How to Treat Iron Deficiency in Cannabis

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Cannabis plant iron deficiency
December 10, 2020
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Plants utilize various ways of absorption to uptake iron found within the substrate, through chelating agents or mechanisms. Iron, amongst other metals found within trace elements, has been found to exist as binary and ternary chelates of amino acids, carboxylic acids, and proteins.

Chelates are organic molecules that pick up and hold the metal ions so that they don’t react with oxygen or other ions. Plants are still able to absorb these chelates through their root system, even though chelates hold onto the metal ions. 

What Can Cause an Iron Deficiency in Cannabis?

Iron deficiency marijuana shows signs of being caused by several things, including overwatering, PH imbalance, as well as having toxicity, or deficiency of another trace element.

Coco coir tends to be the substrate that faces the most iron deficiency problems. So if you plan on growing in coco, be sure to have plenty of knowledge on nutrient deficiencies, how to diagnose each one, and have nutrients or amendments on hand to fix your deficiencies! 

Overwatering is almost always the source of iron deficiency. Most growers generally face iron deficiency in soilless, hydroponic, or aeroponic setups such as a coco coir setup. The reason being is that any excess flushing of your grow medium can potentially lock your plant out of access to the important amino acids, carboxylic acids, or proteins that iron binds to, known as chelates. In soilless, hydroponic, or aeroponic make sure to have enough oxygenation in your reservoir or your plants won’t be able to access the nutrients you have in their water effectively or efficiently. So whether you’re soil, soilless, hydroponic, or aeroponic be sure to follow our recommended watering schedule below! 

  • Offer water feeding every 3 to 5 days. Every other water feeding, you add nutrients into your mix or switch it to your compost tea. 
  • Allow your medium to completely dry out, if you’re in soilless, hydroponic, or aeroponic, wait for your PPM numbers to tell you she’s ready for more food. 
  • If your plants leaves are droopy or sad she’s asking for more water or food, in soilless, hydroponic, or aeroponic, this could mean she needs more air. So be sure if you’re using those soilless, hydroponic, or aeroponic setups you’re providing enough air! 

PH imbalances are the second biggest cause of nutrient deficiencies or toxicities within cannabis. If it isn’t overwatering or enough air to the reservoir, it probably is your PH range. PH ranges play vital roles in cannabis growth and development as every range allows more effective access to specific macro or micronutrients. Macro and Micronutrients are the nutrients cannabis plants need in order to grow, develop, and thrive. These elements include nitrogen, phosphorus, potassium, hydrogen, carbon, boron, copper, and many more like iron. If you’re out of specific PH ranges such as higher than 7.0 or lower than 5.6 PH, your plant will start to become locked out of specific nutrients and show symptoms of deficiencies such as an iron deficiency. Be sure to always have PH adjusters and a PH reader on hand! We recommend General Hydroponics or Nectar of the Gods for PH adjusters (you can also use natural acids however working with natural acids can be dangerous), and Blue Labs PH reader or Dr. Meter PH reader for consistent PH testing. 

Nutrient toxicities or deficiencies cannabis is facing besides iron deficiency can cause an iron deficiency. What do we mean? Iron, like many other trace elements, binds to other elements, proteins, or chelates, to be able to be absorbed through the plant’s root system. If your plant is deficient in the carboxylic acids, proteins, or amino acids iron binds to, your plant won’t be able to absorb iron, which means you’ll see an iron deficiency appear.

How To Identify Symptoms of Iron Deficiency in Cannabis?

As with any deficiency, you can tell by looking at the cannabis plant’s leaves. Iron deficiency is going to show up in the form of yellowing or fading leaves, however unlike a magnesium deficiency, iron deficiencies will show up at the start of the leaf growth, or newer growth, instead of showing signs at the leaf tips or edges and moving inwards. Iron deficiency will begin to yellow from the leaf stem outwards towards the leaf tips, leaving the veins still greenish color tones. Many growers mistake iron deficiency for calcium and magnesium deficiencies, however it’s not to be mistaken with magnesium deficient plants. 

Calcium deficient plants will show symptoms with chlorotic spotting and leaf tip burning. Magnesium deficiency will cause the yellow fading from leaf edge to stem inwards, as well as will eventually become necrotic and die off. Iron deficiency however, does not show any signs of chlorosis or leaf tip or edge damage. 

