Do you Have Iron Deficiency in your Cannabis Plants?

An iron deficiency with your cannabis plants is spotted quickly on new leaf growth.

Look for the yellowing between the veins.

But take a closer look to make sure you lack iron because this chlorosis happens from the opposite of the leaf tip near the base of the leaf.

Eventually, these leaves will turn a bright yellow.

If you’re using soil for a grow medium then make sure you’re not over watering because this could inhibit iron from your plants.

Over watering will then lead to a high PH grow medium of 6.5 or higher.

Iron is essential for plant growth and usually found alongside a zinc and manganese deficiency.

So if you suspect your marijuana plants are deficient there are simple ways to fix it.

Let’s check out the signs and make sure your on the right track,

Signs of Iron Deficiency

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

  • Yellowing outside the veins of the marijuana leaf
  • New Leafs (top part of plant ) affected.
  • Young leaves show yellow from opposite tips of the leaf
  • Slow growth
  • Bigger leaves will start to yellow between the veins of the leaf
  • Leaves will start to show signs of burnt tips
  • Eventually, leaf will fall off
  • Pale green leaf color
  • Veins remain green
  • Thin bud development


Caution: Iron can be confused with magnesium deficiency at times, always remember middle and lower leaves are magnesium. Upper leaves are Iron.

Why is iron important to marijuana?

Marijuana needs iron to produce chlorophyll, iron helps the plant absorb sugar, it is also essential for photosynthesis.

Iron is also used for growth of the plant during vegetative stage with assisting in the uptake of nitrogen to the plant.


When you have a deficiency of iron other nutrients can stop the uptake of iron.

If in high amounts such as calcium, zinc, manganese, phosphorus, copper. According to Wikipedia.

Iron can also impact the metabolism of the cannabis plant when lacking.

It is also good to make note that an iron deficiency can also be mixed up with manganese, zinc, copper, phosphorus deficiencies.


Yellowing opposite leaf tip

Causes of Iron Deficiency

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

  • Soil does not drain well because of either high clay based or lack of drainage holes in grow pots
  • Over watering, a classic cause of some deficiencies when growing in soil
  • High amounts of phosphorus, some nutrients when blooming can impact iron levels
  • Growing outdoors, lacking iron in the soil.
  • High PH soil above 6.5 (check your soil ph values )

You can also run into Iron Lockout.

Iron Lockout happens when the PH is above a certain level. Causing the medium to become Alkaline for the roots.

Which stop’s the uptake of iron by your cannabis plants.

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

When growing in soil: PH levels of 6.5 or higher

Hydro and Soil Less Mediums: PH levels of 6.5 or higher

How to Fix Iron Deficiency

The best ways to fix iron deficiency with marijuana is:


Let your plants dry out 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 ranges should be in the following markers:

Soil, 6.0 – 6.5 pH range. Hydro or coco coir, 5.5 – 6.2 pH range


Add iron as a supplement to your nutrient feeding schedule.


Supplement with iron chelates, iron oxides, iron sulfates


Avoid nutrients with excessive amount of zinc manganese, copper.


Fix your drainage situation with more holes.


You could use manure(make sure it is really old), of chicken, horse, or cow but only if your growing outdoors


Chelated Iron for marijuana

Here are some of the popular chelated iron supplements for your marijuana plants.

Liquinox 3032 Iron Zinc Chelated Solution is great for giving your marijuana plants a boost in iron and zinc.

Safe for fruit bearing trees and used for vegetables.

If you are lacking iron you’re probably lacking zinc as well.

Liquinox 3032 Iron Zinc is a great combo that may recover your plants back to health in no time.

Combination iron plus essential minerals

Botanicare Cal-Mag Plus combines the essential minerals of calcium and magnesium, with the bonus of iron.

When using this stuff, it’s hard to be lacking iron.

It comes with 2 percent nitrogen, 3.2 percent calcium, 1.2 percent magnesium, and 1 percent iron.

Take note that it will raise nitrogen levels, so manage accordingly.

Signs of excessive amounts of iron

  • Leafs turn brown , with dark spots
  • Blocks the absorption of other nutrients such as phosporus.
  • Grow medium becomes acidic lower than PH 5

How to correct excess iron

It’s hard to get an excessive amount of iron to your plants.

But it it does happen when growing outdoors and supplement with a manure type fertilizer such as chicken or horse and even cow.

When fresh, this shit can quickly take out your plants, they will die.

When growing indoors, you’re less susceptible to have excessive amounts of iron.


Dry your plants out first.


Flush your plants. With just water.

Your plants will usually recover .


Correct Ph of soil


Slowly incorporate iron back into nutrient feeding schedule.

Final Thoughts


Yellowing between the veins

When your cannabis plant is experiencing an iron deficiency make sure to dry out your plants.

This is a must as they are usually just over watered with a high PH.

Checking the soil PH is a great first step to take when noticing yellowing between the veins especially on new leaf development.

Add some extra iron chelate or start using cal-mag plus in your nutrient feeding cycle.

Plants can usually recover in about week.

Have your plants been lacking iron, did you recover?

Let me know in the comments !

Keep Growing my friends.

image credits: Image

6 thoughts on “Do you Have Iron Deficiency in your Cannabis Plants?”

  1. Right here is the right blog for anyone who would like to understand this topic.
    You realize so much its almost tough to argue with you (not that I personally will need to…HaHa).
    You certainly put a fresh spin on a subject that’s been written about for many
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  2. May I simply just say what a relief to discover an individual who truly knows what they are discussing on the net.
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    • Thanks Scott appreciate it. I do try to put out the best info on all aspects of growing cannabis. Thanks again for the support .

  3. I have been supplementing my feeding with Cal Mag Plus and am experiencing an Iron Deficiency.
    Growing approx 1200 hemp plants in Texas in a clay based soil. Pretty sure my roots are getting to damp and not allowing enough oxygen to them to allow for iron uptake. It appears my only choice may be to constantly provide a foliar spray with chelated iron. Any thoughts ?


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