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Cannabis Iron Deficiency

cannabis iron deficiency

Cannabis iron deficiency can really mess up your harvests. We have talked about a number of cannabis nutrient deficiencies before, however, today we will focus entirely on iron deficiency. Find out about all the different cannabis deficiencies here.

What does iron do for cannabis plants?

Iron is one of the essential nutrients for cannabis plant growth due to its contribution to chlorophyll formation; the green pigment in leaves. Without it, photosynthesis would not occur. The role of chlorophyll in plants is in light and carbon dioxide absorption, necessary in making plant food.

Another benefit of iron in plants is that it aids in nitrogen uptake. Nitrogen stimulates rapid plant growth, leaves explicitly. If your plants lack enough iron, they will not have the necessary energy to make plant food. As a result, cannabis iron deficiency compromises cannabis plant growth and survival. You should find a way to fix the iron deficiency in cannabis plants because it may adversely affect the quality and quantity of buds. Correcting the issue as soon as possible may prevent severe effects that may be irreversible.

How to identify an iron deficiency in cannabis

Common symptoms of iron deficiency


One of the earliest signs of cannabis iron deficiency is that they are entirely yellow when the leaves first grow. Moreover, the bright yellow can sometimes be severe bordering white. If you confirm diagnosis early and begin strategies to treat your plants, you may reverse the damage. Introducing iron into your deficient cannabis plants will cause the leaves to start turning firm yellow to green, starting from the tips inwards. Therefore, even though your plant looks malnourished with completely yellow leaves, you still have a chance to restore health and integrity to your cannabis plants. This transformation of yellow leaves into green is a unique feature of iron-deficient plants. In the case of other nutrient deficiencies, the plants do not turn completely green even if you made an early diagnosis and treatment.


Iron deficiency in cannabis plants can also cause fungal root problems. As the roots continue to rot you will begin to notice browning in the tap roots. Sometimes the root rot is severe forcing growers to cultivate the soil and reduce soil pH to levels that encourage growth of new healthy tap roots.

Abnormal plant growth

Iron is a micronutrient that assists in optimal growth of cannabis plants. Insufficient iron levels can cause  abnormal growth which may present as strong yellowing of young leaves. Stunted growth of cannabis plants due to iron deficiency is the main cause of yield losses.

What causes iron deficiency in cannabis plants?

It is essential to conduct comprehensive research on nutrient deficiencies in cannabis to understand what causes these conditions. Appreciating the cause of iron deficiency can help you know this to avoid them and the best way to manage the cannabis iron deficiency and maximize the success of your cannabis plants. The following are the common causes of iron deficiency in plants:

  • Poor soil drainage

If you grow your cannabis seedlings in a soil medium, you should pay close attention to your drainage system. If water accumulates in the soil, the pool will affect your plant roots’ ability to absorb nutrients. For this reason, your plants may become iron deficient and thus exhibit symptoms of malnourishment.

Iron rich cannabis soil
Good quality potting soil is added to a clay pot with drainage at the bottom so the excess water can get out

Therefore when you are choosing your soil medium, avoid clay-based materials that tend to hold water. You may consider a potting mix that allows for drainage and still offers high-quality organic elements to your plants.

  • Excess of other minerals

It is easy for growers to bombard their cannabis plants with excess minerals, thinking this will promote growth. If you put plenty of other minerals like magnesium, manganese, and zinc in excess, this will create a buildup and make it difficult for your plants to absorb iron. For this reason, find the perfect nutrient balance that will leave plenty of room for iron absorption, thus preventing deficiency.

  •  pH imbalance

Maintaining the correct pH value will promote the availability of various plant nutrients. Using too much fertilizer will create an alkaline pH level that is one of the leading causes of iron deficiency in cannabis plants. Ensure that you have a pH meter that will help you maintain soil pH at 6.5-6.7, best for promoting iron absorption.

How do you solve cannabis iron deficiency?

Most iron deficiency cannabis solutions focus on pH level maintenance. The proper pH level will promote iron uptake in the roots and eliminate malnutrition in cannabis plants. The best ways to solve your iron problem include:

  • Flush your medium

The recovery solution for your iron-deficient cannabis plants is to maintain pH levels that promote iron absorption. In effect, cleansing your grow medium by flushing using pH 6.0 water will eliminate excess minerals that may be preventing optimal iron absorption.

  • Spray with iron chelate

Iron chelate helps restore chlorophyll in leaves by eliminating any yellowing that has occurred. However, it would be best to regularly spray iron chelate on the leaves because this solution is temporary. Therefore ensure you stay any new growths.

  • Soil additives

Find a specific product that will effectively provide these incorrect nutrient amounts preventing iron toxicity cannabis into your medium. The product should also maintain pH levels. However, before choosing a product, ensure you flush your growing medium so that when you add the soil additives, the roots will readily absorb the iron.

  • Compost

This strategy is perfect for growers seeking to decrease pH levels by at least 0.1 to 0.2. Compost assists in stabilizing pH levels, and growers can also reduce deficiency symptoms as it enriches the soil with iron. It would be best to start with a few inches of compost, at least 3 to inches application on the ground so that your soil can slowly make room for more.

  • Correct watering practice

Overwatering can cause an overabundance of water in your growing medium. Consequently, the roots will have problems taking up nutrients like iron causing deficiencies. The best way to keep track of the water you introduce into your soil is to have a watering practice that appreciates your soil type and drainage abilities.

Plant problems with similar symptoms to iron deficiency

Iron deficiency in cannabis symptoms is similar to magnesium deficiency. The only difference is that iron affects newer upper leaves, whereas magnesium deficiency affects older leaves found in the lower parts of the plants

Final word on iron deficiency

Cannabis iron deficiency is a problem that can cause a lot of losses if you do not diagnose and begin treating your plants early. After following the ideal cannabis iron deficiency treatment, you should start to see changes after at least one week. Although some yellowing might persist, especially when the damage was severe, new leaf growths should be green.

To improve your growing ability, we recommend learning more about all the different cannabis deficiencies.

Picture of Ed Rushford

Ed Rushford

Ed Rushford’s impact on cannabis growing is undeniable. Though he tends to focus primarily on 2 areas, plant training techniques and dealing with disease, pests, and other problems, he has offered many insights into how cannabis plants live and grow. That’s not to say that Ed is unfamiliar with the complete life cycle of cannabis, from seed to harvest, but he uses his widespread knowledge to hone in on the minutia and niche areas of growing cannabis. Ed’s goal is to spread knowledge and allow for everyone to become better growers. About this Author

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