Iron Deficiency In Marijuana Plants

May 7, 2021

Iron may just be a trace nutrient to the marijuana plants but a lack of it can lead to serious problems. In fact, it is one of the most common mineral deficiencies found in growing cannabis.

As a result, the plant becomes weak and malnourished which often leads to stunted growth and susceptibility to diseases. Ultimately, if nothing is done, this condition affects the yield and quality of the buds. Fortunately, there are many things we can do to stop this before it becomes severe.

In this article, we will cover all there is we need to know about this problem including its causes and treatment. But most importantly, we will learn to properly diagnose it so we can immediately fix it. Through this information, we can easily manage the issue before it gets out of hand.

Iron Deficiency in Marijuana Plants

To grow healthy cannabis, it is vital for the plants to get all the nutrients they need at the right amount. In iron deficiency, the plants suffer from a host of problems that could be tricky to identify and treat. Hence, growers must learn how to tell if this condition is affecting their crop.


The biggest challenge with this problem is that it can be tricky to correctly identify. As such, growers commonly confuse a lack of iron to other mineral problems such manganese, zinc, and nitrogen deficiencies. To avoid this mistake, learn the most common symptoms of a plant that craves iron.

Early Signs

Early Signs
Early Signs – Image powered by

The earliest sign of iron deficiency in plants is chlorosis in which the young leaves turn pale yellow but the veins remain green. Left untreated, it later works down and inward to the older leaves.

To differentiate it from other nutrient problems, determine which part of the foliage turns yellow first. Again, a lack of iron first affects the newest and freshest growth which is on the top part of the plant. Whereas other mineral deficiencies target the leaves on the middle part or base of the plant.

Late Signs

Late Signs
Late Signs – Image powered by

As the condition progresses, the pale-yellow color of young leaves will get brighter and spread on the whole leaf. Luckily, iron deficiency spreads very slowly. Hence, there is ample time to make the right diagnosis and provide the remedy.

However, if left to continue, the yellowing will occur in every new leaf which will give the plant no chance to manufacture enough food. Ultimately, the leaves will drop and the plant will stop growing. Expect to see minimal bud sites as well.


To effectively treat the affected plants, we must first learn the root of the problem. By doing so, we not only get ideas on how to solve it, we also learn how to prevent it. Below are some of the most common reasons for iron deficiency in the marijuana crop.

Bad Soil Drainage

Bad Soil Drainage
Bad Soil Drainage – Image powered by

Growers who like to use soil as the grow medium should make sure that it has a good drainage. Otherwise, the water will pool and make the soil compact and choke the roots. This makes it difficult for the plant to absorb iron which is naturally present in soil but only in minute amounts.

Thus, when choosing a soil, it is best to avoid clay-based materials since this tends to hold water. Most growers use a potting mix since it drains well and has high-quality organic elements.

Excess of Other Minerals

Excess of Other Minerals
Excess of Other Minerals – Image powered by

Most of the time, the problem can be due to the excess amount of other nutrients such as manganese, phosphorous, zinc, calcium, or copper. Too much of these minerals can build up and block the uptake of iron in the soil.

Hence, we must find a way to balance the number of nutrients and work hard to maintain it.

Imbalance in the pH Level

Imbalance in the pH Level
Imbalance in the pH Level – Image powered by

A neutral or alkaline pH level is the most common cause of iron deficiency in marijuana plants. Interestingly, this happens when we use too much fertilizers.

To promote the absorption of iron, keep the soil’s pH between 6.5 to 6.7 by using a pH meter. The good news is, most nutrients also become more available for the plants when we maintain this pH value.


Overwatering – Image powered by

Like the effects of poor soil drainage, an overabundance of water limits the root from taking up iron. Therefore, it is best to know the correct watering practice to avoid this problem.

Using Coco Coir

Using Coco Coir
Using Coco Coir – Image powered by

While iron deficiency can occur in all grow medium, it occurs most frequently in coco coir. This is mostly because this medium lacks organic iron and naturally contains a high amount of salt, making iron less available for the roots.


After confirming the problem and finding out what causes it, we can now confidently save the crop. This involves applying the three basic ways that ensure a quick and effective treatment.

Flush and Add Nutrients

Flush and Add Nutrients
Flush and Add Nutrients – Image powered by

Essentially, we want the grow medium to have the right pH that will promote the absorption of iron. In effect, this method provides the fastest recovery to malnourished plants.

To start, we must flush the grow medium using water that has a pH of 6. This cleansing process makes sure that there are no excess minerals that locks out iron.

The next step is to follow it up in the next watering with an all-around nutrient solution designed for marijuana. Furthermore, to avoid the development of another nutrient problem, we must regularly check the pH of the grow medium.

Spray with Iron Chelate

Spray with Iron Chelate
Spray with Iron Chelate – Image powered by

Applying iron chelate on the affected leaves helps them regain chlorophyll so they can turn green again. But this is only a temporary remedy for iron deficiency. As such, it helps only the leaves that are present during the spraying. Thus, we need to repeat the application every time a new growth appears.

Use Soil Additives

There are many products that are excellent sources of iron while also stabilizing the pH level of the soil. Hence, it’s up to the grower to select which one is the most convenient and suitable. But before starting any treatment, it is vital to flush the grow medium first so that it can facilitate iron absorption.

Compost – Image powered by

Adding compost decreases the pH value by 0.1 to 0.2. This helps stabilize the soil while also enriching it with iron. In addition, it also improves the drainage, helping the soil to readily take up trace minerals. To use, apply 3 to 4 inches of compost on the soil and work it up to 6 to 12 inches deep.

