Sales Hotline +1 (855) 904-4090
potassium deficiency weed

Solving the problem of potassium deficiency on weed plants


Potassium deficiency in weed can manifest in a number of ways, in this article, we will run down all the potential causes, symptoms and solutions to make cannabis potassium deficiency a thing of the past!


Like every living organism, your cannabis needs specific conditions to survive. You also need to take excellent care of your weed for it to thrive and produce big buds.


Potassium is one of the essential nutrients your cannabis requires to aid growth and morphology in every stage of life. The nute also plays a critical role in defending and responding to stresses and pests.


In the case of a potassium deficiency on weed, your crop is at risk of a potentially deadly threat. You need to be prepared in case the issue arises and combat the problem fast.


Not sure what to look out for or what to do if you notice symptoms? Don’t worry.


Below we answer the most common marijuana potassium deficiency FAQs to help you keep your plants in excellent health and for you to enjoy a massive yield at the end.


We’ll tell you how to spot the problem and how to fix a potassium deficiency in plants and soil.


Let’s get started!


What does potassium do for cannabis plants?

Potassium is crucial for many crucial factors in cannabis. It plays a big part in the photosynthesis process, which gives your weed its bright green color and is vital to health and development. If there’s a drought, the potassium in cannabis helps your cannabis plant resist.


Alongside phosphorus, this mineral aids in strengthening your root system and plant tissue, helping to protect your marijuana from cold, harsh weather.


Considering the number of ways this nutrient is essential to your plants, it’s easy to see how a potassium deficiency in cannabis can significantly affect its lifespan.


A few factors can cause a potassium deficiency in weed, including:


  • Stress
  • pH variation
  • Excess salts
  • Light burn


You’re most likely to see a potassium deficiency during the flowering stage, making your buds lack flavor and smell.


If you want to reap the rewards with massive buds, keep on top of maintenance and look out for any signs and symptoms.


General NPK deficiency information

Potassium is the letter K in the acronym NPK that you often see on organic fertilizer bottles. You’ll notice that for each stage of growth, there are different potassium levels.


NPK stands for:


  • N – Nitrogen
  • P – Phosphorus
  • K – Potassium


At any stage of your plant’s life, you might notice a nitrogen, phosphorous, or potassium deficiency in marijuana.


A nutrient lockout and nutrient deficiency affect your weed in similar ways, but don’t get them confused. The former means you’ve been giving your marijuana too many nutes.


Ensure you understand the difference and how to tackle each issue as it arises; otherwise, you might be putting your cannabis plant in jeopardy when you could be saving it.


Symptoms of potassium deficiency in cannabis

Occasionally, growers might confuse a lack of potassium with other issues like a magnesium, zinc, or phosphorus deficiency in cannabis, at least in the early stages.


Potassium deficiency during flowering


Knowing what to look out for is crucial to get the diagnosis right. The following are common symptoms of a cannabis potassium deficiency.


  • Stunted growth
  • Small leaves
  • Leaves with yellow or white spots
  • Tips of leaves turning yellow, brown, or black
  • Weak and brittle stems
  • Increased space between branches
  • It looks like nutrient burn
  • Leaves curling under


Let’s take a closer look at some of the more common symptoms.

Slow growth

Your suspicions might arise when you spot some plants growing faster than others, also known as stretching. Although it might seem like a great sign, it’s weakening your stems, and your weed isn’t growing as it should. At other times, you’ll see your plant’s growth slow down or stop altogether.


Small leaves

Check for small leaves, which are another pointer to stunted growth. At this stage, the K deficiency in your cannabis is spreading fast and will soon reach the larger leaves. Act quickly in this situation.


Yellow or brown leaves

This symptom is the most common and one of the first to appear. If you notice yellowing or browning of leaves, especially on the tips or edges, you’re likely looking at a potassium deficiency in weed.


Burnt tips

After leaves turn yellow or brown, you’ll see them curling up and looking burnt, similar to an iron deficiency. This is a telltale sign of your plant lacking potassium.


Could your problem actually be light burn?

When you keep your marijuana too close to grow lights, it can get what we call ‘light burn,’ which closely resembles a cannabis potassium deficiency.


