Using Lime in the Garden Against Snails and Slugs

How Does Lime Work?

This method relies on the corrosive effect of lime and on the fact that it absorbs moisture.

For these reasons, snails avoid crawling over lime. If they did, they would lose a lot of mucus and, in the process, vital body fluid.

Some people also believe that a snail’s sole or foot is injured as it tries to cross lime.

So, even if a treat is waiting on the other side, snails will not attempt to go across.

Types of Lime Used in the Garden

Calcium Carbonate

(Also known as agricultural lime, garden lime, aglime, agricultural limestone.)

Calcium carbonate is used to increase the pH level of acidic soils and as a mineralizer on sandy/lean soils.

It is less corrosive than other lime variants, so is even approved as a food colorant. It is relatively harmless to handle.

Calcium carbonate is often used in conjunction with magnesium: magnesium lime (CaMg).

Video: Lime in the Vegetable Garden

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Typical Garden Lime

Pelletized Garden Lime	Garden Lime
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Calcium Oxide

(Also known as quicklime, burnt lime.)

Quicklime is made from calcium carbonate.

It is very irritating and corrosive.

You should therefore avoid inhalation at all costs.

Contact with the eyes may cause blindness, so always wear safety goggles.

Wearing gloves is also strongly recommended.

Due to its health risks, quicklime is not normally used in agri- or horticulture.

When calcium oxide comes into contact with water, calcium hydrate is formed.

Calcium Hydrate

(Also known as slaked lime, hydrated lime, caustic lime, builders’ lime, pickling lime.)

Calcium hydrate is also corrosive and irritating, which is why you should always take steps to protect your skin and eyes when using it.

In horticulture, it is sometimes used as a fungicide.

Calcium Cyanamide

(Also known as nitrolime.)

Used in agriculture as a fertilizer, calcium cyanamide slowly releases nitrogen (nitrate) into the soil.

In contact with water, cyanamide is formed.

Calcium cyanamide is poisonous and damages fungi and all organisms in the soil, including eggs and young slugs and snails.

Nitrolime is very harmful even to human health.

It is highly corrosive and, especially in combination with alcohol, it can cause severe damage: shortness of breath, dizziness, and damage to the skin.

You should therefore never use it before or after alcohol consumption.

For these reasons, extreme caution is required when handling calcium cyanamide.

If related health issues are suspected, seek medical advice immediately.

Furthermore, it is a hazardous substance that can contaminate ground- and surface-water.

How to Use Lime Against Slugs and Snails

Sprinkle ordinary garden lime or magnesium lime around your plants and beds to build protective barriers.

The extremely water-absorbing effect should deter all slugs and snails.

Wind and water, however, quickly make the barrier ineffective.

This is why you should also sprinkle threatened plants or beds with a broad, thick ring of lime. A combination of lime and sawdust is possible.

You should ensure that there are no bridges or gaps, otherwise they will be exploited by hungry snails and slugs.

Since the deterrent effect is lost after contact with water, it needs to be spread again after rainfall.

Make sure that you do not overuse lime so that the pH value of the soil does not rise too much.

Some plants are susceptible to changes in pH levels.

When using lime, always wear gloves, respiratory protection, and goggles.

Only by taking these precautions can damage to health be avoided.

During application, the weather needs to be as calm as possible, so that the lime does not evaporate in all directions.

If you plan to use calcium cyanamide, make sure that it does not get on plant leaves or seeds because it will damage them.

You should also use it at least three or four weeks before sowing or planting, otherwise it will harm your seeds and plants.

Products must be stored in a safe place so that they are out of the reach of children and pets.

Advantages of Lime

One benefit is the mineralizing effect of calcium carbonate/garden lime.

Lime also allows you to adjust pH levels.

Additionally, if you use lime in your garden, the composting processes in the soil accelerate.

In the case of nitrolime, effectiveness against snails and slugs has been shown.

Disadvantages and Dangers

With the exception of calcium carbonate (garden lime), lime poses significant health risks.

You need to wear protective clothing at all times, and there is a risk to children and pets.

It is not known how effective the products are against snails and slugs.

Protecting beds and single plants requires regular work by subsequent sprinkling and control.

With rain or irrigation, the protective effect of lime is lost, meaning that this method is ineffective when most needed.

Lime also loses its efficiency during damp nights and mornings.

Nitrolime kills not only snails, slugs and their eggs, but also brings the entire soil life out of balance. It is a dangerous poison.

Using poison in the garden always has harmful side effects.

There are not only health risks, but contamination of the ground and surface waters can also occur.

So, the best thing is not to resort to calcium cyanamide.

Conclusion

Garden lime is effective in getting rid of soil acidity, but it is not a good choice in the fight against slugs and snails.

It should only be used in emergency situations as there are easier and less dangerous means to fight slugs and snails.

Health risks are not to be underestimated. Nitrolime, especially, is a poison that does not belong in the garden.

Soil health is also threatened, even if simple garden lime is used.

In addition, some plants do not tolerate high pH levels; for example:

• carrots
• celery
• fennel
• azaleas
• rhododendrons
• heather
• hydrangeas
• and many more.

So, it is better to try something else first.

On this website, you will find many ways to control slugs and snails.

Commercial Products and Prices

Garden lime e.g. dolomitic lime is available for about 0,50-1 $/£/€ per pound (~0,5 kg).

Calcium hydroxide is expensive and costs about 5–15 $/£/€ per pound (~0,5 kg).

A 20-pound (9 kg) bucket of quicklime costs about 10 $/£/€.

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Garden Lime Products

Pelletized Garden Lime	Garden Lime
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Alternative Slug and Snail Barriers

Mechanical barriers are good alternatives to barriers formed by garden lime.

Slug fences are durable, suitable for protecting large beds, and need no maintenance.

They provide a long-term solution and are less labor-intensive than lime.

You will find more information here:

Slug fence test	Slug barriers

To protect individual plants, special slug collars can be used.

Also, garden cloches can protect seedlings and young plants.

Furthermore, the anti-slug paint Schnexagon will keep slugs out of beds and greenhouses.

This repelling coating sticks to almost all materials and can be painted on quickly and easily.

Finally, there are other materials that work in a similar way to ash as a deterrent due to their dryness or saltiness.

One possibility, for example, is to use salty sheep wool against snails.

You will find more information here: mulch materials against slugs

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Slug control recommendations

Copper Mesh Fence	Slug Fence Set: Medium – 6m²	Sheep Wool Pellets
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Last update: July 18, 2019

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