Potassium Deficiency in Cannabis: Signs, Symptoms and Solution

“Bhrian’s cannabis plants showed brownish leaves, with weakened stems, and poor bud formation in the first production cycle. He decided to top up the soil nutrients with a balanced fertilizer mix before resuming production. It’s his second growing cycle and, despite the added nutrients, his Pineapple feminized cannabis buds are still not well formed. What’s more, they are not giving off the characteristic fruity smell typical of the strain and Bhrian is already stumped for options.”

The scenario described above shows signs that are typical of potassium deficiency in plants. Potassium is one of the primary nutrients required in any plant cultivation procedure. Along with nitrogen and phosphorus, your crops need reasonable amounts of potassium in the soil to develop properly and give the expected yield. Potassium deficiency in marijuana can lead to poor bud development and loss of the aromatic properties of the bud, as described above.

Join us in today’s blog, as we dive into the roles of potassium in plant development, as well as the signs to watch out for in cases of nutrient deficiency. Do your cannabis plants exhibit signs of potassium deficiency? Hang on for tips to correct them in your cannabis cultivation.

Close-up photograph of a blue-and-green petaled cannabis flower.
Potassium deficiency might be the reason your cannabis buds are taking so long.
Source: Esteban López unsplash

Potassium and Cannabis Growth

Have you ever gone on a diet regime, or started going to the gym to lose—or gain—weight? If yes, you might have some insight into specific macronutrients and micronutrients that are important for humans. Along the line, your dietician or gym instructor must have mentioned that potassium is essential for maintaining body water levels and blood pressure. In the same vein, potassium helps drive fluid containing water and other nutrients through your cannabis plants.

So just as carbohydrates, proteins, and fats are classified as macronutrients for humans, potassium, nitrogen, and phosphorus are the macronutrients for plants. Cannabis plants need these nutrients in large quantities to perform their metabolic processes effectively. In cases of nutrient deficiencies, you see the cannabis plants exhibit stunted growth amongst other signs.

But how exactly does potassium contribute to the growth of marijuana plants? We have already stated that it is essential for the movement of fluid within the plants, but there is more that potassium offers your precious cannabis plants.

  • Root development: Potassium ensures that the cannabis plant roots develop appropriately and spread out to take up nutrients from the soil. The root development occurs during the vegetative weeks, so you must ensure that your garden soil has enough potassium from the start of the production cycle.
  • Shoot development: As we stated earlier, potassium is the nutrient that coordinates nutrient transport from the root through the shoot to the leaves. The fluid within the plant vessels gives the shoot strength to support the plant’s leaves and branches. Consequently, potassium plays a role in thickening the plant’s shoot, ensuring that it remains strong enough to support the entire plant.
  • Flower/bud development: The aroma and size of your cannabis buds are one of the major selling points for any cannabis cultivator. Potassium aids proper flower/bud growth, contributing to the size and flavor of your cannabis products by enhancing terpene and oil production during the flowering stage. For example, Blue Mango cannabis buds give off their sweet blueberry scent when potassium is in adequate proportions.
  • Carbohydrate and Protein Synthesis: Potassium is one of the essential nutrients that activate several cellular enzymes that coordinate sugar and protein synthesis in plants. Proteins aid cellular division, which promotes the plant’s overall growth, while sugars improve terpene and essential oil production.
  • Stress resistance: Cannabis plants need some level of stress resistance to survive in the environment. Liberal amounts of potassium in the soil confer some resistance to pests, diseases, and even environmental stress like temperature fluctuations.

Signs of Cannabis Potassium Deficiency

Now that you know the roles of potassium in plants, let’s go over how to recognize the several signs of cannabis potassium deficiency.

Potassium deficiency in cannabis plants shows obvious signs in the leaves, flowers, and shoots, as the root signs won’t be noticed easily. In the leaves:

  • There is some leaf curling, first at the leaf tips before it progresses to the leaf margins.
  • The curled leaf edges then start changing color. Green leaves turn yellow, then brown spots begin to appear, and the leaves eventually die off.
  • For most leaves, the leaf veins are still green even while the margins turn yellow and become necrotic spots.
  • Older leaves (leaves on the lower aspects of the plant) are usually first affected before the deficiency spreads to younger leaves at the top of the plant.

The shoot symptoms of potassium deficiency in plants are most obvious in their vegetative stage, as they lose their structural integrity and become weak and easily bendable. The result is that they can no longer bear the weight of the plant, and this is a pretty advanced sign of cannabis potassium deficiency.

Since potassium plays a vital role in bud formation and development during the flowering phase, potassium deficiency in mature cannabis plants is exhibited in the small buds produced. The buds also don’t give off the usual smell that is typical of the strain you grow, and they take quite more time to form than the usual buds.

Of all the signs, the yellow leaves are the first signs to appear, and you’re more likely to detect them before any other symptom. However, the leaf symptoms of cannabis potassium deficiency overlap with some other cannabis nutrient deficiencies, and it could be quite a hassle trying to detect which of them is affecting the plants.

Here are other conditions commonly mistaken for potassium deficiency in plants:

  • Nutrient burn: This is a condition where the cannabis plant is ‘overfed’ and the excess nutrients are causing the affected leaf to curl up and ‘burn.’ Its symptoms are similar to those of cannabis potassium deficiency but differ in that nutrient burn mostly affects the tips of the plant leaves. It causes yellowing and browning of leaves but doesn’t spread to the leaf margins.
  • Light burn: This occurs when the plants are too close to the light source, causing the leaves to bleach and start yellowing due to the high light intensity. The key difference between light burns and cannabis potassium deficiency is that light burns affect only the plant’s upper leaves, while potassium deficiency progresses from the lower leaves to the top.
  • Nutrient lock: Nutrient occurs when the plants have an issue with taking up nutrients from the soil. The symptoms are most similar to potassium deficiency in plants, but nutrient lock causes generalized stunted growth, with all the leaves affected.
Cannabis leaves showing signs of light burns.
Light burns could appear like potassium deficiency in cannabis plants. Check what light burn signs here.
Source: Roberto Valdivia unsplash

Causes of Cannabis Potassium Deficiency

Several factors could result in potassium deficiency in your cannabis plants, and you should note them if you ever have to deal with cannabis potassium deficiency.