When diagnosing an iron deficiency cannabis shows signs of, always be sure to check your plant top to bottom to make sure the fading is only happening from the stem outwards. If the majority of your leaves or all of the ones affected show this symptom you most likely have an iron-deficient plant. Iron deficiencies in the soil are quite rare, however, do happen, and whether its soil, soilless, hydroponic, or aeroponic setups, overwatering, and PH imbalances are generally the cause. So always check your PH first and give your girls time to dry out (soil) or give them more oxygenation (soilless, hydroponic, or aeroponic) depending on the grow medium you’re in. 

What Does Iron Do For Cannabis Plants?

Iron, unlike other trace elements, is not a mobile nutrient. Mobile nutrients are “nutrients”, or trace elements, that are capable of moving throughout the plant’s transpiration stream, otherwise being mobile. Iron is an immobile nutrient, however, since iron becomes bound to chelates, it becomes mobile through an absorption process that happens in the plant’s root system. Immobile nutrients are “nutrients”, or trace elements, that once they are transported, absorbed, or sprayed onto a leaf (leaf effect zone only), they’re locked into place. This means the plant can no longer move these elements around to other areas of the plant. 

Immobile nutrients will always show signs in the older growth, as the nutrients have been locked in place longer than new growth. Mobile nutrients will generally show symptoms within new leaf growth if your plant doesn’t have access to any of the elements it’s seeking to move to that growth. 

Iron is vital to cannabis growth and development, however, an interesting fact about iron is that it is not part of the chlorophyll. It does contribute to leaf color and respiration though, how cool is that? It’s also vital for enzyme production to happen as it directly interacts in the enzyme creation processes. Enzymes are proteins found all throughout nature that your substrates microbial life use to allow nutrients to become accessible to your plants. Without enzymes, your plants would not be able to access nutrients within your substrate. These microorganisms within your substrate secrete enzymes to help break down the larger molecules much more rapidly and effectively. Without iron, these processes come to a slow down or complete halt, causing your plant to become not only locked out of iron, but she’ll be unable to access many elements which will lead to other forms of deficiencies. 

Iron is also vital to the structure and function of chloroplast. Chloroplasts are organelles that convert light energy into sugars that can be used by plant cells. Organelles are nuclei that store genetic information, mitochondria, and ribosomes. Mitochondria are membrane-bound cell organelles that generate most of the chemical energy required to power the cell’s biochemical reactions. Ribosomes are minute particles consisting of RNA and associated proteins found in larger numbers in the cytoplasm of living cells. 

So we can see how an iron deficiency can affect vital processes within cannabis plants development, as a deficient plant will be unable to produce biochemical energy for the chemical reactions happening within the plant, as well as, the plant will be unable to read important information or genetic coding (RNA for example) that allows the plant to grow and develop healthily. Remember, soil growers rarely face iron deficiencies, as soil tends to have a resourceful amount of iron. However soilless, hydroponic, and aeroponic are known for being more prone to iron deficiency, specifically coco coir mediums. 

How To Treat Iron Deficiency Cannabis Shows Signs of in Soil?

If you’re growing in soil or living soil you should honestly never face an iron deficiency, and if you do most likely it’s from overwatering, PH imbalance or you have another toxicity or deficiency causing an iron deficiency.

Soil or living soils generally have plenty of iron for the entire grow, as iron is a micronutrient, so even though it’s vital to cannabis to thrive, your plant only needs small trace amounts of it. So if you’ve gone through top to bottom on your plant and checked every leaf, see no other symptoms such as chlorotic spots, leaf edge issues, or curling of the leaves, then chances are your yellow fading is magnesium or iron. Now, these two deficiencies look almost identical, the key difference is magnesium starts fading from leaf edges inwards towards the stem, whereas iron deficiencies show symptoms from stem outwards to leaf edges. Iron deficiencies also maintain the greenish tone in the veins of the leaves. So if you have diagnosed an iron deficiency in soil then here is what you do for the following situations!

Be sure to always check your PH first, as PH imbalances are most common for deficiencies or toxicities in cannabis cultivation.

