Finally, a home remedy that puts slugs to flight. Or not? I have tested coffee grounds against slugs and tell you what it really brings!
Who has a small garden like me and cherishes it with much love, knows the problem: slugs!
They have it on lettuce, cucumbers and actually everything, which also tastes us. Within a very short time, heads of lettuce are nibbled and slimy.
Totally annoying when you put so much time into growing and caring for your plants.
There are a few ways to combat slugs in the garden. My favorite in my natural garden are home remedies that do not negatively affect the creatures in the soil and keep the soil healthy.
I think little of poison in general, but if there is no other way to the wedding in June, then a little slug pellet.
When my mother told me the other day that coffee grounds are supposed to help against snails, my ears perked up. After all, everyone has coffee grounds to spare, they don't have to be bought separately and are a natural remedy.
But is it really true that coffee grounds work against slugs or is it just a rumor? I have tried it out for you.
Table of contents
What does coffee grounds do to snails?
Snails do not like the smell of coffee or caffeine. Coffee grounds help against snails because it stimulates them to produce more mucus. Often this harms the animals, which is fatal for them. Coffee grounds contain bitter substances. They provide a very special smell that snails, cats and ants can not stand.
From studies on mollusk neurons, caffeine releases calcium from the cells' internal stores and increases the length of action potentials.
Action potentials help to transmit stimuli. If this takes longer than usual, there is a higher consumption of oxygen and energy. The slugs collapse.
Coffee powder is a great barrier layer to sprinkle around your plants. It keeps slugs away. And on top of that, the supposed waste product acts as a natural fertilizer for many plant species.
Another advantage is that the smell of coffee attracts earthworms, while it drives away slugs. Earthworms loosen the soil and make your plants grow better. A soil that contains a lot of earthworms scores with a rich harvest.
Coffee grounds against snails: What studies say
A US study from 2002 showed that nudibranchs are deterred by coffee concentrate and can even kill them at higher concentrations. A caffeine content of 0.1 percent - i.e. the same as in a strong espresso, already ensures the first reactions of the mollusks.
From 2 of a 2-percent caffeine solution should put an end to the animals. The researchers assume that caffeine acts like a neurotoxin on snails.
When to use coffee grounds against snails?
A few small holes in the lettuce are not the end of the world. In the first place, you should simply collect the pests and dispose of them.
On a small scale, snails are even healthy for the garden. When they are very small, they serve as food for birds and hedgehogs and eat dead animals and decaying plant parts. However, if slugs occur in large quantities, then the balance is disturbed.
Not all snails are harmful. In fact, you should be happy to have slugs in your garden. They feed, among other things, on the eggs of the slug. What I want to say is: Only use tools when you really have a lot of slugs in your garden.
Have you ever seen light brown nudibranchs that have a spotted pattern? These are tiger slugs (tiger snails). You should definitely leave them in the garden - they are the natural enemies of red slugs. Their favorite food is the eggs of slugs.
How to use coffee grounds as fertilizer!
How you can use coffee against slugs
There are two ways you can use coffee against snails. However, the following applies to both: coffee is water-soluble. So the caffeine will be washed away in heavy morning dew and rainfall.
You need to repeat the treatment.
Dry coffee grounds against snails
Pure, dried coffee grounds are a deterrent for snails. If the snails appear in large quantities and are properly hungry, then they will not be deterred.
Unless a snail is crawling over an exorbitant amount of coffee grounds, it is virtually unlikely that ingesting caffeine will be fatal. They get used to the scent over time.
Still, it's worth a try.
Always dry the coffee grounds before using them. If you collect them wet and put them in the garden later, they may start to mold. Alternatively, scatter them in the garden directly after your morning cup of coffee.
You can mix coffee powder with garden soil and then sprinkle it on the bed. So you have a natural fertilizer and slug repellent in one.
But you can also sprinkle the coffee grounds in a ring around individual plants that are particularly affected like lettuce.
If you want, instead of coffee grounds against snails, you can try coffee powder. The powder has a higher concentration of caffeine. Whether it's worth it to you, you have to decide for yourself. After all, coffee is a relatively expensive luxury food that consumes a lot of resources.