  • Insufficient potassium: Of course, you might be dealing with low potassium levels in the soil. This can be verified through soil analysis, after which you can start to correct it. However, most soil types are rich in potassium, and only extremely leached soils lack adequate levels of potassium.
  • pH range: Cannabis plant nutrient absorption rates are highest when the pH is between 6.0 and 7.0. Fluctuations in the pH values of the growth medium could affect the uptake of several nutrients, including potassium, and impair optimal growth.
  • Over-watering: Too much water in the soil, or increasing the frequency of watering can lead to leaching. When soil is leached, the nutrients have been washed far below the reach of the plant roots, leading to starvation in the plants and stunted growth.

Elevated amounts of other plant nutrients like calcium, sodium, and magnesium could also lead to competition with potassium. This results in reduced potassium absorption and thus, potassium deficiency.

This is especially common with newbie cannabis cultivators who use high-grade fertilizers on their culture medium. This could elevate the nutrients present, causing competition and resulting in the unavailability of one or more nutrients to the plant.

Solutions for Potassium Deficiency in Cannabis Plants

The first step to take when you suspect a potassium deficiency problem in your cannabis seed leaves is to differentiate it from nutrient burns and light burns. Since they both have similar signs to potassium deficiency in cannabis, you must ensure you know what you’re dealing with before you start with any corrective measures.

When you’ve confirmed potassium deficiency, you can carry out the following steps:

  • Request soil analysis reports at a soil science lab, checking for the nutrient profile for which ones are missing.
  • Give potassium-rich fertilizers: Based on the lab results, you can start giving potassium-rich fertilizers in cases of outright lack of potassium in the soil. Potassium sulfate and potassium nitrate are good inorganic sources of potassium, while organic cultivators can get wood ash, tomato feed, or develop compost to supplement their garden culture with potassium.
  • Adjust pH range: We have already stated that the optimal pH values for growth and nutrient uptake for cannabis plants fall between 6.0 and 7.0. Hence, maintaining that pH range in your cannabis farm is essential to promoting adequate nutrient levels for the plants.
  • Monitoring pH is also essential for your cannabis plants when you’ve just applied fertilizer, especially in cases of deficiency. You don’t want the fertilizer–organic or inorganic–to alter the soil pH and negatively impact your plants’ nutrient uptake. You can switch to pH-balanced water to keep the pH in normal range.
  • Maintaining a healthy rhizosphere: The soil-root microbial environment can also contribute to the uptake of plant nutrients. When beneficial microorganisms are present in the soil, their activity helps to ‘unlock’ nutrients like potassium, making them available to the plants.
 A cannabis bud giving off its characteristic scent after harvest.
When the smell hits the air, you just know harvest is near!
Source: Elsa Olofsson unsplash


And that’s all there is to know about potassium and how to tackle potassium deficiency in plants, specifically, your cannabis plants. The potassium element is an essential plant macronutrient; in fact, it is as essential for your cannabis plants as proteins are for you.

Also, in case you’ve got a cannabis potassium deficiency situation on your hands, this guide puts you through the steps to follow to get it corrected. At any rate, you have to ensure that your garden soil for the cultivation process is rich in potassium to get the highest quality yield out of your cannabis plants.

Of course, everyone knows getting the best possible yield starts with getting the best possible inputs. That’s why Growers Choice provides only the best stock of feminized and auto-flowering seeds for your cannabis farm. Need our high-yield Banana OG Feminized cannabis seeds or the newly stocked Purple Lemonade autoflowering seeds?

Check our online stores here and place your orders for your high-quality feminized seeds today!


  • Why is potassium important for cannabis plants?

Potassium is directly responsible for the movement of fluid through the plants’ vessels, supplying the leaves with nutrients from the roots and maintaining the pressure in the shoot. The element is also involved in terpene and oil production that contribute to the development of the buds and flowers and ensure they develop the characteristic aroma for their strains.

  • How do you identify a marijuana potassium deficiency?

Potassium deficiency in marijuana plants is often mistaken for other conditions like nutrient burns, light burns, and nutrient lock. The most outstanding sign of marijuana potassium deficiency is the yellowing and browning of the leaf tips and margins, while the veins on the leaf remain green.

  • What are the signs of potassium deficiency in a marijuana plant?

The signs of marijuana potassium deficiency are usually most apparent on the leaves. The lower leaves start yellowing at the tips, then at the margins, before turning brown. The shoots of younger plants also lose their turgor and become weak and easily bendable. The flowers are also smaller than usual, and they don’t have the typical aroma associated with their strain.

  • How to fix potassium deficiency in marijuana plants?

The first step in fixing potassium deficiency in marijuana plants–and any deficiency–is to check the soil profile at a soil science lab. This helps distinguish between an actual deficiency and a case of nutrients that are unavailable to the plants.

Treatment options include:

  • Give potassium-rich fertilizers. Inorganic sources include potassium sulfate and potassium nitrate, while organic options include wood ash, tomato feed, and compost.
  • Adjust the soil pH to allow the plants access to the ‘locked’ potassium nutrients.
  • You can also boost the microbes in the rhizosphere so that they will free potassium in the soil for plant uptake.

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