With the onset of winter and wet weather comes the unrelenting nighttime raids by hordes of snails and slugs, their one goal, to feast on all the sweetest baby leaves of any newly planted seedling. This got me wondering what, of the many organic deterrents, actually work? With this in mind I set out to try the most popular, often suggested methods for saving seedlings from these persistent feeders.
First of all, know thine enemy
The European Brown Garden Snail has been widely introduced worldwide, living mainly in cities where they enjoy the microclimates created by the home gardener who inadvertently supplies plenty of water and a fairly constant supply of tasty plants. Snails are hermaphrodites, possessing both male and female organs, and both snails will become fertilised during mating. A snail will lay around 80 eggs with up to 6 batches of eggs per year, that’s about 480 baby snails a year from just one parent!!! Snails are almost blind and deaf but have an amazing sense of smell. They have a strong muscular foot that is lubricated with mucus enabling it to traverse sharp rough surfaces, the mucus quickly sets to a glue like consistency to prevent the snail from slipping backwards and enabling it to climb smooth vertical surfaces.
Let the experiment begin
I chose five methods, all based on a theory of barriers, what the snails can’t reach they can’t eat, and one set of seedlings with no protection at all to provide a comparison. I set up my six pots, and tentatively waited, I ventured out after dark with my torch, excited to see the results, fully expecting that the undefended seedlings would be devoured within the week. A week went by and not a single nibble, I wonder whether the strong smell of both the coffee grinds and garlic were masking the smell of fresh young seedlings and the snails just weren’t aware of their existence. Winter started off fairly dry so this may also have accounted for the snails inactivity, the weather eventually turned and we had a week of soaking rain and one by one the seedlings fell, the only untouched seedlings at the end of the month-long experiment were those in the pot protected by the copper tape.
I’ve read that British scientists, lead by doctor Gordon Port, have produced a special garlic extract that proved to be effective in laboratory testing. Dr Port tested a highly refined extract of garlic oil, he believes oils in the herb damage the nervous systems of both snails and slugs but cannot say why it is so lethal. The research is unclear as to whether home-made garlic sprays used in a normal garden environment have the same effect.
To make the garlic spray I crushed and chopped three cloves of garlic and covered with vegetable oil, about one or two tablespoon, then left to steep overnight. The next day I added half a litre of water then strained it through a cloth and poured into a spray bottle with a few drops of pure soap. The mixture stored quite well in the fridge for a few weeks. I sprayed the soil surrounding the seedlings liberally with the garlic spray.
After heavy rain left me wondering whether the garlic spray was effective but getting washed away or whether my snails were not really adverse to garlic, I lay a circle of thinly sliced garlic around the seedlings. That night I crept outside with my torch to see that not only had the snails crossed the freshly sliced garlic but it looked like some slugs were actually eating the garlic. I’m not sure whether or not this killed any of the slugs or snails but the damage to my plants was done.
Did it work?
Nope. I was unable to determine whether or not the garlic had any ill effects on the snails or slugs but as a deterrent is wasn’t effective. Perhaps in dry conditions it could have some small effect, maybe disguising the smell of young seedlings which attract the snails and slugs but in wet conditions it has little to no effect.
Crushed eggshells are supposed to create a jagged, barbed wire like circle of defence.
I collected eggshells, washed them under running water, pulled out the air sack in the membrane and stored them in the freezer. When I collected enough shells I dried them on a baking tray in the oven, a few minutes in a moderate oven should do, or if you happen to be baking, then pop them into the hot oven after you’ve turned it off and leave them in there until the oven cools. I roughly crushed the shells to produce a variety of sizes and sprinkled liberally around my seedlings. I applied a second, fresh, layer of eggshells two weeks later.
Did it work?
It may have initially worked as a deterrent but once the wet weather set in it had little to no effect at all. Snails of all sizes were happy to cross the shells to reach the juicy reward of seedlings that lay at the centre. The seedlings protected by the crushed eggshells were almost completely devoured and I wonder whether the difficulty in crossing the egg shells made the snails and slugs want to eat as much as they could before making the return journey.
