What is potassium soap for?

We like to talk about all the products that we can use to have plants in perfect health. Although with chemicals or minerals you have to follow a series of rules to avoid problems, they are very useful when our pots or our garden is being affected by pests. However, the natural ones are very effective in preventing plants from having to deal with the multitude of insects that are always on the lookout, and can even fight them .

One of these remedies is potassium soap , an ecological and very cheap insecticide that acts by contact and not by indigestion, thus preventing the sap from becoming intoxicated.


  • 1 What is potassium soap?
  • 2 Why use it?
  • 3 What is it for?
  • 4 What is its mode of action?
  • 5 How is it used?
  • 6 When should plants be treated with potassium soap?
  • 7 How to do at home?
  • 8 What are the benefits of potassium soap?

What is potassium soap?

The one that is considered by many as the best insecticide that currently exists, is a compound formed by potassium hydroxide (KOH), oil (either sunflower, olive, clean or filtered and recycled) and water . After the saponification process, that is, when the alkali (potash) reacts when mixed with water and fats (oil), we can use potassium soap to eliminate and prevent pests from our plants.

Why use it?

Today we are using many synthetic products , that is, chemicals. These can come in very handy at any given time, such as when we have a plague that is destroying our crops or when a fungus is weakening our plants, but they have several drawbacks and that is that they are toxic to humans . If even a drop of chemical insecticide falls on a wound or cut, it can cause us a lot of damage, and that is the least that could happen to us. In addition, they are very harmful to the environment.

But with natural products , although it is true that you have to read the label and use them as directed, the reality is that they are not dangerous for us humans or for flora and fauna , except, of course, for those pests that we want to eradicate. For this reason, it is very important to have these as the first option, as this also contributes to strengthening the defense system of plant beings.

All in all, potassium soap is a good insecticide : it is ecological, it does not attack other beneficial insects such as bees, and as if that were not enough, it can be reused as fertilizer, because when it decomposes it releases the potassium carbonate, which can absorb the roots. It can be stored easily, and most importantly, it is not harmful to people.

What is it for?

Eliminate aphids with potassium soap

This insecticide is used to maintain the health of your plants in perfect condition, eliminating the insects that cause so much damage to them, which are aphids, whiteflies and mealybugs . It is said that it is even effective as a fungicide, which is not bad at all, don’t you think?

Its price is about 10 euros a bottle of 1 liter. It may seem like a lot, but in reality you add so little that that amount goes a long way.

What is its mode of action?

Potassium soap acts by contact . This means that when the parasite lands on an area where we have put the soap, or if it has been covered by it, what will happen is that the cuticle that protects it will soften, causing death by suffocation.

As a consequence, it is very important that the product is applied to the entire surface of the plant , especially to the most tender parts since these are the most vulnerable areas.

How is it used?


To use it correctly you have to dilute 1 or 2% potassium soap in water , and apply it by spraying the leaves, thoroughly soaking both the upper and lower sides. This must be done in the hours of less insolation to prevent the sun from burning the plants.

When should plants be treated with potassium soap?

As it is a product that does not leave residues, in order to have a more lasting effectiveness, we have to carry out the treatment at sunset, and only if it is not raining or windy . In the event that we have the plant in a pot, it will be highly advisable to have it protected once we have treated it with potassium soap; in this way, we will make sure that it will give you the desired effect.

It is very possible that we will have to do several treatments, so we will treat it every 15 days for three to four months.

How to do at home?

If we want we can make potassium soap at home, but it will be essential to use gloves and protective glasses to avoid problems. Once we have it, we will also need potash hydroxide, water and sunflower oil. You got it? Well, now, follow this step by step :

  1. The first thing to do is mix 250ml of water with 100 grams of potash hydroxide.
  2. Then, we heat 120ml of oil in a water bath.
  3. Next, slowly add the oil to the mixture of water and potash hydroxide.
  4. Then, the whole mixture is placed in a water bath and stirred for one hour.
  5. Finally, 40 grams of soap mass must be mixed with 60 grams of warm water. Stir and voila!

What benefits does potassium soap have?

Green grapes

Being made by saponification with vegetable oils, it is an ecological product that does not harm the fruit and is respectful of the environment , since it is biodegradable . In addition, it is harmless to people and animals , so it is a highly recommended insecticide when you have children or animals.

What is potassium soap for?

Leave a Reply

Scroll to top
%d bloggers like this: