Scatter dry ash around threatened plants and beds to form a protective wall.
The wall should not have any gaps and should be as wide and thick as possible.
The more ash you use, the greater protection there will be.
After rain or irrigation, be sure to renew the barrier because moist and damp ash loses its deterring effect.
Also remove any bridges that might help slugs to bypass the wall.
Advantages
One significant advantage is that ash is available for free to all gardeners who own a fireplace.
It also acts as a fertilizer and benefits the soil as it contains potassium and other vital minerals and micro-nutrients.
Finally, the presence of ash means that composting of other substances is supported and accelerated.
Disadvantages
Ensure that you use only ash from untreated wood, otherwise toxic substances may contaminate first the ash and then the ground.
Ash from old trees can contain heavy metals that should not end up in a vegetable garden, as the toxins could otherwise pass into food.
In flower beds, the use of ash might not cause a problem.
Unfortunately, after a little rain, any protection from ash is lost.
So, be sure to check and renew the ash regularly.
Gusts of wind can also quickly carry away dry ash and create gaps in the barrier.
One significant disadvantage is that the lime content will raise the PH value of the soil and not all flowers and plants appreciate that (e.g. pepper).
So, you should pay close attention to see which plants tolerate ash and which react badly to it.
In addition, some people find ash on flower beds unsightly.
Use only wood ash because other varieties could contain heavy metals such as those used in ink.
Conclusion
The good news is that ash has a repelling effect and tiny slugs and snails are already deterred by a few centimeters of ash-ground.
The significant weakness of this method is that it is not waterproof and therefore requires maintenance.
When it is raining, and slugs and snails are very active, ash does not work to protect the plants.
However, ash is also beneficial as a fertilizer.
If you know which plants tolerate ash and which do not, the application is easy.
However, it is crucial to use only ash from untreated wood, because no one wants to have heavy metals in the garden and therefore in food.
Heavy metals can become highly toxic.
There are more ways to set up barriers for slugs and snails.
Alternative Slug and Snail Barriers
Mechanical barriers are good alternatives to barriers formed by mulch materials.
They are also painlessly efficient and require no further work once constructed.
Slug fences are not cheap, but they are durable, suitable for protecting large beds, and need no maintenance.
They provide a long-term solution and are less labor-intensive than ash and most other methods.