Aluminium can defence
I thought this one up all on my own, perhaps I watched one too many movies involving castles with turreted defence walls. The sharp edge of the aluminium can should be too sharp for the snails and slugs to cross.
To make this you simply take an aluminium soft drink can and cut the top and bottom off with a pair of scissors, then cut the can open lengthways. Cut triangles out of the top of the can to create a jagged edge, you may want to wear a thick pair of gardening gloves to protect your hands. I used four cans, slightly overlapped, to create a ring around my seedlings and secured them against the wind with wire that hooked over the top edge of the aluminium and into the soil.
Did it work?
Nope. The snails quite happily traversed the top of the sharp aluminium edge, not once but twice, first over and in during the night and then out again before sunrise and continued to do the same night after night.
I have read that caffeine may act as a neurotoxin is slugs and snails destabilising the mollusks’ heart rate and leading to death.
I started by brewing coffee in a stove top percolator, then sprinkling the used grinds liberally around the seedlings. The used grinds have a reading of about PH 6, which is acidic, this doesn’t really have any bearing on the experiment but since discovering my garden soil had become very alkaline I like to know the PH level of anything I add to my garden.
Did it work?
Nope. This is unsurprising really as used coffee grounds contain little caffeine. Don’t throw your coffee grinds in the bin just yet though as they are still very useful in the garden. I have read that they are an excellent soil additive containing magnesium, calcium, potassium and other trace minerals, they make a good ingredient for compost, containing about 2% nitrogen, and are suitable for your worm farm.
Fairly self-explanatory, I needed unprotected seedlings to see whether the other methods were working or whether the snails were just un aware of all my potted up seedlings.
Did it work?
Surprisingly, for the first week or so of the experiment these seedlings were just as intact as all the others. I think this may have been partially due to the smell from the coffee grounds and garlic masking the scent of the seedlings and the fact that I have never grown seedlings in these pots in this place in the garden before so the snails and slugs took a while to fully explore and find the plants. The other surprise was that at the end of the experiment the unprotected seedlings actually had more leaves left than the egg-shell, coffee grinds and garlic protected seedlings.
The copper barrier repels slugs and snails by use of a tiny electrical charge naturally created within the copper face
I bought a commercially made copper adhesive tape. The tape I bought had an adhesive backing so applying it was as simple as peeling off the backing paper and sticking it around the edge of my pot. It is recommended that you stick the copper to the exterior of your planting containers to prevent any copper leaching into your garden soil and applying a wide enough band to prevent snails and slugs from looping their bodies up and over the top of the copper and last but not least check that there are no twigs, grasses or other plants reaching over the edge of the pot that may act as a bridge completely bypassing the copper. Another tip is to clean the copper with vinegar if a heavy patina builds up as it may reduce the effectiveness.
Did it work?
Yes!! My experiment only lasted a month so it is still too early for me to determine how long the copper stays effective but even if it needs to be replaced occasionally it is still so far the longest lasting method I’ve tried. The copper tape only works if there are no snails or slugs hiding within the perimeter before you apply it, so it is best for new garden beds, newly cleared garden beds or pot plants.
Once the snails found the seedlings it seemed they were determined to cross any barrier in their way, most probably helped by the fairly persistent rain that set in towards the end of the experiment. The only method to work 100% was the copper tape, although my experiment only ran for one month.
I would say the biggest draw back to most home-made deterrents is the rain, which is also when snails and slugs become most active, another draw back is the frequency with which home-made remedies need to be re applied, sadly life often gets in the way of gardening time and it can be difficult to get outside every time the rain stops to re spray and re sprinkle different deterrents.
You may find success with some of the above mentioned methods, you never know until you try, but a strong defence is best teamed up with a strong attack so with this in mind my next post will cover snail and slug traps.
“The only thing that two gardeners ever agree on is what the third gardener does wrong.” – Tony Avent