What is potassium soap for?

Potassium soap

Image - Guara soaps

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

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

What is potassium soap?

Which is considered by many to be 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 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 handy at some point, such as when we have a plague that is killing our crops or when a fungus is weakening our plants, but they have several drawbacks and they are they are toxic to humans. If even a single 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 indicated, the reality is that They are not dangerous neither for us humans nor for the flora and fauna, except, of course, for those pests that we want to eradicate. Therefore, it is very important to have these as the first option, as this also helps to strengthen the defense system of plant beings.

With everything, 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 compost, because when it decomposes it releases the carbonate of potash, which the roots can absorb. It can be stored easily, and most importantly: it is not harmful to people.

What is?

Eliminate aphids with potassium soap

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

Its price is about 10 euros a 1 liter bottle. It may seem like a lot, but in reality, so little is added that that amount spreads a lot.

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.

Consequently, it is very important that the product is applied to the entire surface of the plant, especially for the most tender parts since those 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, soaking both the upper part and the underside well. This must be done in the hours of less sunshine to prevent the sun from burning the plants.

When to treat plants with potassium soap?

Being a product that does not leave residues, so that it has a longer lasting effectiveness we have to perform the treatment at sunset, and only if it is not rainy or windy. In the event that we have the plant in a pot, it will be highly advisable to keep it sheltered once we have treated it with potassium soap; in this way, we will ensure 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 again every 15 days for three to four months.

How to do at home?

If we want we can make potassium soap at home, but The use of gloves and protective glasses will be essential to avoid problems. Once we have it, we will also need potash hydroxide, water and sunflower oil. You got it? Well, now yes, 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 bain-marie.
  3. Next, you have to slowly add the oil to the mixture of water and potash hydroxide.
  4. Afterwards, the whole mixture is put in a water bath and stirred for an hour.
  5. Finally, 40 grams of soap mass should be mixed with 60 grams of warm water. It shakes and, voila!

What are the benefits of potassium soap?

Green grapes

Being made by saponification with vegetable oils, it is an ecological product that does not harm the fruit and environmentally friendly, Since it is biodegradable. Furthermore, it is safe for people and animals, so it is a highly recommended insecticide when you have children or animals.

What do you think? Interesting, right? 🙂

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  1.   Abalansu Suarez said

    I can mix the potassium soap with the neen

    1.    Monica Sanchez said

      Hello Abalansu.
      Yes, being natural and ecological you can mix them without problems.
      A greeting.

  2.   Fernando said

    Hello Monica, I would like to know what product you could recommend for my peaches and plums, to protect from the cold, a product that is to spray the entire plant, thank you

    1.    Monica Sanchez said

      Hello Fernando.
      Well, I've been looking for information, but I can't tell you. Sorry.
      Products that protect, I recommend the anti-frost fabric which is very good to place (you can buy it at any nursery). But liquid products… I don't know.
      A greeting.

  3.   Luis said

    Hi Monica, I want to know if you can apply it directly on fruits that are full of a white cobweb that makes the fruits not grow and dry out

    1.    Monica Sanchez said

      Hi Luis.
      Yeah right. You can apply it without problems.

  4.   GABRIELA said


    1.    Monica Sanchez said

      Hello Gabriela.

      In principle, 120ml should be enough.