Iron Deficiency In Cannabis Plants

Adam Parsons

Cannabis Journalist & Staff Writer at Zamnesia

Adam Parsons

Last updated: November 14, 2022

There are many things to take into account when it comes to cultivating cannabis. From where to place your plants to providing regular maintenance, it can be an all-encompassing yet hugely rewarding task for any avid grower. However, even with all the best intentions and level of care, some issues can crop up when cultivating cannabis.

One such problem is iron deficiency. As a hugely important factor in how your plants flourish, they need steady cocktails of the proper nutrients to really help them perform. If one of these is out of kilter, the plant can suffer, sometimes irrevocably. But have no fear; we're here to help you! In this article, we'll delve into not only how to treat iron deficiency but also how to recognise the signs and prevent iron deficiency from occurring in the first place.

What causes an iron deficiency in cannabis plants?

So what causes iron deficiency in cannabis plants? Essentially, it boils down to a few factors. The most common issue is the pH level in the soil being too high (above 7.0), giving it an unsuitable alkali base for your plants.

But other elements could be at play. Too much clay in the soil, diseased roots, and even over-watering can cause iron deficiency issues for your plant. With a lack of iron, the enzyme functions of the plant can suffer, significantly affecting its overall health and leading to a whole host of problems which can lead to plants not forming correctly and even chlorosis.

How to recognise iron deficiency

Fortunately, it's relatively easy to recognise the signs of iron deficiency, as your plants will show you some telltale indications that they're in need of help. Arguably the first, easiest, and most telling sign is the condition of the leaves.

Yellowing will begin to appear on the leaves. While this is a symptom of other ailments, it can be taken as the first indication that something isn’t right, and needs investigating. However, iron deficiency will mainly impact the upper parts of the plant, targeting the freshest areas of growth. Whereas another issue, such as magnesium deficiency, will target the lower to middle sections of your plants. So always be sure to conduct a thorough investigation and study every square inch of your plant to ascertain exactly what the problem is.

How to prevent iron deficiency

While recognising the problem is part of the battle, prevention is key and will most definitely save you a lot of hassle in the long run. Prevention is mainly related to the environment, level of care and equipment you use for your plants. Each factor works with the other, and if they're not cohesive, you can certainly anticipate some problems with your plants.

As mentioned, the pH levels in your substrate will play a massive role in how your plant performs. By choosing a suitable soil, your plants will be able to flourish. You can't expect out-of-this-world buds if you skimp out on the substrate. Also, avoiding any stress to the plant, such as drastic changes in temperature, will also prevent any nutrient lockout and will stop your plants from experiencing iron deficiency from the get-go.

Progress of iron deficiency

Iron deficiency isn't necessarily a death sentence for your plants. While it can take over the entire plant, there are numerous steps of progression, separated into three distinct phases. These are defined as early, progressed and late stages.

Green leaves

This is what growers should strive for. There's simply nothing like the rich green colours of leaves. With no yellow areas or discolouration on the leaf, this indicates a faultless plant that is healthy and completely flourishing.

Early-stage iron deficiency

Although in its early stages, it's entirely possible to spot some degradation on the leaves of the plant. Discolouration will begin to appear in the centre of the leaves. This is one good way to spot an iron deficiency, as many other problems begin either at the edges of leaves, or at their bases. Compared to a healthy green, the leaves will start to turn a light green/yellow colour. This is the earliest indication your cannabis plant might be suffering from an iron deficiency.

Progressed-stage iron deficiency

If left untreated, iron deficiency will develop further on the leaves. While the yellow colour will continue up the leaf, the veins will become much more pronounced and darker in colour as they become starved of nutrients. However, action can still be taken to get your plant back on track. But it's truly a case of recognising the signs.

Late-stage iron deficiency

In the late stages of iron deficiency, the entire leaf will be yellow and discoloured. The veins and midrib of the leaf will have also turned black. The plant's overall health can definitely be determined at this stage, as the leaves will also be limp and drooping.

What iron deficiency looks like in cannabis plants

While we can give some examples of what to keep an eye out for when it comes to iron deficiency, it's really best to see for yourself. What follows is a selection of real photos of cannabis plants that have been afflicted by iron deficiency.

How to treat iron deficiency in cannabis plants

If you find your plant has been affected by iron deficiency, don't panic! You'll be pleased to learn that, fortunately, there are plenty of different ways you can act and save your plant.

✅ pH problems

As discussed, this is one of the most common and preventable factors in causing iron deficiency in cannabis plants. If your plant is showing signs of an iron deficiency, start with the soil. Use a pH testing kit to figure out the level. Typically, the soil should be between 6.0 and 7.0. If you discover the pH level is too high, you can move your plant into a more appropriate substrate or flush it with water and rebalance the pH.

pH & NPK Soil Test Kit

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✅ Provide nutrients

Sometimes an iron deficiency can be caused by a lack of iron in the soil or feed. If you’re using a high quality fertiliser, then it’s unlikely that this is the cause. Usually, a lack of iron in the feed will not be the cause of an iron deficiency.

That being said, it’s easy enough to check. Simply read the label on the fertiliser. If it’s a good quality, cannabis specific fertiliser, then it should be packing iron.

✅ Get pruning

If your plant shows signs of an iron deficiency during its vegetative stage, you can potentially prune away some of the discoloured leaves to promote growth. As the yellowing begins at the top of the plant, pruning will encourage newer, healthier leaves to take the place of affected ones.

✅ Unnecessary stress

Another factor that can cause problems is stress on your plant. Completely preventable, this should be the first port of call when setting up your home growing project, but it can occur during the entire process.

Whether inside, outdoors, or in a greenhouse environment, your plant can be subject to stress that can cause nutrient lockout and subsequent iron deficiencies; along with many other types. These stresses can include transplanting your plant, extreme temperatures, too much darkness and generally poor care.

As you can see, the entire process of treating an iron deficiency is holistic and will require checking off each of the treatment methods to ensure that your plant can be nursed back to health.

Don't let an iron deficiency define your plants

Whether you're new to the task of growing cannabis or have plenty of experience under your belt, it's not uncommon to run into problems from time to time, and iron deficiency can be one of those problems.

Fortunately, it's pretty easy to recognise, prevent and treat. All it takes is a keen eye, a little patience and appropriate action. So next time you see a slight yellowing on your prized plants, investigate the problem and get them back on track. Don't let iron deficiency define your cannabis plants!