also be numerous, but these are much less damaging to plants.

Snails are most active after dark or in wet weather, and the tell-tale slime trails, if present, can alert you to the level of activity.

Snails eat a wide range of vegetables and ornamental plants, especially seedlings and other soft growth. They are good climbers and can be found high up in some plants. Most damage is done in spring by snails feeding on seedlings, new shoots and plant crowns. Snails will also eat decomposing organic matter such as rotting leaves, dung and even dead slugs and snails.

You may see the following symptoms:

• Snails sometimes leave behind slime trails, which can be seen as a silvery deposit on leaves, stems, soil and hard surfaces
• Snails make irregular holes in plant tissues with their rasping mouthparts. Young shoots and leaves are damaged or eaten, not only at ground level but often high up

Snails are often so abundant in gardens that some damage has to be tolerated. They cannot be eradicated so target control measures on protecting the more vulnerable plants, such as hostas, seedlings, vegetables and soft young shoots on herbaceous plants.

Non-chemical control

There are various measures you can take: 

• Transplant sturdy plantlets grown on in pots, rather than young vulnerable seedlings. Transplants can be given some additional protection with cloches
• Encourage predators such as thrushes, toads, hedgehogs and ground beetles. The biological control nematode (‘Nemaslug’), Phasmarhabditis hermaphrodita, is used to control slugs in the soil but is unlikely to control snails, since they spend most of their time at or above soil level
• Place traps, such as scooped-out half orange, grapefruit or melon skins, laid cut side down near vulnerable plants, or jars part-filled with beer and sunk into the soil. Check these and empty them regularly, preferably every morning. Proprietary traps and barriers are also available from garden centres and mail order suppliers
• Place barriers, such as copper tapes around pots or stand containers on matting impregnated with copper salts. Moisture-absorbent minerals can be placed around plants to create slug barriers .Gel repellents can also be used to create barriers around plants. These products are widely available from garden centres and mail order suppliers
• Go out with a torch on mild evenings, especially when the weather is damp, and hand-pick snails into a container. Then, either take them to a field, hedgerow or patch of waste ground well away from gardens, or destroy them in hot water or a strong salt solution
• Turn over likely hiding places in winter to expose snails for thrushes to feed on

Chemical control

Following the manufactures instructions scatter slug pellets thinly around vulnerable plants, such as seedlings, vegetables and young shoots on herbaceous plants. It is important store pellets safely and scatter them thinly as they can harm other wildlife, pets and young children if eaten in quantity.

There are two types of pellet available to the gardener; those that contain metaldehyde (e.g. Bayer Ultimate Slug and Snail Killer, Deadfast Slug Killer, Doff Slug Killer Blue Mini Pellets, Westland Eraza Slug and Snail Killer) or ferric phosphate (e.g. Growing Success Advanced Slug Killer, Bayer Garden Slug Killer, Bayer Organic Slug Bait, Vitax Slug Rid, Doff Super Slug Killer, Sluggo Slug & Snail Killer, SlugClear Ultra3). Ferric phosphate is approved for use by organic growers and is relatively non-toxic to vertebrate animals.

Most plants, once established, will tolerate some snail damage and control measures can be discontinued.

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Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)

Snails and slugs cause similar damage and can climb, often to a considerable height, above ground level. Because of the protection provided by their shells, snails can move more freely over dry terrain than slugs.

Snails are less common than slugs where acid soils prevail and, unlike slugs, they remain dormant over winter, often clustering together under empty upturned flower pots, stones or other protected places.

Reproduction occurs mainly in autumn and spring, when clusters of spherical, yellowish-white eggs can be found under logs, stones and pots.

Some herbaceous plants are less likely to be eaten by slugs and snails, these are listed below

Acanthus mollis (bear's breeches)
Achillea filipendulina
Agapanthus hybrids and cultivars
Alchemilla mollis (lady's mantle)
Anemone × hybrida (Japanese anemone), A. hupehensis (Japanese anemone)
Antirrhinum majus (snapdragon)
Aquilegia species
Armeria species
Aster amellus, A.× frikartii, A. novae-angliae (Michaelmas daisies)
Astilbe × arendsii
Astrantia major
Bergenia (elephant's ears)
Centaurea dealbata, C. montana
Corydalis lutea
Cynara cardunculus (globe artichoke)
Dicentra spectabilis (bleeding heart)
Digitalis purpurea (foxglove)
Eryngium species
Euphorbia species (spurges)
Foeniculum vulgare (fennel)
Fuchsia cultivars
Gaillardia aristata
Geranium species
Geum chiloense
Hemerocallis cultivars (day lilies)
Papaver nudicaule (Iceland poppy)
Pelargonium
Phlox paniculata
Physostegia virginiana (obedient plant)
Polemonium foliosissimum
Polygonum species
Potentilla hybrids and cultivars
Pulmonaria species (lungwort)
Rudbeckia fulgida
Salvia × superba
Saxifraga × urbium (London pride)
Scabiosa caucasica (scabious)
Sedum spectabile (ice plant)
Sempervivum species (houseleeks)
Sisyrinchium species
Solidago species (golden rod)
Stachys macrantha
Tanacetum coccineum (pyrethrum)
Thalictrum aquilegiifolium
Tradescantia virginiana
Tropaeolum species (nasturtium)
Verbascum species (mullein)  

Birds: encouraging into the garden
Encourage wildlife to your garden
Leaf damage on woody plants
RHS research on slug and snail control
Slugs
Vine weevil