Do Coffee Grounds Deter Slugs?

Due to the harmful chemicals in slug pellets, many gardeners have turned to natural remedies for repelling slugs. One tried remedy is using coffee grounds, but do coffee grounds deter slugs? Does it work? And if so, how can we use it to keep our plants free of slugs?

The Quick Answer

Do Coffee Grounds Deter Slugs?

Coffee grounds can deter slugs. If you’re lucky to have a coffee machine at home, sprinkle used coffee grounds around plants that slugs seem to like to deter them.

Why Do Slugs Not Like Coffee Grounds?

Coffee has a bitter smell that is quite pleasant for most humans. But for a lot of animals this smell is unpleasant and can deter them from certain areas. One pest that is deterred by coffee is the slug.

The reason for slugs’ dislike of coffee is actually believed to be because of the caffeine it contains. So, now that we know that slugs are deterred by the use of coffee, let’s look at the different ways that we can utilise this knowledge. 

How to Use Coffee Grounds to Deter Slugs

Using coffee grounds to get rid of slugs in your garden is an easy process. It is better to use used coffee grounds rather than fresh coffee grounds. This is because it both smells stronger and has more extracted caffeine, so it becomes more off-putting for the slugs nearby.

All you need to do with these used coffee grounds is sprinkle them over the soil of plants you want to keep safe. This can be in flower beds or in pots. As soon as slugs come into contact with soil that contains some amount of caffeine, they will be driven away.

Coffee grounds can also actually be quite good for your plants, as long as you don’t use too much coffee, these grounds can help to provide a good source of minerals and nitrogen for the soil which can then help the plants to grow. 

People have also sprinkled coffee grounds around the perimeter of their garden to keep slugs from trying to get in at all. This, in theory, works as slugs are deterred by the presence of coffee.

Sprinkle Coffee Grounds to Deter Slugs

How Do You Make a Caffeine Spray for Slugs?

Caffeine can actually kill slugs. Unlike coffee grounds which deter slugs through smell, caffeine can be lethal which is why it makes for the perfect garden spray. Here’s how to make and use a caffeine spray for slugs:

  1. Make Strong Coffee
    You need to make the strongest coffee you can. If you have a coffee machine then running water through ground coffee twice can give you maximum extraction of caffeine.
  2. Mix With Water
    Once you have made your coffee, mix it with equal parts water to coffee. This will make it easier to spray as the coffee grains can clog up spray bottles otherwise.
  3. Get Spraying
    Spray liberally around the plants that are impacted by slugs.
  4. Continue to Reapply
    You must then continue to reapply every few days – especially after rainfall which can wash away the caffeine from your flower beds.

The other option is to not bother making a spray at all. Instead, make an extra cup of coffee in the morning and share that with the slugs in the garden. All you need to do is pour the coffee around the plants that seem to be getting attacked by slugs and you’ll give that plant it’s own caffeine barrier.

What Other Pests Does Coffee Deter?

As mentioned earlier, slugs are not the only animal that dislikes the strong smell of bitter coffee. Using coffee to deter slugs has a number of benefits that include deterring others pests including those from the list below. 

Snails

Snails are pests because, like slugs, they will eat your plant. Another similarity with slugs is that they also do not seem to like coffee and will be driven away if they come into contact with soil that has been treated with coffee grounds. 

Get Rid of Snails

Squirrels

Squirrels can cause a lot of damage in your garden, but they too can be easily repelled using coffee grounds. The method of repelling is the same, sprinkle the coffee grounds on soil as usual, and the strong smell can deter squirrels from quite a decent area around the coffee.

If you want to further your efforts to deter squirrels, make sure to wet the coffee grounds ever couple of days to keep the smell strong. 

Ants

Ants can become pests quite easily and they also protect other pests, mainly aphids. Driving ants away with coffee requires nothing extra than what you do to repel slugs with coffee.

The smell of the coffee will confuse ants and it will disrupt their scent trails. Ants make scent trails between their nests and nearby sources of food. Coffee messes up these trails so the ants cannot properly navigate around. The result is that the ants will usually move their nest away from the strong coffee smell. 

What Else Deters Slugs?

Whilst coffee grounds are very effective at deterring slugs, it is always a good idea to combine your repelling methods to give your garden even more protection from slugs.

Here is a list of some other simple things that you can do to keep slugs away from your plants:

Rough Terrain

Because of the way that slugs travel, certain terrains are difficult for them to cross. These terrains include gravel, slate and mulch. They will avoid cross these terrains as they are uncomfortable and can sometimes harm them.

Putting pieces of gravel, slate or mulch, on top of the soil of disturbed plants will drive slugs away because, often enough, the benefit does not outweigh the cost of crossing this terrain. 

Pet Hair

Using pet hair may seem like an odd thing to do, but it does work. If you have a dog or a cat, get some hair clippings for your pet and sprinkle them around plant pots and flower beds which are frequented by slugs.

The presence of this pet hair will cause the slugs to think that predators are around and so they will vacate the area. This method also helps to deter squirrels. 

Plant Repellent Flowers

A nice way to keep slugs at bay is to plant things that they dislike. This method is most effective if you intersperse the repellent plants (we’ve listed 7 here) with the ones that you want to keep safe.

Slugs dislike certain plants because of their smell or their textures. These are some plants that will help you to keep those slugs away, you can use lavender, hydrangeas and geraniums. 

Geraniums Deter Slugs

Final Summary

To summarise, coffee grounds can deter slugs because slugs do not like to be in contact with soil that has been exposed to caffeine.

Simply sprinkle used coffee grounds on top of the soil to keep slugs away from these areas. Coffee grounds will also help to deter other pests including squirrels and snails.

Other methods of repelling slugs include using difficult terrain for them to cross and planting flower that repel slugs, these flowers include geraniums and hydrangeas. 

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