The war being waged between gardeners and slugs and snails is a never-ending one. I have been known to obsessively go out after dark during the summer months with a torch and bucket and pick the critters off my plants, much to the amusement of my family. They are then swiftly dispatched in the lane at the end of the garden to hopefully take up home elsewhere.
Let me introduce you to the main offenders. The common garden snail (Helix aspersa) and the banded snails (Cepaea nemoralis and Cepaea hortensis) are the variety we are most likely to come across. The small, banded snails are particularly fond of my garden in Bath. Slugs come in many shapes and sizes, the common garden slug (Arion hortensis) the large black slug (Arion ater) and the grey field slug (Deroceras reticulatum) and the small but very agile keeled slugs (Milax species). The large black slug also can be found in an orange-brown colour, which you may also be familiar with. There are also aggregates of these species that make identification more difficult, but at the end of the day, most people only want to know how to stop the blighters from eating their garden!
Slugs will tend to not eat any plants that are tough, hairy and bitter. They’ll much prefer soft sweet lettuce to chicory, sprouts over sprouting broccoli, and chrysanthemums over dandelions. They also can’t eat plants that have waxy or hairy leaves, as their tongues can’t scrape away at the surface of these. They are also not keen on anything scented or strong smelling, particularly plants such as Lavender that releases their essential oils and are extremely pungent and unpleasant to the slug.
However, I think in order to know how to fight them you need to understand how they operate and each of these species has a different modus operandi. Slugs remain active pretty much all year round and can feed once the temperature is about five degrees, which means that this winter would have been tough times for them. Snails however hide under pots and anywhere they can find and seal up their openings with mucilage, which dries to a hard shell and glues the shell to whatever they are sitting on. This means they can survive without losing water. Both slugs and snails lay their eggs in batches of up to fifty in holes in the soil, these white eggs are about two millimetres round and take at least a year to hatch.
In order to keep control over these creatures and to ensure that your plants remain un-munched, I have found over the years that it is necessary to use a variety of techniques. I am not a fan of normal blue slug and snail pellets and would not advocate their use; however there are lots of other ways to more effectively deal with slugs and snails without harming other wildlife. Apart from the danger to other animals with pellets, they look unattractive and there are always legions of dead slimy bodies left on the surface of the soil, which can be extremely unpleasant to clear up.
My favoured methods for slugs are multi-layered. I would firstly use Nematodes. This is an organic way of dispatching the slugs via a bug called phasmarhabditis hermaphrodita, which essentially kills the slug. This is simply mixed with water and applied to the soil during the start of the growing season once soil temperatures hit five degrees. I tend to use Nemaslug, available online from Harrod Horticultural and making sure that you use enough for the size of plot you want to treat.
If you don’t want to use nematodes, for newly emerging or newly planted and vulnerable plants I would always advise to use several control methods to address the many ways that slugs in particular use to get at plants. The first would be to use a plastic cloche of some kind over the new plant, or if it’s a small seedling, the top of a large plastic bottle cut off and stuck in the ground with the screw top lid left off to allow air in. Around this I would also use a mixture of a collar of Cornish grit or some sharp sand together with some horse bran, which is very drying and hard for slugs to travel across. If this is applied in layers, it generally does the job of protecting the plant. The common slugs travel across the soil and therefore are prevented by the drying effect of the bran, and if that does not get them, the grit is also extremely hard for them to move on. The keel slugs tend to come up through the soil and so can find their way easily into the cloche, this is where it is worth using a safe pellet such as Growing Success, which I have used for many years and has been known to work effectively in conjunction with these other barriers. It works more slowly than the blue pellets so the slugs or snails tend to crawl off and die elsewhere. Also not pleasant, but the only way if you want them out of your garden.
For pots or containers, some gardeners have found success using copper rings put around the edges of the pots, slugs or snails are unable to attack plants surrounded by one of these copper rings. The copper ring forms a physical barrier around plants and also gives slugs an unpleasant shock-like sensation when they try and cross or climb the copper, caused by a reaction between the metal and the mucus they rely on to move. These are also worth a try and can be found in most garden centres or online via Harrod Horticulture and other suppliers.
There is always the more eccentric approach to use particularly for snails in the evening, which is to remove them by hand as they launch their attack on your plants and then either dispatch them by dropping them into hot water (not my favoured method) or releasing them elsewhere, in my case down the bottom of the road, possibly to attack someone else’s garden! You can also use a beer trap, which can be a jam jar or similar set into the soil and part filled with beer and the pests will drown in the liquid, but make sure to set the jar above soil level so prevent other insects falling in. I have found that with this method and depending on how sluggy your garden is, that you need a lot of these traps and it can be less than pleasant emptying them on a regular basis!
Generally I have found that I simply avoid using plants that I know to be delicious to slugs and snails, particularly in my own garden where they seem to thrive. There are many plants which are resistant to them and unless you have a lot of time on your hands to wage a constant war, which I do not, it’s probably best to give in and leave out delicious delphiniums and scrumptious salvias and avoid the total despair which comes from seeing your plants reduced to shreds overnight.