Coffee extract against snails
In the University of Nebraska study, the substrate or leaves of plants were sprayed with caffeine solutions at varying concentrations.
It was found that
- Snails from a caffeine content of more than 0.1 % are deterred
- they are killed from 1 % caffeine content
Depending on the type of coffee, the caffeine content varies greatly. Arabica coffee beans have a caffeine content of approximately 0.8 to 1.4 %. Robusta coffee comes to 1.7 to 4 %.
However, as the coffee beans are diluted with water, the caffeine content decreases. There is still about 0.06 to 0.1 % of caffeine in boiled coffee.
So if you want to use coffee brew to combat slugs, you'll need to brew a decent strong coffee.
The catch is that with such a high concentration of caffeine, other creatures in the garden can also be harmed.
If you want to spray the plants, be careful not to get too much highly concentrated coffee on the soil. Let the coffee cool, pour it into a spray bottle and apply it to the plants.
You should do this in the evening when there is no more direct sun on the plants.
What is the best way to use the coffee?
To keep slugs away from your delicate plants, we recommend using coffee grounds as a deterrent. Sprinkle a ring of coffee grounds around the plants.
The scent is so strong that it creates a barrier for the snail. However, you should remember to renew the coffee grounds ring only once a year. Caffeine can affect soil health if used in excess.
Pour undiluted cold coffee directly on the soil around your plants to naturally repel slugs. Exclude flowering plants as it can also deter pollinators!
To protect your coffee from the wetness of rain, keep a close eye on the weather. Refrain from spraying plants when it is already raining, has just rained or rainy weather is imminent.
It is difficult to make concrete statements about which plants could be damaged by coffee residues and to what extent they tolerate it. In other words, try it out for yourself!
Caution: Too much caffeine harms all living things
The fact is that caffeine is a neurotoxin. In highly concentrated quantities, it causes great damage. You're not only fighting slugs with coffee, but also beneficial insects like slugs with houses, earthworms, and a whole host of insects. Likewise, many plants are sensitive to a large amount of caffeine.
What I learned from my self-experiment
But does it really help? I am very curious about my test. Are you too? Here comes the info I learned in the self-test.
For the test, I collect a week's worth of coffee grounds. That makes a small bucket full. I dry the grounds in the sun so that I don't have to use them all at once.
The weather is nice and should stay that way for the next two days. The perfect time for the experiment.
The lettuce plants all get a ring of coffee grounds about 5 centimeters high. Between the herbs and other plants I spread the coffee grounds with my fingers and a small shovel.
I also sprinkle a line around the garden. Can not hurt, whether it helps, I do not know.
Now we have to wait.
After three days the first control.
At first glance, I can not see any snails late in the evening. But in the morning it becomes clear that nevertheless bite marks can be seen on the lettuce. However, they are much less than on the days without coffee grounds.
But this could also be due to the fact that the soil is quite dry, because it has not rained for a long time.
On the fourth day, the weather turns. When it rains, and immediately after, coffee grounds do not help. You have to keep re-sprinkling it around the plants. I used a mixture of fresh coffee and used coffee grounds to intensify the effect.
On the fifth day, as soon as the soil is reasonably dry, I spread a new slug fence of coffee.
When I go out into the garden early in the morning, I actually see a snail sitting right on top of the coffee grounds. She's probably happy to get some free coffee in the morning. Feeding her in addition was actually not what I had planned.
Let's see how it develops further. As soon as I have new findings, I will record them here!
Coffee grounds provide beautiful and well-groomed hair!
My conclusion
Coffee grounds against snails works well at first glance. But apparently they get a little used to the smell. Because I keep finding slugs that don't seem to mind the coffee. But the smell of coffee beans is at least a bit of a deterrent. And since you have coffee grounds at home anyway, it can't hurt.
Worms are also happy about it, which can never be a mistake. In addition, coffee grounds act as fertilizer for some plants. It's best to just try it yourself before the coffee grounds end up in the trash.
Tip: Rosemary and thyme placed around the bed, should keep slugs away. It's worth a try!
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