Why snails love city gardens best

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The common garden snail, Helix Aspersa, was extinguished in the British Isles by the Ice Age. The English Channel opened up and cut us off from the Continent before it had time to make its way back again. But then came the Romans, bringing with them their own supply for culinary purposes. Unfortunately, they did not consume them all. Some escaped, naturalised and thrived. And they thrive best in close proximity to humans. For a snail four things are essential: moisture, food, shelter and alkaline soil for the calcium to make their shells. A town garden provides these necessities better than anywhere - a food supply in easy reach of the shelter of walls and paving and ideal atmospheric conditions: a small garden is so easy to water. The irony is that the people who provide this ideal environment are the very same who suffer most from the snails' presence. They even share the same taste in plants: broad-leaved herbaceous perennials.

Any city gardener visiting a country garden cannot fail to notice the relatively pristine condition of plants. There is a better range of predators, but the size and viscosity of a mature garden snail give it strong protection. Then again, in the country it is often too far for the snails to traipse from their shelter to the borders and back before daybreak. And country gardeners are less likely to have an irrigation system.

If slug pellets are not an option, whether for fear of disapprobation or concern for the environment, what can the beleaguered city gardener do? There are the recognised "friendly" methods: grapefruit halves; beer; expensive packs of aluminium sulphate; eggshells, grit or ashes; greasing the rims of plant pots. But in the end the battle, as the summer progresses, is lost, and the hosta leaves are reduced to skeletons, the crambe to Brussels lace.

The EC has been looking into the use of a suitable nematode as a means of controlling slugs in farming. But it turns out this nematode only fancies a certain type of slug and 1,000 are required to deal with one slug. The cost is therefore prohibitive.

Daily vigilance and knowledge of their habitat is probably more useful in dealing with the city snail. Then a decision can be taken on how best to despatch them. Lobbing the catch over the wall next door is totally ineffectual: snails are territorial and can travel up to 40 metres a night; by the following morning they will be back. Added to which, the mucus trail grown snails leave acts as an inhibitor to the younger generation. Kill an adult and the next size down start eating themselves silly in the race to take over the vacant patch.

Which they do. Hermaphroditic, every mature garden snail reproduces itself approximately 200 times a season. They can live for eight years once mature. Happily, snails are not vigilant parents and leave the offspring to fend for themselves. However, one gardener in Hampstead counted her haul last year - 3,000. If each of those 3,000 had lived to produce its 200 offspring, and if only five per cent of those had reached maturity, by the end of 1998 they would number six million. And if she found 3,000 how many did she miss?

How do you despatch 3,000 snails humanely? Appealing creatures, they actually become friendly in captivity. To drown them is heartbreaking - they will keep climbing back out of the barrel, eyes on stalks, bodies straining with the effort. Throwing them out on to the road to take their chance? Christian to the lions. The poor things inch their way painfully over the gritty tarmac, unable to take evasive action when the cars bear down. Squashing them underfoot is quick and not dissimilar to being hurled about by thrushes. For those with compost heaps, dropping them first into boiling water avoids the rotten fish combined with uric acid smell their decomposition produces. For those without, leaving them on the path for passing wildlife leads to infestations of bluebottles. One gardener took to burying her dead but to bury up to 40 snails a day is, so to speak, quite an undertaking.

Two possible final solutions came from the snail farmer who revealed the friendliness of their natures. His first option he called "gardeners' revenge", which is to say, eat them. But first they must be purged. Two days' starvation in a damp atmosphere in a covered bucket followed by three of feeding (flour or Weetabix) and a further two days' abstinence. Store alive in a warm box until required. Finally, blanch in boiling water and cook in garlic butter.

Should the above solution not appeal, mash up packets of Weetabix and lay trails of the cereal on damp evenings along paths and hard surfaces six inches or so from the flowerbeds. Between 11pm and 1am return with torch, dustpan and brush and sweep everything up again; slugs and snails alike will be heads down in the cereal. Place in covered pail and when convenient release on wasteland at least 40 metres from your garden. Repeat regularly throughout the season.