iron deficiency cannabis

How to Treat Iron Deficiency in Cannabis

Just like any other plant, cannabis plants need special nutrients to grow healthy and to produce good yields. One of these nutrients is iron. This nutrient is needed by cannabis plants for proper growth and overall development. Iron deficiency cannabis symptoms are seen if this element is deficient in your plant’s diet.

Iron deficiency is not a very common issue and can be easily misdiagnosed even by professional or expert growers. This is a guide to help you identify an iron deficiency in cannabis plants and how to treat this kind of nutrient problem as well.

How to tell if your cannabis plants have an iron deficiency?

The very first thing you’ll notice in cannabis iron deficiency is bright-yellow areas on new leaves. Usually, iron deficiency may happen together with other nutrient deficiencies and nutritional problems.

There are several causes of iron deficiency in cannabis. The most common one is the root and soil pH problems as changes in pH can lead to poor absorption of nutrients. Also, cannabis plants suffering from stress may exhibit nutrient deficiencies and one of these is iron deficiency. Stress in cannabis plants can come from different factors in their environment.

Cannabis plants may become stressed when temperature and humidity problems are not fixed. Also, overwatering and under – watering may also lead to stress and eventually, nutrient problems. Plant training may also cause stress. These are special training methods that help improve yields and control the size of indoor-growing cannabis plants.

Most of the time, nutrient deficiencies like iron deficiency may clear up as soon as the plant recovers from stress. 

The following are the most common symptoms of iron deficiency in cannabis plants

  • New leaves turn yellow as soon as they sprout from the branches/stems.
  • The leaves may be yellow to bright yellow, sometimes, the color may already be white.
  • Badly damaged yellow leaves will never recover even if you have managed to solve iron deficiency problems. Sometimes the yellow areas on the leaf turn green which means that the plant is starting to recover. This may begin from the tips and will move to the base of the leaf.
  • A yellow leaf can completely become green and will look healthy again despite starting as yellow due to iron deficiency. This ability of young yellow leaves to turn green is common in iron deficiency, unlike other deficiencies when leaves cannot recover or return to their previous healthy state.

Iron deficiency may also appear like other nutrient problems like magnesium deficiency. The difference is iron deficiencies affect the newer or the upper leaves while the other affects older and lower leaves.

How to treat iron deficiency cannabis?

The following are effective ways to deal with cannabis iron deficiency.

1) Prevent plant stress

Stress is the most common factor that triggers nutrient deficiencies. When plants are stressed, these may not absorb nutrients properly leading to iron and other nutrient problems. Control stress right away.  Make sure that lighting inside the growing area is adequate and you’re watering your plants correctly. Check humidity and temperature and correct any problems ASAP. Incorrect cannabis plant food can also lead to stress and nutrient deficiencies. If you have just recently changed your formula and soon after noticed changes in your plants’ leaves, discontinue the new food and flush your system with clean, pH-balanced water. Change your formula to a better one.

2) Correct pH

Check soil and root pH through the water runoff coming from the holes of your pots or containers. Usually, iron deficiency happens when the root pH is high as this element is locked in the roots. pH above 7.0 is common in soil and also in coco coir. Hydroponic setups are usually lower than 7.0

If you think that your plants are suffering from iron deficiency because of high pH, discontinue any plant food or fertilizer and water your plants with clean, pH-balanced water. Doing so will remove any salts which may be causing poor iron uptake.

Remember, iron is best absorbed when the roots are 6.0 to 6.5 pH range. When growing in hydro or coco coir, pH must be kept at 5.5 to 6.5 pH.

3) Feed correct nutrients

You don’t need to add iron if you suspect an iron deficiency. Usually, iron is very abundant in soil and in water and is simply locked in the roots or in soil. Also, some nutrients may affect the way iron is absorbed. Calcium, magnesium, and copper toxicity can lead to iron absorption problems in cannabis.

If you think that your plants are suffering from iron deficiency despite having correct pH, you must flush your system with clean, pH-balanced water and afterward, add a plant food supplement that contains Magnesium, Calcium, and Iron.

4) Always take care of your plants’ roots

Your plants eat and drink through the roots and thus, it’s very crucial that you keep your roots healthy. Usually, iron deficiencies show when your plants have root problems or when it is overwatered. Observe proper watering schedules and avoid watering when the soil is moist or wet but only when it’s dry and high. Avoid underwatering and overwatering as these can also lead to plant stress.

Some tips to avoid iron deficiency in cannabis

Avoid cannabis iron deficiency by using only commercially-prepared nutrients. Usually, homemade fertilizer and compost may not be correctly formulated, and thus feeding these to cannabis plants can lead to different nutrient deficiencies.

Always keep the correct temperature and humidity levels in your growing area. Keep a watering schedule; water only when the soil is dry and never when it’s wet or moist to avoid overwatering and stress.

Get other expert tips on how to cultivate weed from this best selling marijuana grow book!


An iron deficiency cannabis problem is not too common and is preventable. If you spot leaf changes and growth problems in your plants, don’t immediately suspect iron deficiency as iron problems occur together with other nutrient problems. Consider plant first aid: flush your system with clean and pH-balanced water. Finally, control stress as stress can indirectly lead to different problems and conditions in cannabis plants.

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