Fix a Molybdenum Deficiency in your Cannabis Plants

When you notice pink or reddish, orange color on the leaves of your cannabis plants this can be a sign of a molybdenum deficiency.

Colder weather can contribute to lacking molybdenum.

It usually starts off with yellowing of the older leaves and also yellowing between the veins.

A molybdenum deficiency is very rare and can be confused with a nitrogen deficiency.

If you suspect your lacking molybdenum check out the signs below to find out more.

Signs of a Molybdenum Deficiency

Here is listing of the most common symptoms of molybdenum deficiency in cannabis.

  • Cold weather or temperature can bring it on.
  • Old leaves yellow
  • Possible yellow between the veins
  • Leaf becomes thick and brittle
  • Tips and stems grow twisted
  • Old and new leaves drop off
  • Brown, dark spots
  • Leaf color is pale
  • Reddish pink colored leaf

Why is molybdenum important to cannabis?

The reason why molybdenum is essential to cannabis is that is part of two major enzyme systems that help convert nitrate to ammonium.

This element is used in very small quantities in the plant.

Molybdenum is most active in the roots or seeds of the plant.

Causes of a Molybdenum Deficiency

Here are some of the causes of molybdenum deficiency in cannabis:

  • Cold weather or significant drop in temperature swings can bring on a molybdenum deficiency.
  • Low PH (check your soil PH values )

You can also run into Molybdenum Lockout.

Molybdenum Lockout happens when the PH is below a certain level. Which then causes the growing medium to become acidic for the roots. This stop’s the uptake of molybdenum by your plants.

Here are some PH values to watch for if they are below these values:

When growing in soil: PH levels of 4.0-5.5

Hydro and Soil-less Mediums: PH levels of 4.0-4.9   


How to Fix a Molybdenum Deficiency

The best ways to fix molybdenum deficiency with marijuana is:


Dry out your plants first; when growing in soil.


Flush your plants with PH balanced water.


Adjust the PH level in soil.


Correct the PH level in water/ nutrients.

The optimal values should be in the following ranges:

Soil, 6.0 – 6.5 pH range. Hydro or coco coir, 5.5 – 5.9 pH range


Correct the temperature in the grow room or tent with a heater

Signs of excessive amounts of molybdenum

  • Leafs turn brown , and dark green 
  • Known to cause an iron deficiency

How to fix excessive amounts molybdenum

Having excessive amounts of molybdenum is very rare in marijuana plants. 

If you do have excessive amounts, it can cause a deficiency of copper or iron.

The best way to fix large amounts of molybdenum is to flush your plants out and correct your pH of your growing medium.


Dry your plants out first.


Flush your plants. With just water.

Your plants will usually recover .


Correct Ph of soil

Final thoughts

It’s very rare to have a molybdenum deficiency, but it does happen from time to time.

This can be due to the cold weather such as growing outside, or your grow room loses heat.

Or you have significant temperature swings I caused the cold on your plants to happen.

The best way to correct this issue is to flush your plants and adjust your pH level of the growing medium.

You may need to try an control the heat in the grow room possibly with a heater if 

Have you had any issues with molybdenum?

How did you recover?

Let me know in the comments.

Keep Growing my friend.

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