Reasoning For Yellowing Leaves During Late Flowering

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    Are Yellowing Leaves During Late Flowering A Problem?

    Cannabis leaves turning yellow during the flowering stage or near harvest is often the most frustrating thing that can happen for cannabis growers. After all, you thought you were doing everything well, and you were in the clear. You’re now ready to start enjoying the efforts of your hard work and patience. However, it’s week nine, flowering starts, and to your horror, you notice that the lower cannabis leaves are yellow. Some of them even look like they will die!

    What did you do wrong! Can this be fixed? Does it even need to be fixed?

    The main reason for yellow leaves, during late flowering, is a nutrient deficiency. (Nitrogen deficiency is the most common reason)

    Find out more in this article where I will tell you the following:

    • Why Nitrogen is Necessary
    • Symptoms of Nitrogen deficiency
    • How to Fix a nutrient deficiency
    • Other Reasons For Yellow Leaves
    • And More . . .

    Why Is The Article Concentrating On Nitrogen Deficiency?

    There are numerous reasons for a marijuana plant leaf turning yellow. However, nitrogen deficiency is the main reason for yellowing leaves appearing during the late flowering state. As a result, this article will go in-depth on the reason and methods to cure nitrogen deficiency in weed plants.

    It Might Not Actually Be A Problem

    Ed Rosenthal, who is a famous horticulturist, and cannabis advocate, remarks that a yellow, lower level, fan leaf might not actually be a problem. In fact, it is likely a good sign when leaves turn yellow during the flowering growth stage. The reason for it being positive is explained below.

    During the final flowering growth stage, it is advisable to add high phosphorus, low nitrogen flowering formula to your plants. A marijuana plant that is given this formula will be lacking nitrogen. This lack of oxygen results in the lower fan leaves, turning yellow and/or brown, wilting, and eventually falling off. What’s positive about this is that, because there is not enough nitrogen, essential plant nutrients will concentrate, where the buds are located on the upper canopy. And the added nutrients, where they are needed most, will likely result in a better cannabis flower.

    Nitrogen Deficiency

    Why Does Cannabis Need Nitrogen?

    Nitrogen (“N”) is an essential plant nutrient as it helps with the following:

    • DNA Production
    • Forms the amino acids that starts the process of building essential proteins
    • Develops chlorophyll

    All of these are essential for an abundant harvest.

    How Can You Tell If you Have a Nitrogen Deficiency?


    A nitrogen-deficient affected plant leaf will turn yellow and/or brownish, become soft, and tend to fold inward. This can look similar to other problems that can cause yellow leaves. The most noticeable difference between a nitrogen deficiency and other nutrient deficiencies is that nitrogen deficient plant leaves (yellow leaves) first show up on the older, lower leaves that are near the plant’s base. (Upper leaves tend to look normal)

    This indicates a nitrogen deficiency because when the older leaves that do not have enough nitrogen sacrifice themselves for the newer or upper leaves. The nitrogen lacking plant is essentially eating itself to get all of its required nutrients.

    How Can I Fix Nitrogen Or Other Nutrient Deficiency?

    To fix it, you simply add organic or synthetic fertilizer to your plants. An all-purpose growing fertilizer should do this for you. However, the results are often not as precise as you might prefer. So, it is best to apply specific nitrogen-based fertilizers. For the organic route, older poultry manure should do the trick

    DO NOT OVER-DO IT-Too much nitrogen leads to toxicity, which can be as big or a problem as a deficiency. Therefore, it should go without saying that you need to follow the instruction for using the fertilizer.

    Final Thoughts

    If you follow proper growing procedures, nitrogen deficiency should not occur. This means prevention should be your number one goal. So, apply a general grow fertilizer and plant food. Also, check your soil ph, don’t over or underwater, etc. Above all, watch your cannabis plants like a hawk to see if any nutrients or other problems. And when, and if a problem occurs, be sure to nip it in the bud before it gets worse.


    Other Reasons for Yellow Leaves

    There are several other reasons for yellowing cannabis leaves, which will be detailed below. Some of the more common reasons are:

    Too High Or Too Low Soil pH (Or other Growing Mediums)

    A too acidic or too alkaline growing medium (soil, water, coco coir, etc.) makes it harder for your marijuana plant to absorb nutrients, which in turn results in a nutrient deficiency. And, nutrient deficiencies (especially not enough nitrogen) are a major reason for yellowing plant leaves.

    How Can You Discover and Fix This?

    Kensizer 3-in-1 Soil Tester, Soil Moisture/Light/pH Meter, Gardening Farm Lawn Test Kit Tool, Digital Plant Probe, Sunlight Tester Water Hydrometer for Indoor Outdoor
    Soil pH Meter

    All you have to do is check the soil or water, if you are growing hydroponically, with a PH pen. This article on PH pens for soil and hydroponics will tell you how you can best do that.

    How To Fix Soil and Water pH Problems

    There are a number of things that you can do to fix incorrect Soil pH Some these ways are listed below:

    • PH Up or PH Down-PH Up and PH Down are commercially manufactured nutrient solutions that are designed to fix any soil pH problems.General Hydroponics pH Control Kit for a Balanced Nutrient Solution


    • Naturally Increasing Soil pH-Specialized grounded agricultural limestone will reduce soil acidity.
    • Naturally Decreasing Soil PH-Sulfur and aluminum sulfate are commonly used to reduce soil pH.

    Not Watering Correctly (Over and Under)


    As many newbies and even experienced growers are often overzealous when it comes to watering their plants overwatering is one of the most common cannabis growing mistakes.

    Root Rot is one of the the worst that can happen when plants are overwatered. Overwatering also leads to your cannabis plants not getting enough oxygen, which can result in malnourished plant roots, which in turn, might result in yellow or yellowing plant leaves.


    An underwatered cannabis plant’s leaves are identified by a leaf drop with the leaf tips turning yellow and wilting.

    Light Deficiency

    Light deficiency is a definite problem; but, it is not likely the reason for yellow cannabis leaves during the late flowering stage. The reason is that lack of light tends to only turn young leaves yellow.

    Iron and Magnesium Nutrient Deficiency

    Iron and magnesium deficient marijuana plant leaves look similar to nitrogen-deficient plants. However, they’re subtle differences.

    Magnesium Nutrient Deficiency

    With a magnesium deficiency, the leaves will be a vivid yellow that has been described as being near white. Additionally, these affected leaves will appear on new growth. A major, noticeable, difference though is that, as time passes, magnesium deficient leaves will turn green.

    Iron Nutrient Deficiency

    Iron deficient plant leaves look similar to magnesium. The big difference is that with an iron deficiency the yellow, affected leaves, first appear on the upper and inner plant leaves.

    Miscellanous Reasons For Yellow or Yellowing Leaf

    There are several other reasons for yellowing leaves (other than a nitrogen deficiency) that are listed below.

    1. Heat Stress or Too Cold
    2. Not Enough Light for seedlings.
    3. Pests-The spider mite, as an example, can cause a yellow leaf to appear.
    4. Bud Rot Fungus

    Click Here for an excellent overview of recognizing and fixing each of the above problems.






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