Gardening Tips

How to make potassium soap

How to make potassium soap

Using products with artificial chemicals to care for plants, both as fertilizers and products to prevent and treat pests, is dangerous both for the plants and for our health, depending on the specific product. Therefore, more and more people choose to use natural products to care for plants, to help them grow and to prevent and treat their conditions.

It is the case of potassium soap, potassium soap or potash, which is an ideal natural product for plant care. If you still do not know it, in EcologíaVerde we will explain what it is and what it is for exactly, how to make potassium soap and the dose to use it correctly, among more details. Learn how to do it and use it and you will see that your plants will thank you.

What is potassium soap and what is it for?

The potash or potassium soap It is a natural and ecological product that is highly effective in eliminating pests in plants, as well as helping to prevent them. This product is obtained thanks to the reaction of the saponification process that occurs when the potassium hydroxide reacts with the oil and with the water.

Basic composition of potassium soap

  • Water
  • Vegetable oil
  • Potassium hydroxide (KOH)

What is potassium soap for?

As we have already mentioned, potassium soap is used to control pests in plants and improve their health. It is especially effective against aphids, mealybugs and whiteflies, but it also treats other types of plant pests and even fungi.

If you are looking to learn more about how to get rid of pests in orchards and gardens naturally, we recommend this other EcologíaVerde article on How to combat pests in organic farming.

How to make potassium soap - What is potassium soap and what is it for

How to make organic potassium soap step by step

If you want to learn how to make natural insecticide with potassium soap or, what is the same, how to make organic potassium soapdo not miss this simple step by step:


  • Rubber gloves
  • safety glasses
  • Kitchen scale
  • Blender
  • Plastic, glass or stainless steel containers to store the soap

Protections are necessary because while the reaction between potash and water occurs, it can damage the skin and sensitive parts such as the eyes if it splashes, so prevention is better. Then once finished it is no longer that aggressive, neither for us nor for the plants but for a variety of pests of these.


  • 120 g vegetable oil (olive, sunflower, corn or canola oil)
  • 20 g of potassium hydroxide (KOH)
  • 20g of water

How to make potassium soap step by step

  1. Put on the protections (glasses and gloves).
  2. Mix the potash with the water and keep stirring, you will see that the temperature increases while the reaction is taking place.
  3. In another bowl or container, pour the vegetable oil you have chosen and heat it in a bain-marie in a saucepan. Let it heat up for a few minutes, then remove it from the heat.
  4. When the two things are at room temperature, mix them together in one of the containers.
  5. You will see that it is acquiring a dark color. When it is more uniform, beat it with a mixer between 2 and 3 minutes.
  6. Let the whipped mixture rest for about 10 minutes and beat again for another 3 minutes, repeat as many times as you need until you get the texture you prefer. However, keep in mind that to use it later on your plants, you will have to mix it with water to dilute it.
  7. You can store it in the container you used to make the last mixture if it has a lid, or you can store it in a plastic or glass bottle.
How to make potassium soap - How to make organic potassium soap step by step

How to use potassium soap: the dose

Now, you just need to know how to use potassium soap on plants correctly. To be as effective as possible it will be necessary to ensure that cover the entire affected plant with potassium soap and insist on the areas that are most affected by the pest to be eliminated. As soon as the insects or parasites that affect the plant come into contact with the organic potassium soap, they will die.

The dose of potassium soap It is very variable and depends on many factors, from the type of pest to be eliminated to the affected plant species to be treated. The most common dose of potash for plants is 1 or 2% of potassium soap in water.

The best way to use it once the dose has been prepared in the water is by spraying it. Remember that since it is about moistening the entire plant, it is best to apply the potassium soap to the plants when the sun is not shining on them, to prevent them from burning.

For best results it is recommended apply potassium soap for 15 days over 3 or 4 months.

Where to buy potassium soap or potash

You may prefer to try the commercial product before getting involved in making potassium soap at home. if you are looking for where to buy potassium soapwe recommend that you go specialized shops in gardening, horticulture and agriculture or, to stores such as large supermarkets where they may have a gardening section. In addition, you can find it both in physical stores and online stores. The price of potassium soap is around €10 for an average 1L bottle.

If you use the commercial product instead of the one prepared at home, remember to follow the instructions on the product packaging and those that the specialist of the store where you purchased it has told you.

We recommend you also read this other EcologíaVerde article on How to make natural insecticides for plants.

How to make potassium soap - Where to buy potassium soap or potash

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