Magnesium Deficiency In Marijuana Plants

The purpose of magnesium is to encourage strong, healthy veins and stimulus on the creation of marijuana leaves. It also plays a role in producing chlorophyll and breaking down enzymes.

Magnesium deficiency can happen in any plant medium and hydroponic system. But this rarely occurs when growing marijuana outdoors.

When signs of deficiency occur if must be dealt with quickly or else it will become a major problem causing the plant to quickly lose many of its lower leaves. Magnesium is a nutrient that can move around, so the plant has the ability to move it from the old leaves to new ones.

Your plant will take magnesium from the older leaves and move it to the new leaves. This explains why magnesium deficiency has a tendency to show up towards the bottom of the plant and on the older leaves.

Signs of a magnesium deficiency

Signs of magnesium deficiency weed

Symptoms begin in the lower leaves when they start to turn yellow and show chlorosis. The leaves begin turning inward and will soon die. The outlining of the leaves will feel dry and brittle. The deficiency will move up to the middle and upper half of the leaf, and the growing shoots will start going from pale green to white. All of the petioles and stems will also become purple in color.

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    Sometimes you may notice light brown spotting on the edges if the issue continues to worsen, even though it is possible this could be a little bit of another deficiency that comes along with magnesium deficiency.

    You can easily avoid and solve magnesium deficiencies once you are aware of how to handle it. We will go into more detail about this below. Not sure if your plants have a magnesium deficiency? Read the article Nutrient deficiencies in marijuana plants for a list with pictures of all deficiencies.

    How to fix a magnesium deficiency

    fix magnesium deficiency cannabis

    There are several ways to resolve magnesium deficiency, but one of the better options is a product called Marijuana Booster.  This is one is very popular amongst marijuana growers because it is great for enhancing the quality of yields and provides a good balance of nutrients.

    More options are:

    • Dolomite lime
    • Magnesium sulfate
    • Garden lime
    • Worm castings
    • Epsom salts

    Since both Epsom salt and Magnesium sulfate (wiki) are water soluble, they work the best. For hydroponics systems, Epsom salts are by far the simplest solution. For every gallon of water in your tank add a teaspoon of Epsom salts. Give it a quarter of the initial dosage for every consecutive treatment. If you like, you can even add Calcium-Magnesium (available at this link for only $20)

    Magnesium and pH levels

    Magnesium ph levels weed

    If the pH of your plants roots get too low, the marijuana plant could display signs of magnesium deficiency, even more so in hydro (check these hydro ph levels). This occurs as a result of the pH of the roots not being at the right ratio, which causes the plant to not properly receive magnesium from the roots.

    Usually with this deficiency, the magnesium is there, but the roots are not able to receive the magnesium efficiently because of the wrong pH. This is why it is necessary to keep the right pH so as to prevent magnesium deficiency.

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    Providing additional magnesium to a system that has a pH lock-out will most likely not help since the plant can’t take in any magnesium until the pH is made right. If your plant has plenty of magnesium, giving it more could result in the development of other deficiencies by shutting out other nutrients the plant needs.

    If you’re growing marijuana in soil, magnesium is better received by the roots in the 6.0 – 7.0 pH rate. If your’re growing marijuana in hydro, magnesium is better received by the roots in the 6.0 – 6.5 pH rate.

    Try Flushing

    If suspicion sets in and you begin thinking you plant has a magnesium deficiency, flush the system with pure, pH’d water that has a normal dose of marijuana-friendly nutrients in it which should include magnesium. This serves to get rid of all nutrient salts that are may have damaged the plants ability to absorb magnesium and help replenish the pH to the right ratio.

    Read the article How to rinse a hydro system for more information about flusing

    List of marijuana plant symptoms

    Leaf Color: 
    – Edges Look Brown or Burnt
    – Pale Color Leaves
    – Lower and Older Leaves Turn Yellow
    – Yellowing Between Veins
    – Veins of Leaves Stay Green
    – Brown or Dark Spots
    – Speckled / Patchy Pattern

    Leaf Symptoms: 
    – Lower Leaves and Older Leaves Damaged
    – Leaf Tips Look Burnt
    – Leaf Tips Die
    – Yellowing Between Veins
    – Veins of Leaves Stay Green
    – Spots
    – Speckled / Patchy Pattern
    – Old Leaves Dropping Off
    – Twisted Growth
    – Leaves Curl Under
    – Leaves Curl Upwards
    – Withering / Drooping

    Plant Symptoms: 
    – Old Leaves Dropping Off
    – Twisted Growth
    – Leaves Curl Under
    – Leaves Curl Upwards
    – Plant Withering / Sagging

    Prevent deficiencies

    Prevent magnesium deficiency weed

    If you properly resolve the issue, the yellowing and discoloration of the leaves should cease almost instantly. Some damaged leaves could bounce back to a certain extent, but what matters the most is that you ensure the issue is not still spreading to the other leaves on the plant.

    We suggest not getting rid of the discolored leaves until you are certain the issue is totally resolved and is not spreading to the newer leaves. It is better if any continued discoloration occurs on the leaves that were already damaged.

    All in all, pay close attention to the growth of your plant and if you suspect any issues use the list of symptoms to determine if there is a deficiency. Once you have followed the proper steps to restore balance, remember that it may take a few days before the deficiency is completely cleared up.

    And remember that plants with strong genetics have less change of getting sick. Make sure you buy marijuana seeds from a trusted seedbank.

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    Thanks for reading. Please leave comments or questions below and don’t forget to download my free grow bible


    Avatar for Robert Bergman

    Robert Bergman

    Robert Bergman is an Amsterdam-based marijuana grow expert who has years of experience from small grows to massive operations. His passion for growing led him to develop his own Gold Leaf strain. Now, Robert is dedicated to sharing his knowledge with the world.... [Read full bio]


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