  • Overwatering 
    • Be sure to allow your plant to completely dry if you think it’s overwatering. Allow about 3 to 5 full days for your soil to dry. 
    • Once dry be sure to give an adjusted feeding, PHed in the right range, and allow your girl to dry out in between feedings. 
    • Follow our guide for watering your plants, water every 3 to 5 days and every other watering switch it to nutrients to offer food. Be sure to allow your medium to completely dry out before your next watering or feeding. 
    • Plants will tell you if they want more water, they get droopy or sad, as well as, they will become droopy or sad if you overwater as well.
  • PH Imbalance
    • For soil, iron becomes deficient past 7.0 PH range and under 5.5 PH range.
    • We recommend staying within these PH ranges for your grow
      • 5.6 to 5.8 Seedling to Early Veg
      • 5.9 to 6.1 Mid Veg to Flower Swap
      • 6.1 to 6.3 Flower to Harvest, as close to 6.3 as possible
  • Nutrient deficiency or toxicity in other forms
    • Iron will become deficient if your plant cannot access certain amino acids, proteins or carboxylic acids. 
    • If your plant cannot absorb the chelates, iron bound to your plant will show signs of iron deficiency, generally within the root system first. 
    • Be sure to make a list of every single symptom your plant shows signs of, diagnose the proper deficiency or toxicity, then start treating it. Once your underlying deficiency or toxicity has been treated you should notice any deficiencies that went along with it, and will soon correct themselves as the macro or micronutrients are able to be absorbed. 

How To Treat an Iron Deficiency Cannabis Shows Signs of in Soilless, Hydroponic, or Aeroponic Setups?

If you’re growing in soilless, hydroponic, or aeroponic setups you will most likely face iron deficiencies more often than a soil grower, specifically if you’re growing in coco coir. These grow mediums have higher chances of becoming locked out of PH ranges or flushed too quickly of the accessible iron you may offer. When growing in these mediums be sure to have enough oxygenation, allow your plants enough time to access nutrients before doing reservoir changes, as well as, be sure to have a wide span of knowledge on deficiency or toxicity information and how to diagnose them. With having your roots directly accessing the nutrients, PH changes, or any temperature shifts, you’ll notice toxicity or deficiencies can happen almost overnight with these mediums. Be sure to have quality PH adjusters and a PH meter on hand! 

Just like soil or living soil grow mediums be sure to make a complete list of every symptom your plant shows signs of. If your plant is only showing yellow fading from the leaf stem outwards towards the leaf edge then you have an iron deficiency. If your fading is coming from the leaf edges inwards, then you have a magnesium deficiency and should seek information on that! However, if it’s iron let’s continue!

Be sure to always check your PH first, as PH imbalances are most common for deficiencies or toxicities in cannabis cultivation.

  • Overwatering or suffocation
    • Be sure to always have enough oxygenation within your soilless, hydroponic, or aeroponic setups. You’re directly responsible for providing your plants with breathable oxygen, which macronutrients are found within. Starving your plant of oxygen, or suffocating it, can actually cause your plant to drown or suffocate.
    • Quality air pumps and air stones will make or break your setup! You absolutely want a ton of oxygenation happening, your plant will be happy with a little excess oxygen, however, with lacking oxygen she’s going to be pretty upset. 
    • Keeping your plants in larger recirculating reservoirs will generally offer the most stable and oxygenated water.
    • Plants will tell you if they want more oxygen, they get droopy or sad, this is because they are having a hard time breathing within all the water. 
  • PH Imbalance
    • For soilless, hydroponic, or aeroponic, iron becomes deficient past 7.0 PH range and under 5.5 PH range.
    • We recommend staying within these PH ranges for your grow
      • 5.6 to 5.8 Seedling to Early Veg
      • 5.9 to 6.1 Mid Veg to Flower Swap
      • 6.1 to 6.3 Flower to Harvest, as close to 6.3 as possible
  • Nutrient deficiency or toxicity in other forms
    • Iron will become deficient if your plant cannot access certain amino acids, proteins or carboxylic acids. 
    • If your plant cannot absorb the chelates, iron bound to your plant will show signs of iron deficiency, generally within the root system first. 
    • Be sure to make a list of every single symptom your plant shows signs of, diagnose the proper deficiency or toxicity, then start treating it. Once your underlying deficiency or toxicity has been treated you should notice any deficiencies that went along with it, and will soon correct themselves as the macro or micronutrients are able to be absorbed.
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