Cannabis yellowing leaves


To avoid confusion and light burn, ensure your lamps are the correct distance from your plants. LEDs need to be about 8-18 inches away, and HPS/CMH/MH, between 12-24 inches. If you’re short on space, look for quality cannabis seeds that won’t outstretch your grow room.


How to fix potassium deficiency in soil

Once you identify your marijuana potassium deficiency, you need to know how to fix it. If soil is your growing medium, use the following techniques to combat the problem.


Adjust the pH range

Changes in your pH levels are often what causes a deficiency. Throughout your plant’s life, you need to maintain a healthy pH. The value needs to be neutral and stay between 6.0-7.0 to take in the optimum amount of potassium. You can check levels with litmus paper or a pH kit.


Use good quality nutrients

You are what you eat, and the same goes for your cannabis plants. Use a quality fertilizer rich in essential nutrients, and your seeds and weed will thrive.


If you’ve been making your plant food, it might be time to invest in a high-quality product. Opt for a supplement rich in nitrogen, phosphorus, and potassium. Your marijuana will need different nutes at various stages, so do your research first or ask a professional at your local gardening store.


Flush your plants

When faced with a K deficiency in cannabis, you need to flush your medium. Ensure you use neutral pH water to eliminate any excess nutrients in the soil like you would to prevent a nute lockout. Only use half of your usual fertilizer solution in the water.


Monitor leaves

After you’ve implemented the previous techniques, you’ll need to keep an eye out for new leaves and see how they grow.


Cannabis potassium deficiency leaves


You’ll soon be able to tell if the problem persists or if you defeated the potassium deficiency in your cannabis.


How to fix potassium deficiency in hydroponics

You know how to fix a potassium deficiency in the soil, but what about hydroponics? The methods are very similar, but there are a few factors you need to adjust accordingly.


Amend pH levels of water

You need to adjust pH levels to 5.5-6.5, which is slightly more acidic than soil. Again, test the water to ensure the values are correct and perform a flush to get rid of old nutrients making way for the new.


Use the best hydroponic nutrients

The quickest and safest way to fix your problem is to buy a premade fertilizer. You can purchase one online, and it’ll easily give your plant the nutrients it’s been lacking.


Note that your plant will absorb an organic fertilizer slowly, whereas a chemical or mineral version will go straight to the roots. Make sure a chemical product is suitable for edible plants.


Use seaweed or other natural potassium sources

Homemade fertilizer is an option many growers like to try. Not only does it help resolve a potassium deficiency in weed, but it can also help to fatten your buds during flowering.


When you grow your weed plants in soil, they soak up many nutes from the earth, but when hydroponics is your medium, it’s a good idea to give them a helping hand.


Some of the best natural potassium sources are:


  • Seaweed – mix this plant into the rest of your fertilizer. By itself, it can turn into a slimy mess.
  • Banana peel – soak your skins in water for a few days, and the nutrients will infuse the liquid so you can pour over your cannabis.
  • Wood ashes – sprinkle ash during the first few weeks of flowering, but be careful not to add too much, or you could burn roots and modify pH levels.
  • Bone meal – in addition to potassium, this natural fertilizer boosts your plant with phosphorus, potassium, calcium, and magnesium.


You can use organic plant food to combat a phosphorus or nitrogen deficiency in cannabis, too. Be aware that the sources you use will be different, so be sure to read up on other nutes to know how to notice if your weed lacks them.


Preventing potassium toxicity

We’ve discussed combatting a K deficiency, but what about potassium toxicity in cannabis? You can have too many nutrients in your weed. To avoid this situation:


  • Ensure you flush your plants for a few feedings to clean the root structure.
  • Use balanced nutrients at the correct ratio in the different stages of growth.


Say goodbye to your potassium deficiency in cannabis

You should know more about a cannabis potassium deficiency by now. The next time your leaves or plant are lacking in K or any other nutrient, you’ll spot it and act fast.


Marijuana flowering


The more cannabis you cultivate, the better you’ll get at noticing minor differences with your weed. Luckily, cannabis deficiencies are reversible and easy to fix if you know how to fix a potassium deficiency in your plants.


Good luck with your new cannabis seeds, and keep them healthy. Let us know if you’ve faced a marijuana potassium deficiency in the past and what worked for you.