Household ammonia is reported to be great for controlling slugs. Some people spray the slugs directly and apparently it kills them. Others spray plants so slugs stop eating them. Spraying soil is also a common method of controlling slugs and snails.
Do these methods work?
Ammonia is a strong cleaning agent and it surprises me that spraying it on plants will not harm them, but maybe the dilution used is low enough to prevent damage. If that is true, what is the ‘safe’ dilution ratio?
What is Household Ammonia?
Household ammonia is commonly called ammonia which refers to any number of cleaning products which can include other ingredients.
True ammonia is a gas at room temperature with the formula NH3. It is also called anhydrous ammonia. Nobody uses this in the home or garden.
When ammonia is dissolved in water it forms ammonium hydroxide which is the same as household ammonia and it contains 5-10% ammonia. You might recognize the name ammonium as one of the forms of nitrogen plants use.
I tried to buy some of this a few months ago and couldn’t find it. The only products I found had other ingredients added, like coloring agents, smell blockers, soap. I guess companies are trying to make a better cleaning product that does not smell so badly.
What do these extra ingredients do to plants and slugs? I have no idea. Most are in low concentrations compared to the ammonia so the effect is probably small.
Properties of Ammonia
The pH of household ammonia is between 11 and 12, depending on concentration. This is a very alkaline solution.
The other property that is important for this discussion is the stability of the product. Remember that household ammonia is water and ammonia. The latter is a gas at room temperature and as such it evaporates quickly. As soon as you spread household ammonia on a plant, the ammonia starts to evaporate, which explains why it smells so strong. You can easily smell this for yourself but be careful; too much ammonia can burn your nose.
I also prepared a video where you can see my slug actors reacting in real time to the effects of spraying soil, leaves and directly spraying the slugs.
If this video does not play try this link; https://youtu.be/79FITnxcViU
Diluted Solutions of Household Ammonia
All of the techniques for getting rid of slugs suggest a dilution ratio but the product being used is not often clear.
For example: “use diluted ammonia (5 to 10% solution) “, which comes from a government site.
If we take a literal interpretation, you should use household ammonia right out of the bottle since its already a 5-10% solution of ammonia. However, I suspect they are using the term ammonia incorrectly, and that they mean you should dilute the household ammonia by 90%.
Many of the suggested mixtures on the internet suffer from this problem.
Drop Slugs in Ammonia
One way to deal with slugs is to physically collect them and drop them into some household ammonia. A 10% solution will do the job.
I have no doubt this works. Apparently soapy water also works.
Spray Slugs with Ammonia
Picking slugs is not everyone’s cup of tea, so some prefer to just spray them right on the plant, or as they travel along the ground. Lots of reliable online sources and even some YouTube videos confirm that this works, which should be no surprise given the high pH of household ammonia.
But what concentration should you use?
A concern with this method is the effect on plants. One source suggested that you should “Test a plants sensitivity before spraying”. Are you going to test every plant in the garden? I could not find any information about plant sensitivity to household ammonia.
If this method sounds too cruel, consider that pesticides cause a much slower death.
Spray the Plant or Soil
Popular gardening sites suggest that you can spray either the plant or the soil and keep slugs away. An added benefit of this technique is that the ammonia provides a nitrogen feed for the plants.
The common dilution for this technique is a 10% solution (1 part household ammonia to 9 parts water).
Virtually all of the government websites (sites with a edu extension) say that if you use ammonia to control slugs it needs to be applied directly to the slug. They DO NOT promote the idea that spraying plants or soil works.
The problem with this technique is that ammonia evaporates quickly.
I tried a quick test. I spread some household ammonia on a hosta leaf. The smell was quite strong from the evaporating ammonia but it only lasted for about 3 minutes. Admittedly, my nose is not the most sensitive analytical instrument, but even the water evaporated in a few minutes. Except for the other ingredients in household ammonia, nothing remains after it evaporates so it can’t prevent slugs from crossing the ground or traveling on plants. It is highly unlikely that either of these techniques work.
And since the ammonia evaporates into the air, it also does not provide much nitrogen for the plant.
One source suggested that the soil should be ‘drenched’ in early spring. I guess if you apply enough ammonia solution to the soil you will kill newly hatched slugs and maybe even eggs when the ammonia contacts them. This would take a lot of ammonia for even a small garden.
Getting Rid of Slugs and Snails
I have written extensively about this topic. Most DIY techniques do not work, or have a limited effect. Slug bait works best and is relatively safe.
- Eggshells Control Slugs – Do They Really Work?
- Getting Rid of Slugs With Coffee Grounds
- How To Get Rid of Slugs With Beer
- How to Get Rid of Slugs With Copper
- How to Get Rid of Slugs with Diatomaceous Earth
- Does Cornmeal Kill Slugs and Snails?
- Slug Bait – Metaldehyde vs Iron Phosphate