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This being a common issue for most novice growers, we have created a mini guide on how to identify and treat phosphorous deficiency in cannabis to tackle it.

When plants, such as cannabis do not get the needed minerals for growth, a couple of problems can occur.

Phosphorous is an essential mineral that is needed for plant growth. It is an important element that helps to facilitate cell division and growth of new tissue. It also helps in transporting amino acids throughout the whole plant, and this is just a beginning.

Phosphorous is essential for all the growing stages of cannabis, during the vegetative stage and most important during the flowering stage.

Phosphorous deficiency happens when your plant does not receive the right amount of phosphorous it needs for its growth. Phosphorous deficiency can lead you to harvesting very low yields.

But how do you know if your plant is lacking phosphorous? And do you know how to solve phosphorous deficiency? Here are ways of identifying and treating phosphorous deficiency:

 Symptoms of Phosphorous Deficiency in Cannabis

There are many ways of identifying phosphorous deficiency in cannabis.

  • The lower and older leaves usually end up being affected first, the signs mostly show in leaves that turn dark green or yellow. In other cases, they will turn blue and purple.
  • As phosphorous deficiency continues going on the leaves will dry and thicken and end up becoming stiff. In this process the dark parts of the leaves will develop a shining appearance.
  • In most times, depending on how severe the phosphorous deficiency is, the stems may turn purple or become bright red. This deficiency starts at the lower stems and goes all way up.
  • The slow growth in your cannabis plant also means that it is lacking phosphorous. In most times if this problem is not fixed then you will end up harvesting nothing.
  • The lower leaves in your cannabis plant may also begin to die. You will also notice that the affected leaves will begin curling in shapes different from the others.
  • The weak plants end up being easily affected by diseases and pests.

The Causes of Phosphorous Deficiency

There are many factors that can lead to phosphorous deficiency in your cannabis plant:

  • Over watering the cannabis plant.
  • A high PH level of above 7 and also low PH levels.
  • Using excessive phosphorous.

Different Ways of Treating Phosphorous Deficiency in Cannabis

Here are the different ways of solving phosphorous deficiency in your cannabis plant in order to get good harvest.

1.   Check the pH and adjust to the correct range

Your cannabis plant may be showing signs of phosphorous deficiency because the pH at the plant’s root is in the wrong range. This means that your cannabis plant won't be able to take in phosphorous through its roots because the pH isn't in the correct range. Therefore for optimum growth of your cannabis plant the first essential step is ensuring the pH is the recommended one.

Cannabis properly absorbs phosphorous in soil with the root pH of 6.2-7.0. Then cannabis takes in phosphorus well in hydro at a pH of 5.5-6.2. The most essential thing is to also ensure that the pH is not too high or low.

2.   Ensure you provide the correct nutrition

Most cannabis growers usually have already provided their cannabis plant with the right phosphorous because it is present in good soil and other cannabis friendly substance. But don’t forget that just because you have provided the right amount of phosphorous that you don’t need to give your cannabis plant other essential nutrients.

It is important to use organic fertilizers to grow your cannabis plant. It is a natural way that doesn’t have a lot of complications. You can try adding Bone Meal and Bat Guano and fish meal; they are a major source of phosphorous. Bat Guano is essentially used in all growth stages.

Bone meal helps you when you do not have enough phosphorous, use it by just adding it at the top of your soil. Don’t add too much though. The bone meal helps in growth of the plant and high bud development.

3.   Ensure you provide the correct temperature

A temperature below 60 degrees or 15 degrees and frequent changes in the temperature makes it hard for the cannabis plant to be able to use phosphorous well. Cannabis plants thrive well in a comfortable and cool environment and if the temperatures are very low then the cannabis plant is likely to develop phosphorous deficiency systems. The important thing is to always check the temperature and ensure that it is in the correct range for cannabis growth.

Remember that with the wrong temperatures you won’t be able to harvest a bumper harvest because the cannabis plant will not be able to produce anything. You can always check for cannabis temperature tutorial online in order to make sure the cannabis plant is growing at an optimal temperature.

4.   Make sure to water adequately

A simple thing like proper watering of cannabis can ensure that you prevent phosphorous deficiency. The major mistake that most growers make is overwatering the plant. Instead of watering regularly and in small amounts, it is better to water less often and to therefore ensure that there is saturation of the entire soil contents.

*A tip to remember is to always wait for the soil to dry between watering.

Remember that consistent overwatering cannabis will lead to serious growing problems of the cannabis plant. Proper watering is also a way of taking care of the roots. Roots that have been excessively watered will not get a chance to develop.

5.   Watch out for signs of resurgence

After making sure that you have done all the steps mentioned above, regularly check your cannabis plant to ensure that the cannabis phosphorous deficiency symptoms are starting to disappear.

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New healthy leaves will start developing after a week or some other time. You need to just check out for new leaves because the ones that had been destroyed won’t recover.


Once you follow all the steps, your cannabis should recover after a few weeks or several days. Remember you can’t give a cannabis plant too much phosphorous but remember that too much is not healthy too.

The trick is to identify and treat phosphorous deficiency as soon as it pops up, the signs mentioned above should guide you.

Luis Cordova
Luis Cordova

Luis Cordova is a distinguished author, and renowned expert in cannabis cultivation, who possesses a Master's degree in Plant Biotechnology and Pharmaceutical Science. As a valued contributor to highly esteemed publications such as Cannabis Training University and Maximum Yield Magazine, Luis has emerged as a trusted source of guidance and knowledge in the cannabis industry. Having written thousands of informative articles, Luis is widely recognized for his comprehensive expertise on cultivating cannabis, both indoors and outdoors.

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