How To Use Potassium Fertilizer To Grow Cannabis


If you are growing cannabis, you need to know that your marijuana plants need various nutrients, which is why they require fertilizers with nitrogen, phosphorous, and potassium, in addition to other minerals such as sulfur and calcium. However, the focus, for now, is potassium. Your weed requires the right amount of potassium to thrive and grow so it can provide you with the buds you want. You need the right amount of potassium, and your pets need it to stay healthy. Therefore, your cannabis plants and any other plants you grow require it too. Let’s talk about the importance of potassium and what it is before delving into how to give it to your plants.

What Is Potassium?

Potassium is a mineral that derives from the soil, especially clay soil. The mineral is essential for the health and growth of any living being, whether it is for animals or plants, and your cannabis plants require the right amount of potassium. In addition, while the cannabis plant is in its flowering stage, potassium is essential for bud development.

The potassium in soil self-regenerates and that process is known as the potassium cycle. Plants soak potassium through their roots, and rain washes away any potassium left in the soil. The potassium washed away finds its way to the nearby lake, pond, or ocean, becoming water vapor. The vapor condenses into rainfall which falls onto the soil, thus replenishing it.

However, in regions with frequent rainfall, the soil may not keep enough potassium, so you need to add more to those plants. Therefore, if it rains a lot in your area, you will need to give your plants potassium chloride or sulfates, which will help them maintain the mineral. But, again, that is something you will need to discuss with a cannabis-growing expert to guide you.

You may not have to give your cannabis plants that much of it if you have a lot of animals nearby, such as birds, foxes, raccoons, or other animals. That is because another way that potassium returns to soil is through animal droppings. So now, let’s talk about why your cannabis plants require this mineral.

Why Do Your Cannabis Plants Need Potassium?

Let’s talk about why your cannabis plant requires potassium, the K in the N-P-K fertilizer. Nitrogen is the N, and phosphorous is the P, which provides their own necessity functions for plants, and the K is for potassium which comes from the Latin “kalium.” Potassium provides sturdiness in plant tissues and strengthens them too.

Additionally, the mineral helps with the plant’s resistance to infections and other diseases and plays a significant part in photosynthesis which helps it synthesize carbohydrates. As a result, potassium stimulates growth in the early stages, and it also keeps the plant safe and resistant to outside elements such as frost. That is why potassium is given to plants and crops to keep them safe from cold weather.

The mineral also helps increase the size and density of buds, and it helps improve water use by making it more efficient. So now, you see why your cannabis plant requires potassium. If your plants do not receive enough of the mineral, they will become deficient, which will cause them to get sick. On the other hand, if your plants receive too much potassium, which is toxic, they will also become ill.

However, like nitrogen and phosphorous, potassium is mobile, so your cannabis plant can take it in from old growth and pass it over to newer development when there is not enough mineral. That is why older leaves at the bottom of the cannabis plant will show signs of potassium deficiency. Naturally, you do not want that to happen. So now, in regions with frequent rainfall, let’s go into detail about how to give your cannabis plants potassium.

The Potassium Requirements In The Early Stages Of Plant Growth

You do not want to feed seedlings potassium or any nutrients during the first three weeks of growth. That is because lack of nutrients helps to promote a healthy root system. When your plant reaches around six inches in height or 15 cm, you can begin to feed it. You will want to give your plant a quarter to a half of the recommended dosage unit until it reaches the vegetative state when you feed it the total dosage. Any weed-growing expert will tell you that, and the best thing you can do is listen to them because you can ruin your plants otherwise.

What About The Potassium Requirement In The Vegetative Stage?

Your plant in the vegetative stage starts around week four, and that is when you can start feeding them the total recommended dose of potassium. Also, don’t forget to provide your plant with other nutrients such as nitrogen, phosphorus, and others in the NPK fertilizer. Your plant will be taking in a lot as it will have a growth spurt at this stage. Think about a toddler or a teenager who needs to eat a lot to grow and develop. That is why they have intense growth spurts, which you will find with your plant, so you will want to nurture it well.

What About The Potassium Needs Before And During The Flowering Stage?

Your cannabis plant will undergo a pre-flowering time for about one to two weeks before entering its flowering stage. You will know when that time is because your cannabis plant will grow most in the vegetative stage. As a result, they can increase two to three times their current height, and this is when you will want to feed them extra doses of potassium, calcium, and nitrogen.

When your plant enters the flowering stage, it will stop growing. That is how you will know it is in this stage, and you will need to provide it with extra potassium while increasing phosphorous and decreasing nitrogen. That is because, at this stage, the focus will be on bud production, and the excess potassium and phosphorous will help with its development.

Recent Advancements in Potassium Fertilization

  • Optimal Concentrations: The optimal concentrations for nitrogen (N) and phosphorus (P) are approximately 194 mg L–1 and 59 mg L–1, respectively. Interestingly, inflorescence yield did not respond to potassium within the tested range of 60–340 mg L–1, suggesting that the higher levels often used might be unnecessary.
  • Genotype-Specific Responses: Cannabis responses to potassium may vary significantly depending on the plant’s genotype and phenological stage. Different strains can show diverse growth patterns and nutrient needs.


When you decide to grow weed, you will know what nutrients the cannabis plant requires and the environment that will best support its development. That is why it is essential that you learn about the nutrients the plant will need and how much of it to give during certain stages of its growth and development. The focus of this article is on potassium, as potassium is an essential mineral for all living beings. However, your cannabis plant will not require potassium in the early stages of growth until it hits a certain point in the vegetative stage. Then it will need more of it during the flowering stage, and if you feed it well, it will bring you lots of satisfaction!