The idea of deterring slugs with plants comes up again and again. To achieve this, one should plant strong-smelling herbs as a protective wall around endangered vegetable and flower beds.
In addition, it is recommended to use plant sap or plant liquid manure as a slug repellent.
In principle, these measures should be viewed critically because slugs are often not impressed by them. Scientific evidence is still lacking.
Nevertheless, these methods can be a good supplement to other measures, and occasionally, they are successful.
Here you can find out which plants are recommended for a protective wall and which can be used to make a brew or slurry.
There are some plants that seem to have developed a natural defense against slugs.
These include, for example, strongly scented herbs. They contain essential oils and secondary plant compounds that deter predators.
In theory, these herbs should be planted around threatened plants. Then they should be able to reduce the attractiveness of other plants with their scents and even repel slugs.
In practice, the successes are rather small. The method can by no means be described as safe.
These herbs are recommended, for example:
Real camomile
Real lavender
Rosemary
Thyme
Sage
Sea fennel
Hyssop
Horseradish
Lemon balm
Lovage
Elecampane (Origanum)
Winter savory
Chives
Curry herb (Indian strawflower)
Borage
Nastrutium
Savory
Mustard
Boar’s rue
Garden cress
Valerian
Garden chervil
White clover.
Onions and garlic are also said to be useful in protective strips.
One advantage of all these plants is that they are relatively resistant even to slugs. Only young and weakened plants are sometimes attacked. So at least here the harvest is assured.
One problem is that the herbs release their scents mainly when it is warm and the sun is shining. So on rainy days and also at night, when slugs are particularly active, the scent defense is rather low.
In addition, site conditions such as soil texture play a role in the amount of scent produced.
Here you can find more information about slug-resistant vegetables and herbs.
In addition, some flowers are said to deter slugs and snails, and there are even special seed mixtures and seed bands that promise to do so.
With plant decoction and liquid manure against slugs and snails
The difference between a plant decoction and a plant liquid manure is the way it is made. A decoction is usually a hot extract, and liquid manure is a cold extract.
Plant decoctions are made like a kind of tea and can then be used immediately. On the other hand, you make a plant decoction over a period of several weeks before you can use it.
Using a plant decoction
To make a decoction, leaves and/or stems are first boiled in water for a few minutes – depending on the hardness of the parts used, for around 5–20 minutes.
Afterward, the hot decoction is left to infuse and cool for a few minutes before it can be applied directly.
As a rule, the decoction is now sprayed over the threatened plants using a spray bottle. This application should be repeated regularly, especially if it has been washed off by rain.
Elder, ivy, pine cones and wormwood are also said to be suitable.
If you have these plants available in your garden, you can just try it out. You can also combine them.
You can also experiment with the ratio of water and plant parts.
A disadvantage of this method is that some plants dislike being sprayed.
In addition, you should not spray vegetables before harvesting, as the taste can change. Cucumbers, for example, can become bitter.
The same also applies to the use of plant manure.
Liquid manure is usually prepared in such barrels.
Plant manure against snails
The use of nettle liquid manure as a plant strengthening agent is widely known. The nettle leaves are fermented in plenty of water. Depending on the ambient temperature, the preparation time varies from 10 to 30 days.
When the liquid manure is ready, it begins to stink. However, nettle manure is not supposed to help against snails.
There are other liquid manures that are not supposed to be tasty to snails. The following plants are recommended again and again:
Yarrow
Tomato shoots and leaves
Worm fern
Blackcurrant
Here, too, you can mix different plants and add representatives from the brew list above.
Lavender is said to deter snails as a hot and cold extract.
In contrast to hot extracts, liquid manures are often not sprayed directly onto the plants but added to the watering water or used directly for watering.
Because of the nutrients contained in the water, liquid manure also serves as a biological fertilizer.
Conclusion
So far, there are no scientific studies that could prove the effect of plants against snails.
The only study that could prove an effect was on coffee against snails. But its use with coffee is questionable because caffeine acts as an insecticide and is also said to inhibit plant growth.
Nevertheless, it can’t hurt to try it with a brew and/or liquid manure. It has been proven that many plants have a natural protection against slugs and are not attacked by slugs.
If you succeed in transferring this protection to other plants using water extracts, you would have the perfect slug repellent.
Biodiversity can also reduce slug pressure.
If you have had positive or negative experiences on the subject of “plants against slugs”, please leave a brief comment. Then other gardeners can also benefit from your experiences.
After all, it is always a good idea to cultivate as many herbs as possible in the garden. This promotes biodiversity and attracts more natural enemies of slugs and snails.
Therefore, it is definitely worthwhile to border vegetable beds with wide strips of herbs. The kitchen will also benefit from having plenty of herbs available.
Alternatives
If you really want to make sure that vegetable beds are safe from slugs, then it is worth purchasing mechanical barriers.
A raised bed or potted plants can also be protected against slugs with copper tape. Copper does not keep out all slugs, but at least a large part of them.
Fresh sheep wool is also a viable alternative because it contains salt and the fine hairs successfully repel snails. However, it also loses its effectiveness over time due to rain.
But it is the only mulch material that was convincing against slugs in the test.