Elemental Sulfur
Elemental Sulfur
Elemental Sulfur – Image powered by

It usually takes months to see the positive effects of elemental sulfur but it is worth it. As such, it provides the longest-lasting cure for the problem, lowering the pH and making iron more readily available to the plants.

To get the best results, work the sulfur 6 inches into the soil about a year before planting. This serves as the perfect prevention of iron deficiency in marijuana plants.

Fertilizers – Image powered by

Another way to lower the pH level and make iron more accessible is to use nitrogen fertilizers. The ones that contain ammonium sulfate or urea works wonders in the soil. However, be careful to give only the amount that is recommended for the plant. For the sake of the plants, we want to avoid nutrient excess at all cost.

Give your plants all the nutrients you need from seedling to harvest. Grab our marijuana fertilizer kit today.

Buy Marijuana Fertilizer

Immediate Treatment is Key to Fixing the Problem

As with all other nutrient problems, the only way to save the plant is by acting fast. While iron deficiency tends to occur gradually, it can spread and wreak havoc on the plant’s health. Moreover, a quick recovery is crucial for a perfect harvest.

As growers, our role is to monitor the nutrient status of the crop and make sure that they are in their optimal condition. Thus, having the patience to do this as well as the skills to spot the first sign of trouble can be very useful. Equally important is knowing what to do when such problem arises.

By learning all the information on iron deficiency, we increase our ability to take care of the plants. As a result, our crop flourishes and we have the guarantee of harvesting enjoyable buds.

FAQs About Iron Deficiency in Cannabis Plants

What are some common signs of iron deficiency in marijuana plants?

The most common sign you will notice in your plant is the yellowing of leaves. Eventually, the leaves will drop and the plant will stop growing. You’ll see minimal bud sites as well.

How can you treat iron deficiency in cannabis?

Flushing and adding nutrients, spraying with iron chelate and using soil additives are some ways to treat iron deficiency in marijuana plants.

Practice and learning are all you need to become an expert marijuana grower. Get started with my blog.

Have you experienced iron deficiency in your marijuana plants? Please leave your comments below.

Happy growing!


The founder of I Love Growing Marijuana, Robert Bergman, is a marijuana growing expert that enjoys sharing his knowledge with the world. He combines years of experience, ranging from small-scale grows to massive operations, with a passion for growing. His articles include tutorials on growing... [read more]


Please Post Your Comments & Reviews

Your email address will not be published. Required fields are marked *

  1. By per ,05 Sep 2013
    this was a very nice cite,Ihope it will help me alot, Thanks
  2. By Stop Copper Deficiencies In Marijuana Plants Now! ,24 Jul 2015
    […] Copper toxicity is when the plant has too much copper. This also means it is unable to use iron (Fe). […]
  3. By Symptom Checker – Identify Marijuana Plant Problems ,24 Jul 2015
    […] Iron deficiency […]
  4. By What Do Marijuana Plants Need? ,18 Sep 2015
    […] small amounts, especially when compare to the macronutrients. Micronutrients include zinc, copper, iron, boron, manganese, and molybdenum. A good option is the Marijuana Booster. A great product […]
  5. By Stop Zinc Deficiencies In Marijuana Plants Now! ,23 Oct 2015
    […] deficiencies are similar to manganese and iron deficiencies, accept that they influence new growth, causing them to become motionless. Zinc deficiency happens […]
  6. By Stop Molybdenum Deficiencies In Marijuana Plants Now! ,10 Nov 2015
    […] your plant has too much molybdenum, on the other hand, it could be mistaken for a lack of iron or copper. Not sure if your plants have a molybdenum deficiency? Read the article Nutrient […]
  7. By Stop Phosphorus Deficiencies In Marijuana Plants Now! ,10 Nov 2015
    […] your plant has too much iron (Fe) or zinc (Zn), it will prevent your plant from absorbing phosphorus normally. There could be a […]
  8. By Stop Manganese Deficiencies In Marijuana Plants Now! ,08 Feb 2016
    […] the pH is too high, or your plant has an overabundance of iron, it may start showing evidence that it is lacking […]
  9. By George Graeber ,03 Feb 2017
    EDDHA Iron Chelate versus EDTA Iron chelate.... what is the difference? EDTA Iron fails when the pH exceeds 6.8. EDDHA remains available from a pH of 4.8 to 10.5 EDTA is often found in blends like 20-20-20 and remains availble […]Read More
  10. By Cain ,24 Dec 2017
    Geez that's unreal ! Very impressed, thank you very much for the World Knowledge 😀
  11. By Jared ,06 Aug 2019
    Learnrd a hell of alot about lot about iron deficiency thank u
  12. By Alex ,31 Jul 2020
    I'm trying to obtain a copy of your free download of "Marijuana Grow Bible," but it's not going through.
  13. By johnathan williams ,24 Feb 2021
    Hi my name is johnathan williams and i am having trouble iding the problem i have a female she is big one but but her some of her leaves even thouh they are new growth they are strarting to dry […]Read More
  14. By Kelvin ,03 Mar 2021
    Hi can you spray iron chelate when flowing

World Icon

marijuana seeds worldwide

200 grow guides

500 Helpful Articles

Group Icon

group of growers

35,000+ Daily Visitors

500,000+ Grow Bible readers

Plant Icon

marijuana strains

1500 Strain Reviews

100 Strains For Sale