Potassium deficiency in marijuana plants

Potassium deficiency in marijuana plants can cause a number of problems. Potassium is helpful in a huge number of your plant’s natural processes.

This is simply because potassium assists with the transport of water, which reaches every part of the plant. Every life stage that your plant goes through will require adequate amounts of potassium, and every new growth will need it too. The buds are no exception.

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Potassium also helps with water respiration, photosynthesis, the strengthening and thickening of stems, and disease resistance. To put it simply, potassium is extremely important for the well-being of your plant. It is, therefore, crucial to ensure that it is receiving enough potassium to thrive.

Signs of a potassium deficiency

If you are growing your marijuana plants in a hydroponic system, you can rest assured that whatever symptoms you are seeing in your plants are not in fact due to a potassium deficiency. Potassium deficiencies almost never happen in plants that are growing in hydroponic systems.

Signs of a potassium deficiency

They do, however, happen in planting mediums and outdoor soil every once in a while. They can even happen if your soil is especially rich in fertilizers and nutrients – and if this is the case, incorrect fertilization is probably the cause.

If your plant is lacking in potassium, it might actually be taller than the plants around it, causing the plant to stretch out and its stem to weaken. This can be deceiving, but you will realize that your plants have a problem because of the tan or brown-colored tips and edges of leaves at the bottom, as well as spots of necrotism and leaf death.

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Left untreated, the leaves will start to show chlorotic spots, and they become patchy with red and yellow bits. The veins of these leaves will remain green, but the petioles and stems will become reddish in color.

Deficiency in marijuana plants

You will also start to notice your plant’s growth slowing down, and new leaves will grow smaller in size. These symptoms occur when the deficiency has become more serious.

Unlike other deficiencies, a lack of potassium is extremely mobile. It will move upward toward the biggest fan leaves, where you will be able to notice necrosis on the margins. These fan leaves will die.

In contrast, if your plant has too much potassium then it will cause the fan leaves to change color in a different way – between the veins they will be yellow or whitish in color.

Not sure if your plants have a potassium deficiency? Read the article Nutrient deficiencies in marijuana plants for a list with pictures of all deficiencies.

It is always best to ensure that no deficiencies will be present in your grow in the first place. By balancing your nutrients using my own recipe of NPK-balanced fertilizers, you will be able to get an amazing grow without deficiency issues!

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Prevent future deficiencies

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How to fix a potassium deficiency

Like with many other nutrient deficiencies, a lack of potassium can be avoided from the get-go by using Marijuana Booster for your plant. Marijuana Booster provides your plant with fertilization as well as a feeding schedule, so it takes out a lot of the difficult planning and decision-making that goes along with giving your plants the proper nutrients.

Fix potassium deficiency in marijuana
Fix potassium deficiency in marijuana

If you do find that your plant has become potassium deficient, you can try using a bloom fertilizer that is water-soluble and has lots of potassium. Another substance that is packed with potassium is wood ash.

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It delivers nutrients to your plants very effectively. If that’s inaccessible to you, you can also try liquefied kelp, potassium sulfate (wiki), potassium bicarbonate, potassium dihydrogen phosphate, or potassium silicate. For a slow-release provider of potassium, try greensand or granite dust.

Also read Identify marijuana plant problems

Sometimes potassium isn’t being taken in correctly due there being too much calcium or nitrogen. You can check your water’s pH and flush out the system, using water with a half-dose of nutrients. You can then wait and see if your plant begins to improve.

List of marijuana plant symptoms

Leaf color:
Brown or burnt leaf edges
Pale colored leaves
Yellowing of the lower, older leaves
Dark, brown spots
Burnt leaf tips
Leaf symptoms:
Death of leaf tips
Spots on leaves
Older leaves falling off
Plant symptoms:
Slowed growth
Twisted and abnormal growth
Curling leaves (under or upward)
Stretching – characterized by large spaces between nodes
Plant is too tall
Buds not getting fatter

Potassium deficiencies often resemble iron deficiencies. The tell-tale way of knowing that a potassium deficiency is a problem is by the curling leaves, the burnt edges, and leaf death.

Starting a new grow and want to make sure no Potassium deficiency will pop up? I have created multiple grow sets which features all you need in order to grow healthy plants from seed to harvest!

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Marijuana grow set

FAQ about potassium deficiency in marijuana plants

Do marijuana plants need potassium?

Yes, your marijuana plants need potassium to survive. It is responsible for healthy growth and reproduction. So if you want higher yield make sure your plants don’t suffer from potassium deficiency.

What are the most common marijuana leaf symptoms of potassium deficiency?

There are many ways to can identify potassium deficiency in your marijuana plants. Here are 3 most common symptoms that you will see on leaves: Death of leaf tips, Spots on leaves, Buds not getting fatter.

How do they fix potassium deficiency in marijuana plants?

In order to fix potassium deficiency in your marijuana plants, you can try bloom fertilizer. It is water-soluble and has lots of potassium. Another substance that has a lot of potassium is wood ash. It delivers nutrients to your plants very effectively.

Thanks for reading. Please leave comments or questions below and don’t forget to download my free grow bible


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Robert Bergman


Robert Bergman is an Amsterdam-based marijuana grow expert who has years of experience from small grows to massive operations ... See profile

13 comments on “Potassium deficiency in marijuana plants”

  1. It’s just hard to tell whether it’s nutrient burn or potassium deficiency because they’re very similar. My tips of the leaves have turned blackish Brown but I’m also getting the the leaf Edge burn in the big fan leaves towards the bottom of the plant and some yellow spotting so it sounds like Nute burn and deficiency of nutrients at the same time

  2. Hi I got 4 plants In not 4th week flower .3 look great as they should but one is very pale * yellow on the serations on the fingers of leaves .they all got exact same conditions help thanks

    • Tim,

      Join us at: support.ilovegrowingmarijuana.com
      There you can add images and get help from our many friendly members and expert support staff. Happy growing 🙂

  3. I’m a first timer, growing 2 plants indoors in soil.
    2 weeks into flowering one of them has a few leaves turning yellow and the other has some leaves with Brown spots. Not sure what to do, any suggestions would be appreciated!

    • Tim, Join our forum at: support.ilovegrowingmarijuana.com We are much better suited to help you learn from there. Thanks 🙂

  4. […] You also might notice areas where growth slows or becomes irregular. Remember that potassium is very important to the transfer of water and other nutrients throughout the plant. This means that if you have a large deficiency, it can affect the health of the whole plant. To treat your potassium deficiencies, try adjusting the fertilizer mix you are using or add a water-soluble potassium additive. Read more about potassium deficiencies in marijuana plants. […]