Snail shells and how they get their colours and patterns

I do know that snails are the bane of most horticulturists’ lives who will go to many lengths to deter or prevent these stubborn gastropods from ruining their much toiled over gardens. But you see, I am to gardening what Rab C Nesbit is to personal hygiene (willingly neglectful) and therefore I do not see snails as the enemy but instead am rather fascinated by them.

There are upwards of 120 different varieties of snail in this country, and the average British garden is home to several thousand at any given time. You probably know that they are hermaphrodites (ie have both male and female reproductive organs), but they need to mate and exchange sperm to have babies, which they do around February and March. They lay their fertilised eggs in dark moist places, often underground, and it takes around 15 to 21 days for them to hatch, depending on the species.

Initially, the baby snailettes, which are born with a wafer-thin flimsy shell, eat the calcium-rich eggshell from which they hatched to see them through the first five days or so. But after that, they have to go in search of more fodder to continue to thrive. As they emerge into the open air they are extremely vulnerable to an array of hungry predators which is the reason their average lifespan is a mere nine to 12 months, even though they can live longer. Their first and urgent mission is to find sources of calcium to grow and nourish their hardening protective shell.

Their distinctive shells are formed thanks to an organ called the ‘mantle’ which secretes layer upon layer of calcium carbonate to build size and thickness. Green vegetables such as broccoli, spinach, cabbage, and lettuce are particular delicacies, as are flowers like hosta, marigold and rudbeckia. The swirly shape is thanks to the way in which the calcium carbonate is secreted, and in almost every case flows in a right-handed, or clockwise, direction, otherwise known as dextral. There is the odd species that has a left-hand swirl which is referred to as ‘sinistral’, but they are pretty rare.

You can use pesticides to control the snail population in your garden, but there is a trend to more environmentally friendly methods. There are a surprising number of snail-repellent flowers, vegetables and herbs (a quick Google search will tell you what they are) and you can take steps to make your patch an attractive des res for natural predators like birds and hedgehogs. Again, Google is your friend if you want tips on how to draw them in.

Incidentally, if you spot a rock that is surrounded by cracked snail shells, this is likely to be a bird’s anvil stone. Garden birds like the song thrush love eating snails, and cleverly use the rock to bash it and crack open the shell. If a snail is ever separated from its shell, it cannot survive.

Snails love to hide in the daytime in warm, moist places, so another suggestion is to lay planks within your flower borders before nightfall, and then first thing the next day, lift them up and collect any snails you find hiding underneath. They will graze an area of no more than about 20 metes around the spot where they were born and get very disorientated if they are moved further away so if you take them out into the countryside and set them free in a woodland, for example, they won’t be able to find their way back.

Of course, with thousands at a time dwelling in your garden, you might need to make a lot of trips. But perhaps, if you embrace all of these deterrent methods, alongside a healthy dose of persistence, you might just end up with a full crop of lettuce this year.

• Do you have memories to share or ideas for this column? Contact me via my webpage at countrymansdaughter.com, or email dst@nne.co.uk.