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Iron deficiency in cannabis plants

iron deficiency cannabis plant
Posted by: Samuel Thomasino Category: Plant Problems Comments: 0

Iron deficiency in cannabis plants

Iron deficiency in cannabis plants

Iron deficiencies are one of the more common nutrient deficiencies in cannabis plants so growers should ensure they have some understanding of why Iron is needed for plant growth and development. Growers should also be aware of the signs and symptoms to keep an eye out for and also how to treat and prevent an Iron deficiency. This article will inform readers of these points, continue reading to delve into Iron deficiency in cannabis plants.

What does an Iron deficiency look like?

One of the first noticeable signs of an Iron deficiency is yellowing leaves, the leaves can be completely yellow or almost white, this is called interveinal chlorosis. The leaves will slowly become brown and dry as the plant cells die. If the plant is treated in good time the yellowing leaves can return to healthy green leaves, unlike the dry brown leaves which are too damaged. Many growers can misdiagnose the nutrient deficiency as either magnesium or calcium deficiency so it’s vital to give the cannabis plant a thorough check to determine whether the issue is an Iron deficiency. An Iron deficiency will mostly affect the top parts of the plant and the newest growth, which is how to identify an Iron deficiency as Magnesium & Nitrogen will typically affect lower parts of the plant.

A grower can use these images below of a cannabis plant being affected by Iron deficiency to help diagnose the issue.

iron deficiency cannabis plant example 1

iron deficiency example 2

Why is Iron needed in cannabis plants?

Iron is a micronutrient that is vital for the growth and development of cannabis plants, it is only required in small amounts but it plays an important role. Iron is needed to intake oxygen (respiration) without oxygen the cannabis plant is unable to produce chlorophyll. Chlorophyll within the plant is what produces the healthy green colour. Iron is also vital for enzyme function in cannabis plants. Iron is also involved in the photosynthesis process and supports the plant to uptake nitrogen during the vegetive stage.

Potential causes of an Iron deficiency

One of the most common causes of Iron deficiency in cannabis plants is the soil PH levels. If the PH level becomes too low or high it can cause nutrient lockout which stops the plant from up taking any nutrients, including Iron. The cannabis plant will then display Iron deficiency symptoms, potentially along with other deficiencies. Another potential cause of an Iron deficiency is environmental stress on the plant, such as under watering and light leaks. Overwatering can also lead to an Iron deficiency due to stress which then can cause a nutrient lockout.

How to treat an iron deficiency

Once an Iron deficiency has been identified it is vital that action is taken immediately to ensure the plants condition does not worsen and potentially perish. The first step would be to check the PH level and adjust accordingly, this can be done by flushing the system through until the PH level is as it should be, usually 6-7 for soil or coco and 5.5-6.5 for hydroponics. If this method is unsuccessful then growers may need to add Iron in the form of a supplement or complete cannabis nutrient mix – but if you are using a high quality cannabis feed then you should not need to do this.

How to prevent an Iron deficiency

If you are not using a high quality complete cannabis food then it can be difficult to prevent an Iron deficiency but there are still preventative measures that can be taken. Growers should ensure they do not over use nutrients as this can cause a lockout which will prevent the plant from up taking any nutrients, some manures can also cause issues for growers. Manure such as chicken manure increases the PH levels which can cause an Iron deficiency in cannabis plants, growers should be mindful when considering using manure or other fertilisers. Growers can also minimise the risks of an Iron deficiency by using a good quality medium and to regularly check over plants to identify any signs of a deficiency early on. Growers can also minimise the risk of iron deficiency by using a complete cannabis nutrients mix, this will ensure the plants receive the correct nutrients at the right measurements. Growers can also prevent an Iron deficiency by ensuring the plants are exposed to as little stress as possible, such as fluctuating temperatures, over or underwatering or light leaks.


Although cannabis plants only require a small amount of Iron to thrive it’s a very important micronutrient for healthy growth and development. Iron deficiency is a common issue for growers but measures can be put it place to minimise the risk of a deficiency. Growers should also be aware of the signs and symptoms to look out for to rectify the deficiency as soon as its been discovered to ensure the cannabis plant recovers.

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