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How To Recognize Iron Deficiencies On Marijuana Plants


iron deficiency marijuana plant

Iron deficiencies can occur on occasion in planting mediums, hydroponic systems, and in outdoor marijuana plants. In the event of an iron deficiency, you will notice a lack of chlorophyll in the new leaves, but they will not contain necrotic spots. These leaves will turn bright yellow with green veins. Newer leaves will exhibit “chlorotic molting” which produces brown marks on the leaf center.

Iron deficiencies are similar to magnesium deficiencies except that iron affects all new growth except the lower leaves. Magnesium attacks the lower and middle leaves at the start. Iron does not move fast around the marijuana plant, giving it a low mobility.

Iron is vital particularly for younger, still growing tissues in the marijuana plant. Enzymes require iron to function properly, and iron also allows for the synthesis of chlorophyll.

Solving this issue isn’t easy, but the right fertilizer and water balance can help. Using a product like Marijuana Booster is probably the ideal choice of many growers, but there are also other options at your disposal. For instance, you can opt for a foliar feeding option with a chelated iron fertilizer that also contains zinc and manganese (iron, zinc, and manganese deficiencies often occur in conjunction. Other fast-acting options include:

  • Iron chelates
  • Iron oxides (Fe2O3 or FeO)
  • Iron sulfate (FeSO4)

These should be added filially and directly to the planting medium itself. Rusty water may also be a solution.

An Fe deficiency may indicate a pH imbalance. Foliar feed with Fe chelated fertilizer containing Fe, Zn, and Mn, since these deficiencies are often found in combination. Other Fe-bearing supplements include compost, Fe chelates (often found in hydroponic micronutrient supplements), iron oxides (Fe2O3, FeO), and iron sulfate (FeSO4) for fast absorption. Supplements should be added both filially and to the planting medium. Adding rusty water also works. For more information about nutrients check marijuanabooster.com.

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About Author

Robert Bergman is a master marijuana grower. Robert Bergman is the author of 'Marijuana Plant Care' and 'The Marijuana Grow Bible'.


  1. About three inches from the stem, and try to find one that has already started to rust, just to be sure it’s the right kind.

  2. We see this more often in house plants or outdoor potted plants, and usually just stick a rusty nail in the soil next to the plants.

  3. Great article! In my experience, iron deficiencies are pretty rare, but they do crop up if the pH is off or when using ultra-filtered water like RO (Reverse Osmosis Water). Sometimes I’ve seen an iron deficiency when someone goes crazy with the nutes, for example once I saw a person get an acute iron deficiency the day after she added a bunch of chicken compost on top of her soil. Removing the chicken compost (as best she could) and giving the plants a good flush seemed to clear up the iron deficiency problem pretty quickly.

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